Forensic entomology
Encyclopedia
Forensic entomology is the application and study of insect
and other arthropod
biology to criminal matters. It is primarily associated with death investigations; however, it may also be used to detect drugs and poisons, determine the location of an incident, and find the presence and time of the infliction of wounds. Forensic entomology
can be divided into three subfields: urban, stored-product
and medico-legal/medico-criminal entomology.
, Francesco Redi
, Bergeret d’Arbois
, Jean Pierre Mégnin
and the German doctor Hermann Reinhard
have helped to lay the foundations for today's modern forensic entomology.
. The accepted theory of Redi's day claimed that maggots developed spontaneously from rotting meat. In an experiment, he used samples of rotting meat that were either fully exposed to the air, partially exposed to the air, or not exposed to air at all. Redi showed that both fully and partially exposed rotting meat developed fly maggots, whereas rotting meat that was not exposed to air did not develop maggots. This discovery completely changed the way people viewed the decomposition of organisms and prompted further investigations into insect life cycles and into entomology in general.
(1814–1893) was a French hospital physician, and was the first to apply forensic entomology to a case. In a case report published in 1855 he stated a general life cycle for insects and made many assumptions about their mating habits. Nevertheless these assumptions led him to the first application of forensic entomology in an estimation of post-mortem interval (PMI). His report used forensic entomology as tool to prove his hypothesis on how and when the person had died.
, a German medical doctor who played a vital role in the history of forensic entomology. He exhumed many bodies and demonstrated that the development of many different types of insect species could be tied to buried bodies. Reinhard conducted his first study in east Germany, and collected many Phorid flies from this initial study. He also concluded that the development of only some of the insects living with corpses underground were associated with them, since there were 15-year-old beetles who had little direct contact with them. Reinhard's works and studies were used extensively in further forensic entomology studies.
In this book he asserted that exposed corpses were subject to eight successional waves, whereas buried corpses were only subject to two waves. Mégnin made many great discoveries that helped shed new light on many of the general characteristics of decaying flora and fauna. Mégnin's work and study of the larval and adult forms of insect families found in cadavers sparked the interest of future entomologists and encouraged more research in the link between arthropods and the deceased, and thereby helped to establish the scientific discipline of forensic entomology.
s eggs appear, their location on the body and in what order they appear. This can be helpful in determining a post mortem interval
(PMI) and location of a death
in question. Since many insects exhibit a degree of endemism (occurring only in certain places), or have a well-defined phenology
(active only at a certain season, or time of day), their presence in association with other evidence can demonstrate potential links to times and locations where other events may have occurred). Another area covered by medicolegal forensic entomology is the relatively new field of entomotoxicology
. This particular branch involves the utilization of entomological specimens found at a scene in order to test for different drugs that may have possibly played a role in the death of the victim.
The order in which insects feed on a corpse is known as faunal succession.
(order diptera
) are often first on the scene. They prefer a moist corpse for their offspring (maggots) to feed on. The most significant types of fly include:
• Larvae feed on decaying bodies
• Some species can burrow to a depth of 50cm over 4 days
• Important in buried bodies
s (Order Coleoptera) are generally found on the corpse when it is more decomposed . In drier conditions, the beetles can be replaced by moth flies (Psychodidae
).
s (class Acari) feed on corpses with Macrocheles mites common in the early stages of decomposition, while Tyroglyphidae and Oribatidae mites such as Rostrozetes feed on dry skin in the later stages of decomposition.
Nicrophorus beetles often carry on their bodies the mite Poecilochirus
which feed on fly eggs. If they arrive at the corpse before any fly eggs hatch into maggots, the first eggs are eaten and maggot development is delayed. This may lead to incorrect PMI estimates. Nicrophorus beetles find the ammonia
excretions of blowfly maggots toxic, and the Poecilochirus mites, by keeping the maggot population low, allow Nicrophorus to occupy the corpse.
s (Order Lepidoptera
) specifically clothes-moths – Family Tineidae
– are closely related to butterflies
. Most species of moth are nocturnal, but there are crepuscular
and diurnal species. Moths feed on mammalian hair during their larval stages and may forage on any hair that remains on a body. They are amongst the final animals contributing to the decomposition of a corpse.
) are not necessarily necrophagous. While some feed on the body, some are also predatory, and eat the insects feeding on the body. Bee
s and wasp
s have been seen feeding on the body during the early stages. This may cause problems for murder cases in which larval flies are used to estimate the post mortem interval since eggs and larvae on the body may have been consumed prior to the arrival on scene of investigators.
Forensic entomologists have used bees in several cases where parents have used bees to sting their children as a form of discipline. Also, entomologists have been called upon to determine whether or not bees or wasps have been the cause of an accident. Whether through their presence or by stinging it has be speculated that these insects have been the cause of numerous automobile accidents.
levels in the area where the body is found can affect the time for insect development. In most species, large amounts of rain will indirectly cause slower development due to drop in temperature. Light rain or a very humid environment, by acting as an insulator, will permit a greater core temperature within the maggot mass, resulting in faster development.
, was assigned to a case involving the discovery of a decomposing body found on a boat half a mile from shore. Upon collection of the maggot mass, only one insect, Chrysomya megacephala, was discovered. He concluded that the water barrier accounted for the scarcity of other flies. He also noted that flies will not attempt to trek across large bodies of water unless there is a substantially influential attractant.
In addition, the amount of time a maggot mass has been exposed to salt water can affect its development. From the cases Goff observed he found that if subjected for more than 30 minutes, there was a 24 hour developmental delay. Unfortunately, not many more studies have been conducted and thus a specific amount of delay time is difficult to estimate.
Bodies exposed to large amounts of sunlight will heat up, giving the insects a warmer area to develop, reducing their development time.
An experiment conducted by Bernard Greenberg and John Charles Kunich with the use of rabbit carcasses to study accumulation of degree days found that with temperature ranging in the mid 70s to high 80s the amount of deveopmental time for maggots was significantly reduced.
In contrast, bodies found in shaded areas will be cooler, and insects will require longer growth periods. In addition, if temperatures reach extreme levels of cold, insects instinctively know to prolong their development time in order to hatch into a more accepting and viable climate in order to increase the chance of survival and reproduction.
As the body begins to decompose, a compilation of fluids will leak to the ground. In this area most of the expected fauna can be found. Also, it is more likely that rove beetles and other non-flying insects will be found here instead of directly on the body. Fly maggots, initially deposited on the body, may also be found below.
's book La Faune des Cadavres there are eight distinct faunal successions attracted to a corpse. While most beetle
s and flies
of forensic importance can be found worldwide, a portion of them are limited to a specific range of habitats. It is forensically important to know the geographical distribution of these insects is order to determine information such as post mortem interval or whether a body has been moved from its original place of death.
Calliphoridae is arguably the most important family concerning forensic entomology given that they are the first to arrive on the corpse. The family’s habitat ranges into the southern portion of the United States
. However, while Chrysomya rufifaces, the hairy maggot blow fly, is part of the Calliphoridae family and is widespread, it is not prevalent in the Southern California
, Arizona
, New Mexico
, Louisiana
, Florida
, or Illinois
regions.
Flesh flies fall under the family Sacrophagidae and generally arrive to a corpse following Calliphoridae. However, as previously mentioned they are capable of flying in the rain. This key advantage enables them to occasionally reach a body before Calliphoridae overall effecting the maggot mass that will be discovered. Flesh flies are globally distributed including habitats in the United States, Europe, Asia, and the Middle East.
Beetles are representative of the order Coleoptera which accounts for the largest of the insect orders. Beetles are very adaptive and can be found in almost all environments with the exception of Antarctica and high mountainous regions. The most diverse beetle fauna can be found in the tropics. In addition, beetles are less submissive to temperatures. Thus, if a carcass has been found in cold temperatures, the beetle will be prevalent over Calliphoridae.
Damp weather causes reproduction and growth enhancement in many insect types, especially when coupled with warm temperatures. Most pests concerned at this time are ant
s, spider
s, cricket
s, cockroach
es, ladybugs, yellowjacket
s, hornet
s, mice
, and rat
s.
When conditions are dry, the deprivation of moisture outside drives many pests inside searching for water. While the rainy weather increases the numbers of insects, this dry weather causes pest invasions to increase. The pests most commonly known during dry conditions are scorpion
s, ants, pillbugs, millipede
s, crickets, and spiders. Extreme drought does kill many populations of insects, but also drives surviving insects to invade more often.
Cold temperatures outside will cause invasions beginning in the late summer months and early fall. Box elder bugs, cluster flies
, ladybugs, and silverfish
are noticed some of the most common insects to seek the warm indoors.
, or reevaluate at old information. The use of these newly developed techniques and evaluations have become relevant in litigation and appeals. Forensic entomology not only uses arthropod biology, but it pulls from other sciences, introducing fields like chemistry and genetics, exploiting their inherent synergy through the use of DNA in forensic entomology
.
(SEM) to identify key morphological features of eggs and maggots. Some of the morphological differences that can help identify the different species are the presence/absence of anastomosis, the presence/absence of holes, and the shape and length of the median area.
The SEM method provides an array of morphological features for use in identifying fly eggs; however, this method does have some disadvantages. The main disadvantage is that it requires expensive equipment and can take time to identify the species from which the egg originated, so it may not be useful in a field study or to quickly identify a particular egg. The SEM method is effective provided there is ample time and the proper equipment and the particular fly eggs are plentiful. The ability to use these morphological differences gives forensic entomologists a powerful tool that can help with estimating a post mortem interval, along with other relevant information, such as whether the body has been disturbed post mortem.
staining. The collected eggs are rinsed with a normal saline
solution and placed in a glass petri dish. The eggs are soaked in a 1% potassium permanganate solution for one minute and then dehydrated and mounted onto a slide for observation. These slides can be used with any light microscope
with a calibrated eyepiece to compare various morphological features. The most important and useful features for identifying eggs are the size, length, and width of the plastron, as well as the morphology of the plastron in the area around the micropyle. The various measurements and observations when compared to standards for forensically important species are used to determine the species of the egg.
to differentiate between different species of the subfamily Chrysomyinae. This is particularly useful when working to determine the identity of specimens that do not have distinctive morphological characteristics at certain life stages.
. Three genes were measured in an experiment with Drosophila melanogaster: bicoid (bcd), slalom (sll), and chitin synthase (cs). These three genes were used because they are likely to be in varied levels during different times of the egg development process. These genes all share a linear relationship in regards to age of the egg; that is, the older the egg is the more of the particular gene is expressed. However, all of the genes are expressed in varying amounts. Different genes on different loci would need to be selected for another fly species. The genes expressions are mapped in a control sample to formulate a developmental chart of the gene expression at certain time intervals. This chart can then be compared to the measured values of gene expression to accurately predict the age of an egg to within two hours with a high confidence level
. Even though this technique can be used to estimate the age of an egg, the feasibility and legal acceptance of this must be considered for it to be a widely utilized forensic technique. One benefit of this would be that it is like other DNA-based techniques so most labs would be equipped to conduct similar experiments without requiring new capital investment. This style of age determination is in the process of being used to more accurately find the age of the instars and pupa; however, it is much more complicated, as there are more genes being expressed during these stages. The hope is that with this and other similar techniques a more accurate PMI can be obtained.
revealed the following results on decay and insect colonization.
stygia, which lasted until day 27. The larvae of Chrysomya rufifacies
were present between the day 13 and day 47. The H. rostrata, larvae of Lucilia sericata, Psychodidae
family, and sylvicola were found to occur relatively late in the body's decay.
and Piophilidae (no larvae from this family were obtained in recovery).
stages.
Early twentieth-century popular scientific literature began to pique a broader interest in entomology
. The very popular ten-volume book series, Alfred Brehem’s Thierleben (Life of Animals, 1876–1879) expounded on many zoological topics, including arthropods. The accessible writing style of French entomologist Jean-Henri Fabre was also instrumental in the popularization of entomology. His collection of writings Souvenirs Entomologique, written during the last half of the 19th century, is especially useful because of the meticulous attention to detail to the observed insects’ behaviors and life cycles.
The real impetus behind the modern cultural fascination with solving crime using entomological evidence can be traced back to the works Faune de Tombeaux (Fauna of the Tomb, 1887) and Les Faunes des Cadavres (Fauna of the Cadaver, 1894) by French veterinarian
and entomologist Jean Pierre Mégnin
. These works made the concept of the process of insect ecological succession on a corpse understandable and interesting to an ordinary reader in a way that no other previous scientific work had done. It was after the publication of Mégnin’s work that the studies of forensic science and entomology became an established part of Western popular culture, which in turn inspired other scientists to continue and expand upon his research.
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
and other arthropod
Arthropod
An arthropod is an invertebrate animal having an exoskeleton , a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda , and include the insects, arachnids, crustaceans, and others...
biology to criminal matters. It is primarily associated with death investigations; however, it may also be used to detect drugs and poisons, determine the location of an incident, and find the presence and time of the infliction of wounds. Forensic entomology
Entomology
Entomology is the scientific study of insects, a branch of arthropodology...
can be divided into three subfields: urban, stored-product
Home stored product entomology
Home stored product entomology is the study of insects which infest foodstuffs stored in the home. It deals with the prevention, detection and eradication of the pests...
and medico-legal/medico-criminal entomology.
History
Historically, there have been several accounts of applications for, and experimentation with, forensic entomology. The concept of forensic entomology dates back to at least the 14th century. However, only in the last 30 years has forensic entomology been systematically explored as a feasible source for evidence in criminal investigations. Through their own experiments and interest in arthropods and death, Song CiSong Ci
Song Ci was a forensic medical expert active during the Southern Song Dynasty who wrote a groundbreaking book titled Collected Cases of Injustice Rectified ....
, Francesco Redi
Francesco Redi
Francesco Redi was an Italian physician, naturalist, and poet.-Biography:The son of Gregorio Redi and Cecilia de Ghinci was born in Arezzo on February 18, 1626. After schooling with the Jesuits, he attended the University of Pisa...
, Bergeret d’Arbois
Louis François Etienne Bergeret
Louis François Etienne Bergeret also Bergeret d’Arbois was a French physician.Bergeret worked at theHopital Civil d’ Arbois.He was a friend of Louis Pasteur...
, Jean Pierre Mégnin
Jean Pierre Mégnin
Jean Pierre Mégnin was a French army veterinarian and entomologist. He is best known for his work with dogs and forensic entomology....
and the German doctor Hermann Reinhard
Hermann Reinhard
Hermann Reinhard was a German physician and entomologist. He specialised in Hymenoptera ....
have helped to lay the foundations for today's modern forensic entomology.
Song Ci
Song Ci (also known as Sung Tz’u) was a Judicial Intendant who lived in China in the late 13th century. In 1247 AD Song Ci wrote a book entitled Washing Away of Wrongs as a handbook for coroners. In this book Song Ci depicts several cases in which he took notes on how a person died and elaborates on probable causes. He goes into detail on how to examine a corpse both before and after burial. He also explains the process of how to determine a probable cause of death. The purpose of this book was to be used as a guide for other investigators so they could assess the scene of the crime effectively. His level of detail in explaining what he observed in all his cases laid down the fundamentals for modern forensic entomologists and is the first recorded account in history of someone using forensic entomology for judicial means.Francesco Redi
In 1668, Italian physician Francesco Redi disproved the theory of spontaneous generationSpontaneous generation
Spontaneous generation or Equivocal generation is an obsolete principle regarding the origin of life from inanimate matter, which held that this process was a commonplace and everyday occurrence, as distinguished from univocal generation, or reproduction from parent...
. The accepted theory of Redi's day claimed that maggots developed spontaneously from rotting meat. In an experiment, he used samples of rotting meat that were either fully exposed to the air, partially exposed to the air, or not exposed to air at all. Redi showed that both fully and partially exposed rotting meat developed fly maggots, whereas rotting meat that was not exposed to air did not develop maggots. This discovery completely changed the way people viewed the decomposition of organisms and prompted further investigations into insect life cycles and into entomology in general.
Bergeret d'Arbois
Dr Louis François Etienne BergeretLouis François Etienne Bergeret
Louis François Etienne Bergeret also Bergeret d’Arbois was a French physician.Bergeret worked at theHopital Civil d’ Arbois.He was a friend of Louis Pasteur...
(1814–1893) was a French hospital physician, and was the first to apply forensic entomology to a case. In a case report published in 1855 he stated a general life cycle for insects and made many assumptions about their mating habits. Nevertheless these assumptions led him to the first application of forensic entomology in an estimation of post-mortem interval (PMI). His report used forensic entomology as tool to prove his hypothesis on how and when the person had died.
Hermann Reinhard
The first systematic study in forensic entomology was conducted in 1881 by Hermann ReinhardHermann Reinhard
Hermann Reinhard was a German physician and entomologist. He specialised in Hymenoptera ....
, a German medical doctor who played a vital role in the history of forensic entomology. He exhumed many bodies and demonstrated that the development of many different types of insect species could be tied to buried bodies. Reinhard conducted his first study in east Germany, and collected many Phorid flies from this initial study. He also concluded that the development of only some of the insects living with corpses underground were associated with them, since there were 15-year-old beetles who had little direct contact with them. Reinhard's works and studies were used extensively in further forensic entomology studies.
Jean Pierre Mégnin
Jean Pierre Mégnin (1828–1905), an army veterinarian, published many articles and books on various subjects including the books Faune des Tombeaux and La Faune des Cadavres, which are considered to be among the most important forensic entomology books in history. In his second book he did revolutionary work on the theory of predictable waves, or successions of insects onto corpses. By counting numbers of live and dead mites that developed every 15 days and comparing this with his initial count on the infant, he was able to estimate how long that infant was dead.In this book he asserted that exposed corpses were subject to eight successional waves, whereas buried corpses were only subject to two waves. Mégnin made many great discoveries that helped shed new light on many of the general characteristics of decaying flora and fauna. Mégnin's work and study of the larval and adult forms of insect families found in cadavers sparked the interest of future entomologists and encouraged more research in the link between arthropods and the deceased, and thereby helped to establish the scientific discipline of forensic entomology.
Urban forensic entomology
Urban forensic entomology typically concerns pests infestations in buildings gardens or that may be the basis of litigation between private parties and service providers such as landlords or exterminators. Urban forensic entomology studies may also indicate the appropriateness of certain pesticide treatments and may also be used in stored products cases where it can help to determine chain of custody, when all points of possible infestation are examined in order to determine who is at fault.Stored-product forensic entomology
Stored-product forensic entomology is often used in litigation over insect infestation or contamination of commercially distributed foods.Medico-legal forensic entomology
Medicolegal forensic entomology covers evidence gathered through arthropod studies at the scenes of murder, suicide, rape, physical abuse and contraband trafficking. In murder investigations it deals with which insectInsect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s eggs appear, their location on the body and in what order they appear. This can be helpful in determining a post mortem interval
Post mortem interval
Post-mortem interval is the time that has elapsed since a person has died. If the time in question is not known, a number of medical/scientific techniques are used to determine it. This also can refer to the stage of decompostion the person is in....
(PMI) and location of a death
Death
Death is the permanent termination of the biological functions that sustain a living organism. Phenomena which commonly bring about death include old age, predation, malnutrition, disease, and accidents or trauma resulting in terminal injury....
in question. Since many insects exhibit a degree of endemism (occurring only in certain places), or have a well-defined phenology
Phenology
Phenology is the study of periodic plant and animal life cycle events and how these are influenced by seasonal and interannual variations in climate...
(active only at a certain season, or time of day), their presence in association with other evidence can demonstrate potential links to times and locations where other events may have occurred). Another area covered by medicolegal forensic entomology is the relatively new field of entomotoxicology
Entomotoxicology
In forensic entomology, entomotoxicology is the analysis of toxins in arthropods that feed on carrion. Using arthropods in a corpse or at a crime scene, investigators can determine whether toxins were present in a body at the time of death...
. This particular branch involves the utilization of entomological specimens found at a scene in order to test for different drugs that may have possibly played a role in the death of the victim.
Insect types
There are many different types of insect studied in forensic entomology. The insects listed below are mostly necrophagous (corpse-eating) and are particularly relevant to medicolegal entomological investigations. This is not a full list, as there are many variations due to climate.The order in which insects feed on a corpse is known as faunal succession.
Flies
FliesCalliphora latifrons
Calliphora latifrons is a species of blue bottle fly.This fly adheres to a particular environment and ecosystem that has limited geographic distributions in North America. Undisturbed, this environment fosters C. latifrons unique life cycle that somewhat differs from related blow flies...
(order diptera
Diptera
Diptera , or true flies, is the order of insects possessing only a single pair of wings on the mesothorax; the metathorax bears a pair of drumstick like structures called the halteres, the remnants of the hind wings. It is a large order, containing an estimated 240,000 species, although under half...
) are often first on the scene. They prefer a moist corpse for their offspring (maggots) to feed on. The most significant types of fly include:
- Blow flies – Family Calliphoridae- Flies in this family are often metallic in appearance and between ten to 12 mm in length. In addition to the name blow-fly, some members of this family are known as blue bottle flyCalliphora latifronsCalliphora latifrons is a species of blue bottle fly.This fly adheres to a particular environment and ecosystem that has limited geographic distributions in North America. Undisturbed, this environment fosters C. latifrons unique life cycle that somewhat differs from related blow flies...
, cluster flyCluster flyThe cluster flies are the genus Pollenia in the blowfly family Calliphoridae. Unlike more familiar blowflies such as the bluebottle genus Phormia, they do not present a health hazard because they do not lay eggs in human food. They are strictly parasitic on earthworms; the females lay their eggs...
, greenbottles, or black blowflyProtophormia terraenovaeProtophormia terraenovae is commonly called northern blowfly, blue-bottle fly or blue-assed fly. It is distinguished by its deep blue coloration and large size, is an important species throughout the northern hemisphere. This fly is notable for its economic impact as a myiasis pest of livestock...
. A characteristic of the blow-fly is its 3-segmented antennaeAntenna (biology)Antennae in biology have historically been paired appendages used for sensing in arthropods. More recently, the term has also been applied to cilium structures present in most cell types of eukaryotes....
. Hatching from an egg to the first larval stage takes from eight hours to one day. LarvaLarvaA larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
e have three stages of development (called instars); each stage is separated by a molting event. Worldwide, there are 1100 known species of blowflies, with 228 species in the Neotropics, and a large number of species in AfricaAfricaAfrica is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
and Southern EuropeEuropeEurope is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
. The most common area to find Calliphoridae species are in the countries of IndiaIndiaIndia , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
, JapanJapanJapan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
, Central AmericaCentral AmericaCentral America is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. When considered part of the unified continental model, it is considered a subcontinent...
, and in the southern United States. The typical habitat for blow-flies are temperate to tropical areas that provide a layer of loose, damp soil and litter where larvae may thrive and pupate. The forensic importance of this fly is that it is the first insectInsectInsects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
to come in contact with carrionCarrionCarrion refers to the carcass of a dead animal. Carrion is an important food source for large carnivores and omnivores in most ecosystems. Examples of carrion-eaters include vultures, hawks, eagles, hyenas, Virginia Opossum, Tasmanian Devils, coyotes, Komodo dragons, and burying beetles...
because they have the ability to smell death from up to ten miles (16 km) away.
- Flesh flies – Family Sarcophagidae- Most flesh flies breed in carrion, dung, or decaying material, but a few species lay their eggs in the open wounds of mammals; hence their common name. Characteristics of the flesh-fly is its 3-segmented antennaeAntenna (biology)Antennae in biology have historically been paired appendages used for sensing in arthropods. More recently, the term has also been applied to cilium structures present in most cell types of eukaryotes....
. They are medium-sized flies with black and gray longitudinal stripes on the thoraxThoraxThe thorax is a division of an animal's body that lies between the head and the abdomen.-In tetrapods:...
and checkering on the abdomenAbdomenIn vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity...
. Flesh-flies, being viviparous, frequently give birth to live young on corpses of human and other animals, at any stage of decomposition, from newly dead through to bloated or decaying (though the latter is more common). - House flyHouseflyThe housefly , Musca domestica, is a fly of the suborder Cyclorrhapha...
– Family MuscidaeMuscidaeMuscidae are a family of flies found in the superfamily Muscoidea. The apical segment of the antennae of Muscidae are plumose, and the basal portion is smooth....
- is the most common of all fliesFließFließ is a municipality in the Landeck district and is located5 km south of Landeck on the upper course of the Inn River. It has 9 hamlets and was already populated at the roman age; the village itself was founded around the 6th century. After a conflagration in 1933 Fließ was restored more...
found in homes, and indeed one of the most widely distributed insects; it is often considered a pest that can carry serious diseases. The adults are 6–9 mm long. Their thoraxThoraxThe thorax is a division of an animal's body that lies between the head and the abdomen.-In tetrapods:...
is gray, with four longitudinal dark lines on the back. The underside of their abdomen is yellow, and their whole body is covered with hair. Each female fly can lay up to 500 eggs in several batches of about 75 to 150 eggsEgg (biology)An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
. Genus HydrotaeaHydrotaeaHydrotaea are insects located in most regions of the world, but are more populous in warmer climates. They are often found on excrement in summer months, and are therefore generally found in close proximity to livestock. Among the 130 known species in this genus, the most commonly recognized is the...
are of particular forensic importance. - Cheese fliesCheese flyCheese flies are members of the family Piophilidae of flies. Most are scavengers in animal products and fungi. The best-known member of the family is Piophila casei. It is a small fly, about four mm long, found worldwide. The fly's larva infests cured meats, smoked fish, cheeses, and decaying...
– Family Piophilidae - Most are scavengers in animal products and fungi. The best-known member of the family is Piophila casei. It is a small fly, about four mm (1/6 inch) long, found worldwide. This fly's larva infests cured meats, smoked fish, cheeses, and decaying animals and is sometimes called the cheese skipper for its leaping ability. Forensic entomology uses the presence of Piophila casei larvae to help estimate the date of death for human remains. They do not take up residence in a corpse until three to six months after death. The adult fly's body is black, blue-black, or bronze, with some yellow on the head, antennae, and legs. The wings are faintly iridescent and lie flat upon the fly's abdomenAbdomenIn vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity...
when at rest. At four mm (1/6 inch) long, the fly is one-third to one-half as long as the common houseflyHouseflyThe housefly , Musca domestica, is a fly of the suborder Cyclorrhapha...
. - Coffin flies – Phoridae
- Lesser corpse flies – SphaeroceridaeSphaeroceridaeSphaeroceridae are a family of true flies in the order Diptera, often called small dung flies, lesser dung flies or lesser corpse flies due to their saprophagous habits. They belong to the typical fly suborder Brachycera as can be seen by their short antennae, and more precisely they are members of...
- Lesser house flies – FanniidaeFanniidaeThe Fanniidae are a small group of true flies largely confined to the Holarctic and temperate Neotropical regions.There are 11 Afrotropical species, 29 Oriental, and 14 Australasian. See Biogeographic Regions....
- Black scavenger flies – SepsidaeSepsidaeSepsidae are a family of flies, commonly called the black scavenger flies or ensign flies. There are approximately 250 species worldwide. They are usually found around dung or decaying plant and animal material. Many species resemble ants having a "waist" and glossy black body...
- Sun flies - HeleomyzidaeHeleomyzidaeHeleomyzidae is a small family of true flies in the insect order Diptera. There are over 650 described species of Heleomyzidae in about 80 genera and 22 tribes distributed throughout the world; the greatest number occur in the Holarctic Region. Approximately 100 species of Heleomyzidae are found in...
- Black soldier fly - StratiomyidaeStratiomyidaeThe soldier flies , are a family of flies . The family contains about 1,500 species in about 400 genera worldwide. Adults are found near larval habitats...
- have potential for use in forensic entomology. The larvae are common scavengers in compost heaps, are found in association with carrion, can be destructive pests in honey bee hives, and are used in manureManureManure is organic matter used as organic fertilizer in agriculture. Manures contribute to the fertility of the soil by adding organic matter and nutrients, such as nitrogen, that are trapped by bacteria in the soil...
management (for both house fly control and reduction in manure volume). The larvae range in size from 1/8 to 3/4 of an inch (3 to 19 millimeters). The adult fly is a mimicMimicIn evolutionary biology, mimicry is the similarity of one species to another which protects one or both. This similarity can be in appearance, behaviour, sound, scent and even location, with the mimics found in similar places to their models....
, very close in size, color, and appearance to the organ pipe mud dauberOrgan pipe mud dauberThe organ pipe mud dauber is a type of wasp in the family Crabronidae. They are fairly large wasps, shiny black with pale hind tarsi. Male organ pipe mud daubers are among the few male wasps of any species to stay at the nest...
wasp and its relatives. - Phoridae – Humpbacked flies
• Larvae feed on decaying bodies
• Some species can burrow to a depth of 50cm over 4 days
• Important in buried bodies
Beetles
BeetleBeetle
Coleoptera is an order of insects commonly called beetles. The word "coleoptera" is from the Greek , koleos, "sheath"; and , pteron, "wing", thus "sheathed wing". Coleoptera contains more species than any other order, constituting almost 25% of all known life-forms...
s (Order Coleoptera) are generally found on the corpse when it is more decomposed . In drier conditions, the beetles can be replaced by moth flies (Psychodidae
Psychodidae
The nematoceran family Psychodidae are small true flies with short, hairy bodies and wings giving them a "furry" moth-like appearance...
).
- Rove beetles – family Staphylinidae – are elongate beetles with small elytra (wing covers) and large jaws. Like other beetles inhabiting carrion, they have fast larval development with only three larval stages. Creophilus species are common predators of carrion, and since they are large, are a very visible component of the fauna of corpses. Some adult Staphylinidae are early visitors to a corpse, feeding on larvae of all species of fly, including the later predatory fly larvae. They lay their eggs in the corpse, and the emerging larvae are also predators. Some species have a long development time in the egg, and are common only during the later stages of decomposition. Staphylinids can also tear open the pupaPupaA pupa is the life stage of some insects undergoing transformation. The pupal stage is found only in holometabolous insects, those that undergo a complete metamorphosis, going through four life stages; embryo, larva, pupa and imago...
l cases of flies, to sustain themselves at a corpse for long periods. - Hister beetles – family Histeridae. Adult histerids are usually shiny beetles (black or metallic-green) which have an introverted head. The carrion-feeding species only become active at night when they enter the maggot-infested part of the corpse to capture and devour their maggot prey. During daylight they hide under the corpse unless it is sufficiently decayed to enable them to hide inside it. They have fast larval development with only two larval stages. Among the first beetles to arrive at a corpse are Histeridae of the genus Saprinus. Saprinus adults feed on both the larvae and pupae of blowflies, although some have a preference for fresh pupae. The adults lay their eggs in the corpse, inhabiting it in the later stages of decay.
- Carrion beetles – family Silphidae- Adult Silphidae have an average size of about 12 mm. They are also referred to as burying beetles because they dig and bury small carcasses underground. Both parents tend to their young and exhibit communial breeding. The male carrion beetle's job in care is to provide protection for the breed and carcass from competitors.
- Ham beetles – family CleridaeCleridaeCleridae are a family of beetles of the superfamily Cleroidea. They are commonly known as checkered beetles. The Cleridae family has a worldwide distribution, and a variety of habitats and feeding preferences....
- Carcass beetles – family Trogidae
- Skin/hide beetles – family Dermestidae. Hide beetles are important in the final stages of decomposition of a carcass. The adults and larvae feed on the dried skin, tendons and bone left by fly larvae. Hide beetles are the only beetle with the enzymes necessary for breaking down keratinKeratinKeratin refers to a family of fibrous structural proteins. Keratin is the key of structural material making up the outer layer of human skin. It is also the key structural component of hair and nails...
, a protein component of hair. - Scarab beetles – family ScarabaeidaeScarabaeidaeThe family Scarabaeidae as currently defined consists of over 30,000 species of beetles worldwide. The species in this large family are often called scarabs or scarab beetles. The classification of this family is fairly unstable, with numerous competing theories, and new proposals appearing quite...
- Scarab beetles may be any one of around 30,000 beetle species worldwide that are compact, heavy-bodied and oval in shape. The flattened plates, which each antenna terminates, are fitted together to form a club. The outer edges of the front legs may also be toothed or scalloped. Scarab beetles range from 0.2 to 4.8 in (5.1 to 121.9 mm) in length. These species are known for being one of the heaviest insect species. - Sap beetles – family Nitidulidae
Mites
Many miteMite
Mites, along with ticks, are small arthropods belonging to the subclass Acari and the class Arachnida. The scientific discipline devoted to the study of ticks and mites is called acarology.-Diversity and systematics:...
s (class Acari) feed on corpses with Macrocheles mites common in the early stages of decomposition, while Tyroglyphidae and Oribatidae mites such as Rostrozetes feed on dry skin in the later stages of decomposition.
Nicrophorus beetles often carry on their bodies the mite Poecilochirus
Poecilochirus
Poecilochirus is a genus of mites in the family Parasitidae. They feed on fly eggs and larva. At least 14 species of the genus are carried from one food source to another by beetles of multiple genuses in the family Silphidae with whom they often have a symbiotic relationship in protecting the...
which feed on fly eggs. If they arrive at the corpse before any fly eggs hatch into maggots, the first eggs are eaten and maggot development is delayed. This may lead to incorrect PMI estimates. Nicrophorus beetles find the ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...
excretions of blowfly maggots toxic, and the Poecilochirus mites, by keeping the maggot population low, allow Nicrophorus to occupy the corpse.
Moths
MothMoth
A moth is an insect closely related to the butterfly, both being of the order Lepidoptera. Moths form the majority of this order; there are thought to be 150,000 to 250,000 different species of moth , with thousands of species yet to be described...
s (Order Lepidoptera
Lepidoptera
Lepidoptera is a large order of insects that includes moths and butterflies . It is one of the most widespread and widely recognizable insect orders in the world, encompassing moths and the three superfamilies of butterflies, skipper butterflies, and moth-butterflies...
) specifically clothes-moths – Family Tineidae
Tineidae
Tineidae is a family of moths in the order Lepidoptera. Collectively, they are known as fungus moths or tineid moths. The family contains considerably more than 3,000 species in over 300 genera. Most of the tineid moths are small or medium-sized, with wings held roofwise over the body at rest...
– are closely related to butterflies
Butterfly
A butterfly is a mainly day-flying insect of the order Lepidoptera, which includes the butterflies and moths. Like other holometabolous insects, the butterfly's life cycle consists of four parts: egg, larva, pupa and adult. Most species are diurnal. Butterflies have large, often brightly coloured...
. Most species of moth are nocturnal, but there are crepuscular
Crepuscular
Crepuscular animals are those that are active primarily during twilight, that is during dawn and dusk. The word is derived from the Latin word crepusculum, meaning "twilight." Crepuscular is, thus, in contrast with diurnal and nocturnal behavior. Crepuscular animals may also be active on a bright...
and diurnal species. Moths feed on mammalian hair during their larval stages and may forage on any hair that remains on a body. They are amongst the final animals contributing to the decomposition of a corpse.
Wasps, ants, and bees
Wasps, ants, and bees (Order HymenopteraHymenoptera
Hymenoptera is one of the largest orders of insects, comprising the sawflies, wasps, bees and ants. There are over 130,000 recognized species, with many more remaining to be described. The name refers to the heavy wings of the insects, and is derived from the Ancient Greek ὑμήν : membrane and...
) are not necessarily necrophagous. While some feed on the body, some are also predatory, and eat the insects feeding on the body. Bee
Bee
Bees are flying insects closely related to wasps and ants, and are known for their role in pollination and for producing honey and beeswax. Bees are a monophyletic lineage within the superfamily Apoidea, presently classified by the unranked taxon name Anthophila...
s and wasp
Wasp
The term wasp is typically defined as any insect of the order Hymenoptera and suborder Apocrita that is neither a bee nor an ant. Almost every pest insect species has at least one wasp species that preys upon it or parasitizes it, making wasps critically important in natural control of their...
s have been seen feeding on the body during the early stages. This may cause problems for murder cases in which larval flies are used to estimate the post mortem interval since eggs and larvae on the body may have been consumed prior to the arrival on scene of investigators.
- Wasps – (particularly family Vespidae). Wasps exhibit a range of social difficulty, from private living to eusocial colonies. The non-breeding creature cares for the young or defend and supply for the group. Wasps are commentable for studies of evolutionary origin and maintenance of social behavior in animals.
- Ants – Family FormicidaeAntAnts are social insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from wasp-like ancestors in the mid-Cretaceous period between 110 and 130 million years ago and diversified after the rise of flowering plants. More than...
. Among the most widespread and damaging of introduced species are ants. Many ants share some characteristics that ease their preamble, institution, and subsequent range expansion. One feature of their importance is the ability to establish numerically large, ecologically dominant colonies.
- Bees – Superfamily ApoideaApoideaThe superfamily Apoidea is a major group within the Hymenoptera, which includes two traditionally-recognized lineages, the "sphecoid" wasps, and the bees, who appear to be their descendants.- Nomenclature :...
.
Forensic entomologists have used bees in several cases where parents have used bees to sting their children as a form of discipline. Also, entomologists have been called upon to determine whether or not bees or wasps have been the cause of an accident. Whether through their presence or by stinging it has be speculated that these insects have been the cause of numerous automobile accidents.
Moisture levels
Rain and humidityHumidity
Humidity is a term for the amount of water vapor in the air, and can refer to any one of several measurements of humidity. Formally, humid air is not "moist air" but a mixture of water vapor and other constituents of air, and humidity is defined in terms of the water content of this mixture,...
levels in the area where the body is found can affect the time for insect development. In most species, large amounts of rain will indirectly cause slower development due to drop in temperature. Light rain or a very humid environment, by acting as an insulator, will permit a greater core temperature within the maggot mass, resulting in faster development.
Bodies of water
M. Lee Goff, a noted and well respected forensic entomologistForensic entomologist
Forensic entomologists are those involved in the branch of entomology that involves insects and violent crime or the law, known as forensic entomology. This includes three main branches: medicocriminal entomology, urban entomology, and stored product entomology...
, was assigned to a case involving the discovery of a decomposing body found on a boat half a mile from shore. Upon collection of the maggot mass, only one insect, Chrysomya megacephala, was discovered. He concluded that the water barrier accounted for the scarcity of other flies. He also noted that flies will not attempt to trek across large bodies of water unless there is a substantially influential attractant.
In addition, the amount of time a maggot mass has been exposed to salt water can affect its development. From the cases Goff observed he found that if subjected for more than 30 minutes, there was a 24 hour developmental delay. Unfortunately, not many more studies have been conducted and thus a specific amount of delay time is difficult to estimate.
Sun exposure
"Because insects are cold-blooded animals, their rate of development is more or less dependent on ambient temperature."Bodies exposed to large amounts of sunlight will heat up, giving the insects a warmer area to develop, reducing their development time.
An experiment conducted by Bernard Greenberg and John Charles Kunich with the use of rabbit carcasses to study accumulation of degree days found that with temperature ranging in the mid 70s to high 80s the amount of deveopmental time for maggots was significantly reduced.
In contrast, bodies found in shaded areas will be cooler, and insects will require longer growth periods. In addition, if temperatures reach extreme levels of cold, insects instinctively know to prolong their development time in order to hatch into a more accepting and viable climate in order to increase the chance of survival and reproduction.
Air exposure
Hanged bodies can be expected to show their own quantity and variety of flies. Also, the amount of time flies will stay on a hanged body will vary in comparison to one found on the ground. A hanged body is more exposed to air and thus will dry out faster leaving less food source for the maggots.As the body begins to decompose, a compilation of fluids will leak to the ground. In this area most of the expected fauna can be found. Also, it is more likely that rove beetles and other non-flying insects will be found here instead of directly on the body. Fly maggots, initially deposited on the body, may also be found below.
Geography
According to Jean Pierre MégninJean Pierre Mégnin
Jean Pierre Mégnin was a French army veterinarian and entomologist. He is best known for his work with dogs and forensic entomology....
's book La Faune des Cadavres there are eight distinct faunal successions attracted to a corpse. While most beetle
Beetle
Coleoptera is an order of insects commonly called beetles. The word "coleoptera" is from the Greek , koleos, "sheath"; and , pteron, "wing", thus "sheathed wing". Coleoptera contains more species than any other order, constituting almost 25% of all known life-forms...
s and flies
Fly
True flies are insects of the order Diptera . They possess a pair of wings on the mesothorax and a pair of halteres, derived from the hind wings, on the metathorax...
of forensic importance can be found worldwide, a portion of them are limited to a specific range of habitats. It is forensically important to know the geographical distribution of these insects is order to determine information such as post mortem interval or whether a body has been moved from its original place of death.
Calliphoridae is arguably the most important family concerning forensic entomology given that they are the first to arrive on the corpse. The family’s habitat ranges into the southern portion of the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
. However, while Chrysomya rufifaces, the hairy maggot blow fly, is part of the Calliphoridae family and is widespread, it is not prevalent in the Southern California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
, Arizona
Arizona
Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...
, New Mexico
New Mexico
New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
, Louisiana
Louisiana
Louisiana is a state located in the southern region of the United States of America. Its capital is Baton Rouge and largest city is New Orleans. Louisiana is the only state in the U.S. with political subdivisions termed parishes, which are local governments equivalent to counties...
, Florida
Florida
Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...
, or Illinois
Illinois
Illinois is the fifth-most populous state of the United States of America, and is often noted for being a microcosm of the entire country. With Chicago in the northeast, small industrial cities and great agricultural productivity in central and northern Illinois, and natural resources like coal,...
regions.
Flesh flies fall under the family Sacrophagidae and generally arrive to a corpse following Calliphoridae. However, as previously mentioned they are capable of flying in the rain. This key advantage enables them to occasionally reach a body before Calliphoridae overall effecting the maggot mass that will be discovered. Flesh flies are globally distributed including habitats in the United States, Europe, Asia, and the Middle East.
Beetles are representative of the order Coleoptera which accounts for the largest of the insect orders. Beetles are very adaptive and can be found in almost all environments with the exception of Antarctica and high mountainous regions. The most diverse beetle fauna can be found in the tropics. In addition, beetles are less submissive to temperatures. Thus, if a carcass has been found in cold temperatures, the beetle will be prevalent over Calliphoridae.
Weather
Various weather conditions in a given amount of time cause certain pests to invade human households. This is because the insects are in search of food, water, and shelter.Damp weather causes reproduction and growth enhancement in many insect types, especially when coupled with warm temperatures. Most pests concerned at this time are ant
Ant
Ants are social insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from wasp-like ancestors in the mid-Cretaceous period between 110 and 130 million years ago and diversified after the rise of flowering plants. More than...
s, spider
Spider
Spiders are air-breathing arthropods that have eight legs, and chelicerae with fangs that inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all other groups of organisms...
s, cricket
Cricket (insect)
Crickets, family Gryllidae , are insects somewhat related to grasshoppers, and more closely related to katydids or bush crickets . They have somewhat flattened bodies and long antennae. There are about 900 species of crickets...
s, cockroach
Cockroach
Cockroaches are insects of the order Blattaria or Blattodea, of which about 30 species out of 4,500 total are associated with human habitations...
es, ladybugs, yellowjacket
Yellowjacket
Yellowjacket is the common name in North America for predatory wasps of the genera Vespula and Dolichovespula. Members of these genera are known simply as "wasps" in other English-speaking countries...
s, hornet
Hornet
Hornets are the largest eusocial wasps; some species can reach up to in length. The true hornets make up the genus Vespa and are distinguished from other vespines by the width of the vertex , which is proportionally larger in Vespa and by the anteriorly rounded gasters .- Life cycle :In...
s, mice
Mouse
A mouse is a small mammal belonging to the order of rodents. The best known mouse species is the common house mouse . It is also a popular pet. In some places, certain kinds of field mice are also common. This rodent is eaten by large birds such as hawks and eagles...
, and rat
Rat
Rats are various medium-sized, long-tailed rodents of the superfamily Muroidea. "True rats" are members of the genus Rattus, the most important of which to humans are the black rat, Rattus rattus, and the brown rat, Rattus norvegicus...
s.
When conditions are dry, the deprivation of moisture outside drives many pests inside searching for water. While the rainy weather increases the numbers of insects, this dry weather causes pest invasions to increase. The pests most commonly known during dry conditions are scorpion
Scorpion
Scorpions are predatory arthropod animals of the order Scorpiones within the class Arachnida. They have eight legs and are easily recognized by the pair of grasping claws and the narrow, segmented tail, often carried in a characteristic forward curve over the back, ending with a venomous stinger...
s, ants, pillbugs, millipede
Millipede
Millipedes are arthropods that have two pairs of legs per segment . Each segment that has two pairs of legs is a result of two single segments fused together as one...
s, crickets, and spiders. Extreme drought does kill many populations of insects, but also drives surviving insects to invade more often.
Cold temperatures outside will cause invasions beginning in the late summer months and early fall. Box elder bugs, cluster flies
Cluster fly
The cluster flies are the genus Pollenia in the blowfly family Calliphoridae. Unlike more familiar blowflies such as the bluebottle genus Phormia, they do not present a health hazard because they do not lay eggs in human food. They are strictly parasitic on earthworms; the females lay their eggs...
, ladybugs, and silverfish
Silverfish
Lepisma saccharina, frequently called silverfish, fishmoths, carpet sharks or paramites, are small, wingless insects in the order Thysanura...
are noticed some of the most common insects to seek the warm indoors.
Modern techniques
Many new techniques have been developed and are used in order to more accurately gather evidenceEntomological evidence collection
Entomological evidence collection is the process of collecting evidence based on insect clues to be used in criminal investigations. If evidence is not carefully preserved at a crime scene after a death, it may be difficult or impossible for an entomologist to make an accurate identification of...
, or reevaluate at old information. The use of these newly developed techniques and evaluations have become relevant in litigation and appeals. Forensic entomology not only uses arthropod biology, but it pulls from other sciences, introducing fields like chemistry and genetics, exploiting their inherent synergy through the use of DNA in forensic entomology
Use of DNA in forensic entomology
Forensic entomology contains three aspects: medicocriminal entomology, urban entomology, and stored product entomology. This article focuses more on the medicocriminal aspect and how DNA is analyzed with various blood feeding insects.- Blood meal extraction :...
.
Scanning electron microscopy
Fly larvae and fly egss are used to aid in the determination of a PMI. In order for the data to be useful the larvae and eggs must be identified down to a species level to get an accurate estimate for the PMI. There are many techniques currently being developed to differentiate between the various species of forensically important insects. A study in 2007 demonstrates a technique that can use scanning electron microscopyScanning electron microscope
A scanning electron microscope is a type of electron microscope that images a sample by scanning it with a high-energy beam of electrons in a raster scan pattern...
(SEM) to identify key morphological features of eggs and maggots. Some of the morphological differences that can help identify the different species are the presence/absence of anastomosis, the presence/absence of holes, and the shape and length of the median area.
The SEM method provides an array of morphological features for use in identifying fly eggs; however, this method does have some disadvantages. The main disadvantage is that it requires expensive equipment and can take time to identify the species from which the egg originated, so it may not be useful in a field study or to quickly identify a particular egg. The SEM method is effective provided there is ample time and the proper equipment and the particular fly eggs are plentiful. The ability to use these morphological differences gives forensic entomologists a powerful tool that can help with estimating a post mortem interval, along with other relevant information, such as whether the body has been disturbed post mortem.
Potassium permanganate staining
When scanning electron microscopy is not available, a faster, lower cost technique is potassium permanganatePotassium permanganate
Potassium permanganate is an inorganic chemical compound with the formula KMnO4. It is a salt consisting of K+ and MnO4− ions. Formerly known as permanganate of potash or Condy's crystals, it is a strong oxidizing agent. It dissolves in water to give intensely purple solutions, the...
staining. The collected eggs are rinsed with a normal saline
Saline (medicine)
In medicine, saline is a general term referring to a sterile solution of sodium chloride in water but is only sterile when it is to be placed intravenously, otherwise, a saline solution is a salt water solution...
solution and placed in a glass petri dish. The eggs are soaked in a 1% potassium permanganate solution for one minute and then dehydrated and mounted onto a slide for observation. These slides can be used with any light microscope
Optical microscope
The optical microscope, often referred to as the "light microscope", is a type of microscope which uses visible light and a system of lenses to magnify images of small samples. Optical microscopes are the oldest design of microscope and were possibly designed in their present compound form in the...
with a calibrated eyepiece to compare various morphological features. The most important and useful features for identifying eggs are the size, length, and width of the plastron, as well as the morphology of the plastron in the area around the micropyle. The various measurements and observations when compared to standards for forensically important species are used to determine the species of the egg.
Mitochondrial DNA
In 2001, a method was devised by Jeffrey Wells and Felix Sperling to use mitochondrial DNAMitochondrial DNA
Mitochondrial DNA is the DNA located in organelles called mitochondria, structures within eukaryotic cells that convert the chemical energy from food into a form that cells can use, adenosine triphosphate...
to differentiate between different species of the subfamily Chrysomyinae. This is particularly useful when working to determine the identity of specimens that do not have distinctive morphological characteristics at certain life stages.
Mock crime scenes
A valuable tool that is becoming very common in the training of forensic entomologists is the use of mock crime scenes using pig carcasses. The pig carcass represents a human body and can be used to illustrate various environmental effects on both arthropod succession and the estimate of the post mortem interval.Gene expression studies
Although physical characteristics and sizes at various instars have been used to estimate fly age, a more recent study has been conducted to determine the age of an egg based on the expression of particular genes. This is particularly useful in determining developmental stages that are not evidenced by change in size; such as the egg or pupa and where only a general time interval can be estimated based on the duration of the particular developmental stage. This is done by breaking the stages down into smaller units separated by predictable changed in gene expressionGene expression
Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product. These products are often proteins, but in non-protein coding genes such as ribosomal RNA , transfer RNA or small nuclear RNA genes, the product is a functional RNA...
. Three genes were measured in an experiment with Drosophila melanogaster: bicoid (bcd), slalom (sll), and chitin synthase (cs). These three genes were used because they are likely to be in varied levels during different times of the egg development process. These genes all share a linear relationship in regards to age of the egg; that is, the older the egg is the more of the particular gene is expressed. However, all of the genes are expressed in varying amounts. Different genes on different loci would need to be selected for another fly species. The genes expressions are mapped in a control sample to formulate a developmental chart of the gene expression at certain time intervals. This chart can then be compared to the measured values of gene expression to accurately predict the age of an egg to within two hours with a high confidence level
Confidence interval
In statistics, a confidence interval is a particular kind of interval estimate of a population parameter and is used to indicate the reliability of an estimate. It is an observed interval , in principle different from sample to sample, that frequently includes the parameter of interest, if the...
. Even though this technique can be used to estimate the age of an egg, the feasibility and legal acceptance of this must be considered for it to be a widely utilized forensic technique. One benefit of this would be that it is like other DNA-based techniques so most labs would be equipped to conduct similar experiments without requiring new capital investment. This style of age determination is in the process of being used to more accurately find the age of the instars and pupa; however, it is much more complicated, as there are more genes being expressed during these stages. The hope is that with this and other similar techniques a more accurate PMI can be obtained.
Insect activity case study
A preliminary investigation of insect colonization and succession on remains in New ZealandNew Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
revealed the following results on decay and insect colonization.
Open field habitat
This environment had a daily average maximum temperature of 19.4 °C (66.9 °F) and a daily minimum temperature of 11.1 °C (52 °F). The average rainfall for the first 3 weeks in this environment was 3.0 mm/day. Around days 17–45, the body began to start active decay. During this stage, the insect successions started with CalliphoraCalliphora
Calliphora is the type genus of blow flies, the family Calliphoridae.-Species in the genus Calliphora:...
stygia, which lasted until day 27. The larvae of Chrysomya rufifacies
Chrysomya rufifacies
Chrysomya rufifacies is a species belonging to the blow fly family, Calliphoridae, and is most significant in the field of forensic entomology due to its use in establishing or altering postmortem intervals. The common name for the species is the hairy maggot blow fly, and it belongs to the genus...
were present between the day 13 and day 47. The H. rostrata, larvae of Lucilia sericata, Psychodidae
Psychodidae
The nematoceran family Psychodidae are small true flies with short, hairy bodies and wings giving them a "furry" moth-like appearance...
family, and sylvicola were found to occur relatively late in the body's decay.
Coastal sand-dune habitat
This environment had an average daily maximum temperature of 21.4 °C (70.5 °F) and minimum of 13.5 °C (56.3 °F). The daily average rainfall was recorded as 1.4 mm/day for the first 3 weeks. The post-decay time interval, beginning at day six after death and ending around day 15 after death, is greatly reduced from the average post-decay time, due to the high average temperature of this environment. Insects obtained late in the post-active stage include the Calliphora quadrimaculata, adult Phaeroceridae, PsychodidaePsychodidae
The nematoceran family Psychodidae are small true flies with short, hairy bodies and wings giving them a "furry" moth-like appearance...
and Piophilidae (no larvae from this family were obtained in recovery).
Native bush habitat
This environment had recorded daily average maximum and minimum temperatures were 18 °C (64.4 °F) and 13 °C (55.4 °F), respectively. The average rainfall in this habitat was recorded at 0.4 mm/day. After the bloat stage, which lasted until day seven after death, post-active decay began around day 14. In this habitat, the H. rostrata, Phoridae adult, Sylvicola larvae and adult are the predominant species remaining on the body during the pre-skeletonizationSkeletonization (forensics)
In forensics, skeletonization refers to the complete decomposition of the non-bony tissues of a corpse, leading to a bare skeleton. In a temperate climate, it usually requires three weeks to several years for a body to completely decompose into a skeleton, depending on factors such as temperature,...
stages.
In literature
Throughout its history the study of forensic entomology has not remained an esoteric science reserved only for entomologists and forensic scientists.Early twentieth-century popular scientific literature began to pique a broader interest in entomology
Entomology
Entomology is the scientific study of insects, a branch of arthropodology...
. The very popular ten-volume book series, Alfred Brehem’s Thierleben (Life of Animals, 1876–1879) expounded on many zoological topics, including arthropods. The accessible writing style of French entomologist Jean-Henri Fabre was also instrumental in the popularization of entomology. His collection of writings Souvenirs Entomologique, written during the last half of the 19th century, is especially useful because of the meticulous attention to detail to the observed insects’ behaviors and life cycles.
The real impetus behind the modern cultural fascination with solving crime using entomological evidence can be traced back to the works Faune de Tombeaux (Fauna of the Tomb, 1887) and Les Faunes des Cadavres (Fauna of the Cadaver, 1894) by French veterinarian
Veterinarian
A veterinary physician, colloquially called a vet, shortened from veterinarian or veterinary surgeon , is a professional who treats disease, disorder and injury in animals....
and entomologist Jean Pierre Mégnin
Jean Pierre Mégnin
Jean Pierre Mégnin was a French army veterinarian and entomologist. He is best known for his work with dogs and forensic entomology....
. These works made the concept of the process of insect ecological succession on a corpse understandable and interesting to an ordinary reader in a way that no other previous scientific work had done. It was after the publication of Mégnin’s work that the studies of forensic science and entomology became an established part of Western popular culture, which in turn inspired other scientists to continue and expand upon his research.
See also
- Forensic entomologistForensic entomologistForensic entomologists are those involved in the branch of entomology that involves insects and violent crime or the law, known as forensic entomology. This includes three main branches: medicocriminal entomology, urban entomology, and stored product entomology...
- Forensic entomology and the lawForensic entomology and the lawForensic entomology deals with the collection of arthropodic evidence and its application, and through a series of tests and previously set of rules, general admissibility of said evidence is determined. Ultimately, the admissibility of forensic evidence is left up to the judgement of the court...
- Insect indicators of abuse or neglectInsect indicators of abuse or neglectEntomological evidence is legal evidence in the form of insects or related artifacts and is a field of study in forensic entomology. Such evidence is used particularly in medicolegal and medicocriminal applications. Insect evidence is customarily used to determine post mortem interval , but can...
- Mark BeneckeMark BeneckeMark Benecke is a German forensic biologist.Benecke was born in Rosenheim . After receiving a Dr. rer. medic. at Cologne University in 1997, he worked in the Chief Medical Examiner's Office in Manhattan, New York from 1997–1999. , he works internationally on forensic cases as a freelance expert...
, noted forensic entomologist
Further reading
Spiralbound also aimed at professional entomologists, but shorter and with a popular style. A technical hardback designed for professional entomologists.External links
- www.forensic-entomology.com by Dr. Jason H. Byrd
- European Association for Forensic Entomology homepage
- Collection of original articles about Forensic Entomology. Many downloadable illustrated pdf's of cases
- Institute of Forensic Entomology Vienna Click on the pictures for enlargements and graphs
- What happens to the body after death
- Pastoral putrefaction down on the Body Farm: Autopsy, HBO Documentaries
- Dating Death Great Moments of Science
- DNA techniques for forensic entomology
- pdf about forensic entomology Deon Canyon
- Forensic Entomology page from Australia (Ian Dadour)
- Visible Proofs
- Medical Zoology Pages
- Survey on carrion-visiting beetles – Research into the fauna of carrion-visiting beetles in Erlangen, Bavaria (2006): Carrion is an ecosystem of its own. Diverse species of beetles – belonging to different guilds – arrive and depart from carrion at different times – succession occurs. The arrival time and growth rates of beetles inhabiting corpses depending on weather, location and type of carrion have been studied.
- Forensic Entomology the next step (ForensicWiki)
- Diagnosis and Keys to South American Coleoptera of Forensic Importance
- Forensic entomology - use of insects to help solve crime
- A Forensic Entomology Case from the Amazon Rain Forest of Brazil
- Run models and calculate degree-days
- Growing Degree Days
- Grounds Maintenance magazine