Chrysomya megacephala
Encyclopedia
Chrysomya megacephala, more commonly known as the oriental latrine fly, is a warm-weather fly
with a greenish-blue metallic box-like body which belongs to the family Calliphoridae (blowflies). This fly can be a nuisance to humans and even cause accidental myiasis
. C. megacephala contributes to the evolution of some insects, influences animal atmospheres, negatively alters human public health, and is a tool in forensic entomology
.
and the Australasian region, including the eastern coast of Queensland
and New South Wales
. It is found in Japan
and Palearctic regions as well. Since the 1970s, C. megacephala has extended to different areas of the world, encroaching on the new territories of New Zealand
and Africa
along with South
, Central
, and North America
. C. megacephala began occupying the United States by means of harbors and airports. The oriental latrine fly has been found in California as well as Texas, Louisiana, and Hawaii. C. megacephala consists of two forms, the normal and the derived. Tropical forests on the South Pacific islands
, like Samoa
, are home to the normal form; furthermore, normal is considered the plesiomorphic form of C. megacephala. The derived form is thought to have emerged from Papua New Guinea
and is said to be synanthropic
, ecologically associated with humans.
, the warmer the temperature the longer the fecundity
seems to be the correlation. In large densities of larva, where there are a lot of them in one small area competing for the same food source, the fecundity of the population is less. Where there is more food, there are larger adults and a bigger fecundity. A correlation between wing size and temperature and tibia size and temperature has been found in this species. As temperature increases then wing and tibia size increases. There was a similar relationship between wing and tibia size with fecundity. All three of these values, fecundity, wing size and tibia size are found to stay within the same range throughout the year, so a seasonal correlation seems to be absent. These laboratory findings are true of this species in a tropical environment, namely Brazil
. Researchers have found this surprising since this fly is in high numbers in warm weather and low numbers in cold weather. They thought that the flies would be smaller during the warmer months because of other life tables constructed with other Dipteran species. The majority of Dipteran species that have had a life table constructed have demonstrated a tendency for smaller bodies in the warmer months. It has also been found that C. megacephala has a long lifespan as an adult and this, in part, has helped this species become so successful at invading so many geographical areas. The long lifespan of the adult allows the young to reach adulthood. The parents are there for the entire rearing of the offspring, ensuring survival.
, larva
e, and pupa
stages. When a female fly lays eggs there might be as much as 200 to 300 eggs total. The larva stage includes a first, second, and third instar, or growth period within the larva stage. C. megacephala eggs take approximately 100 days to develop while the larva will take 86 days and pupa 85 days. Population numbers as well as body size are greatly influenced by temperature. After completing all developmental stages, the C. megacephala life cycle consists of approximately 7 days. Since C. megacephala has become forensically important, knowledge of development rates for these blowflies has become a necessity. C. megacephala development appears to be linked with the surrounding temperature and the length of time spent feeding in the larval stage. Development rate is mainly dependent on temperature, lower the temperature and larvae develop slower; raise the temperature and the larvae will develop faster. Most studies conducted on developmental rate are done at 27°C. At this temperature eggs hatch-18 hrs, 1st molt-30hrs, 2nd molt-72hrs, pupation-144hrs, adult emerges-234hrs. It is also noted that these times can vary depending on geographical locations and other environmental factors can determine how long flies will stay in the larvae stage. Males tend to emerge only 2–3 hrs ahead of the females.
and abdomen
and have very large red eyes on a large head. They have yellow gena, or cheeks. Larvae vary in size according to which instar it exists in at any given time. Larvae shape is thicker towards the rear side and thins out near the head. With all the problems that C. megacephala create, this group is one that needs to be
recognized. C. megacephala are identified as having large red eyes with the males being close together and the females farther apart. Also, the cercus of the male is longer than that of the female.
is mainly used to determine subfamilies of Chrysomyinae. Its wide geographical distribution and high fecundity
allow it to be used in many forensic cases around the world. These cases are studied as a whole to find trends in insects collected off the bodies and from these studies it has been concretely concluded that C. megacephala is one of the most common blowflies found. The larval dispersion patterns of C. megacephala also make it a forensically important fly. To pupate, the larva move away from the food source to find a safe place to metamorphose. It is an important aspect for forensic entomologists to know so that they can accurately calculate a post mortem interval
. Knowing to look under the body and in adjacent areas can be vital information for any case.
was used to compare and note what species of insects they found on 30 cases of cadavers. These 30 bodies were grouped into the specific environment they were found in urban-outdoor, urban-indoor, and forested area. C. megacephala was the most common fly found on these bodies, found on 20 bodies out of the 30 total. Calliphoridae was, by far, the most common family of flies found on all of these cadavers. Chrysomya megacephala was also found in more forested areas than C. rufifacies.
often engenders death, and in many cases, by evaluating the body tissue and fluids, the toxin can be identified as the source of the poisoning. However, it is somewhat difficult to evaluate the body tissue in a body that is exceedingly decomposed. Nevertheless, a medical examiner in Hawaii worked a case in which malathion
poisoning, an organophosphate insecticide, was thought to be the cause death. The victim’s stomach content and body fat were examined and found to have contained malathion. The fly larvae of Chrysomya megacephala and Chrysomya rufifacies
were also present at the scene on the body and were tested for malathion. Both of these species did contain malathion, but there had been no previous record of organophosphate in larvae. Studying larvae from decomposed remains may provide an effective method in determining these toxins on a body that is extremely decayed.
for mango in the Australian region. While most areas wish to rid themselves of C. megacephala, Taiwan farmers have found ways in which to enhance the population of this blowfly so that more mangos will be pollinated.
accumulated within a tumor lesion in male’s right lower leg; however, of the myiasis
cases that are recorded, most do not involve C. megacephala and C. rufifacies. C. megacephala like filth and even lays its eggs on human feces, and after landing on the feces they will land on human food.; this is how C. megacephala spreads disease, and it is a carrier of pathogens, such as bacteria, protozoan cysts, and helminth eggs, to human food. Not only is this group a huge nuisance, it causes a huge economic problem in Asia, Africa, and the Pacific. In these areas sun-drying fish is a preservation method for sending the fish form where they are caught to the location of markets and consumers. Ice can be used to preserve the fish as well but, these areas are underdeveloped and often cannot afford this method. However, blowfly larvae tend to infect these sun-dried fish when the weather is warm and humid. An experiment was done to observe which flies show up around these sun-dried fish the most, and 95% were C. megacephala. One technique to control this group is using an odor that the flies are attracted to, and then the flies can be trapped. Also, insecticides can be used to handle the problem of Chrysomya megacephala, but sometimes resistance is built up to this control mechanism
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...
with a greenish-blue metallic box-like body which belongs to the family Calliphoridae (blowflies). This fly can be a nuisance to humans and even cause accidental myiasis
Myiasis
Myiasis is a general term for infection by parasitic fly larvae feeding on the host's necrotic or living tissue. Colloquialisms for myiasis include flystrike, blowfly strike, and fly-blown. In Greek, "myia" means fly....
. C. megacephala contributes to the evolution of some insects, influences animal atmospheres, negatively alters human public health, and is a tool in forensic entomology
Forensic entomology
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...
.
Regions and areas found
C. megacephala stretches across vast regions of the world. It is particularly prevalent in the Oriental regionOrient
The Orient means "the East." It is a traditional designation for anything that belongs to the Eastern world or the Far East, in relation to Europe. In English it is a metonym that means various parts of Asia.- Derivation :...
and the Australasian region, including the eastern coast of Queensland
Queensland
Queensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...
and New South Wales
New South Wales
New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...
. It is found in Japan
Japan
Japan 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...
and Palearctic regions as well. Since the 1970s, C. megacephala has extended to different areas of the world, encroaching on the new territories of New Zealand
New 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...
and Africa
Africa
Africa 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...
along with South
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
, Central
Central America
Central 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 North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
. C. megacephala began occupying the United States by means of harbors and airports. The oriental latrine fly has been found in California as well as Texas, Louisiana, and Hawaii. C. megacephala consists of two forms, the normal and the derived. Tropical forests on the South Pacific islands
Pacific Islands
The Pacific Islands comprise 20,000 to 30,000 islands in the Pacific Ocean. The islands are also sometimes collectively called Oceania, although Oceania is sometimes defined as also including Australasia and the Malay Archipelago....
, like Samoa
Samoa
Samoa , officially the Independent State of Samoa, formerly known as Western Samoa is a country encompassing the western part of the Samoan Islands in the South Pacific Ocean. It became independent from New Zealand in 1962. The two main islands of Samoa are Upolu and one of the biggest islands in...
, are home to the normal form; furthermore, normal is considered the plesiomorphic form of C. megacephala. The derived form is thought to have emerged from Papua New Guinea
Papua New Guinea
Papua New Guinea , officially the Independent State of Papua New Guinea, is a country in Oceania, occupying the eastern half of the island of New Guinea and numerous offshore islands...
and is said to be synanthropic
Synanthrope
Synanthropes is a term applied to species of wild animals and plants of various kinds that live near, and benefit from, an association with humans and the somewhat artificial habitats that humans create around them . Those habitats include houses, gardens, farms, roadsides, garbage dumps, and so on...
, ecologically associated with humans.
Ecology
C. megacephala prefers to live in climates that are warm most of the year. It has a long lifespan for a DipteranFly
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...
, the warmer the temperature the longer the fecundity
Fecundity
Fecundity, derived from the word fecund, generally refers to the ability to reproduce. In demography, fecundity is the potential reproductive capacity of an individual or population. In biology, the definition is more equivalent to fertility, or the actual reproductive rate of an organism or...
seems to be the correlation. In large densities of larva, where there are a lot of them in one small area competing for the same food source, the fecundity of the population is less. Where there is more food, there are larger adults and a bigger fecundity. A correlation between wing size and temperature and tibia size and temperature has been found in this species. As temperature increases then wing and tibia size increases. There was a similar relationship between wing and tibia size with fecundity. All three of these values, fecundity, wing size and tibia size are found to stay within the same range throughout the year, so a seasonal correlation seems to be absent. These laboratory findings are true of this species in a tropical environment, namely Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
. Researchers have found this surprising since this fly is in high numbers in warm weather and low numbers in cold weather. They thought that the flies would be smaller during the warmer months because of other life tables constructed with other Dipteran species. The majority of Dipteran species that have had a life table constructed have demonstrated a tendency for smaller bodies in the warmer months. It has also been found that C. megacephala has a long lifespan as an adult and this, in part, has helped this species become so successful at invading so many geographical areas. The long lifespan of the adult allows the young to reach adulthood. The parents are there for the entire rearing of the offspring, ensuring survival.
Development
This fly species is known to breed in human feces, meat, and fish. The developmental stages include eggEgg (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...
, larva
Larva
A 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, and pupa
Pupa
A 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...
stages. When a female fly lays eggs there might be as much as 200 to 300 eggs total. The larva stage includes a first, second, and third instar, or growth period within the larva stage. C. megacephala eggs take approximately 100 days to develop while the larva will take 86 days and pupa 85 days. Population numbers as well as body size are greatly influenced by temperature. After completing all developmental stages, the C. megacephala life cycle consists of approximately 7 days. Since C. megacephala has become forensically important, knowledge of development rates for these blowflies has become a necessity. C. megacephala development appears to be linked with the surrounding temperature and the length of time spent feeding in the larval stage. Development rate is mainly dependent on temperature, lower the temperature and larvae develop slower; raise the temperature and the larvae will develop faster. Most studies conducted on developmental rate are done at 27°C. At this temperature eggs hatch-18 hrs, 1st molt-30hrs, 2nd molt-72hrs, pupation-144hrs, adult emerges-234hrs. It is also noted that these times can vary depending on geographical locations and other environmental factors can determine how long flies will stay in the larvae stage. Males tend to emerge only 2–3 hrs ahead of the females.
Reproduction and survival rates
The factors involved in reproduction and survival rates of C. megacephala are closely related to the developmental factors. The amount of food is important in determining their survival and reproduction. Also, competition from other larvae species, such as C. rufifacies, is another factor in reproduction and survival. When competing larvae are present, the amount of time spent feeding is shortened which leads to early pupation and smaller adults. This will then hasten the reproduction of C. megacephala. C. rufifacies is known to cannibalize maggot masses and thus a huge competitor.Appearance
C. megacephala’s appearance helps to determine the age of the species as well as to distinguish it from other species. Eggs are "oval with one flat face and another convex". Adult flies reflect a metallic blue-green color on their thoraxThorax
The thorax is a division of an animal's body that lies between the head and the abdomen.-In tetrapods:...
and abdomen
Abdomen
In 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...
and have very large red eyes on a large head. They have yellow gena, or cheeks. Larvae vary in size according to which instar it exists in at any given time. Larvae shape is thicker towards the rear side and thins out near the head. With all the problems that C. megacephala create, this group is one that needs to be
recognized. C. megacephala are identified as having large red eyes with the males being close together and the females farther apart. Also, the cercus of the male is longer than that of the female.
Importance in forensic science
C. megacephala is considered one of the most important species of flies to forensic science. This is because it is one of the first species to show up on a corpse. A post mortem interval can be easily calculated when Chrysomya megacephala larva are found on a body because of their abundance. Most forensic entomology cases either have C. rufifacies or Chrysomya megacephala found on the decaying corpse in many areas of the world, and 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...
is mainly used to determine subfamilies of Chrysomyinae. Its wide geographical distribution and high fecundity
Fecundity
Fecundity, derived from the word fecund, generally refers to the ability to reproduce. In demography, fecundity is the potential reproductive capacity of an individual or population. In biology, the definition is more equivalent to fertility, or the actual reproductive rate of an organism or...
allow it to be used in many forensic cases around the world. These cases are studied as a whole to find trends in insects collected off the bodies and from these studies it has been concretely concluded that C. megacephala is one of the most common blowflies found. The larval dispersion patterns of C. megacephala also make it a forensically important fly. To pupate, the larva move away from the food source to find a safe place to metamorphose. It is an important aspect for forensic entomologists to know so that they can accurately calculate 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....
. Knowing to look under the body and in adjacent areas can be vital information for any case.
Specific case studies
One study done in ThailandThailand
Thailand , officially the Kingdom of Thailand , formerly known as Siam , is a country located at the centre of the Indochina peninsula and Southeast Asia. It is bordered to the north by Burma and Laos, to the east by Laos and Cambodia, to the south by the Gulf of Thailand and Malaysia, and to the...
was used to compare and note what species of insects they found on 30 cases of cadavers. These 30 bodies were grouped into the specific environment they were found in urban-outdoor, urban-indoor, and forested area. C. megacephala was the most common fly found on these bodies, found on 20 bodies out of the 30 total. Calliphoridae was, by far, the most common family of flies found on all of these cadavers. Chrysomya megacephala was also found in more forested areas than C. rufifacies.
Larval-state poisoning detection
In any part of the world that uses organophosphates, C. megacephala could prove to be beneficial. Organophosphate compounds are used in agriculture and are highly toxic. Organophosphate poisoningOrganophosphate poisoning
Organophosphate poisoning results from exposure to organophosphates , which cause the inhibition of acetylcholinesterase leading to the accumulation of acetylcholine in the body. Organophosphate poisoning most commonly results from exposure to insecticides or nerve agents...
often engenders death, and in many cases, by evaluating the body tissue and fluids, the toxin can be identified as the source of the poisoning. However, it is somewhat difficult to evaluate the body tissue in a body that is exceedingly decomposed. Nevertheless, a medical examiner in Hawaii worked a case in which malathion
Malathion
Malathion is an organophosphate parasympathomimetic which binds irreversibly to cholinesterase. Malathion is an insecticide of relatively low human toxicity, however one recent study has shown that children with higher levels of organophosphate pesticide metabolites in their urine are more likely...
poisoning, an organophosphate insecticide, was thought to be the cause death. The victim’s stomach content and body fat were examined and found to have contained malathion. The fly larvae of Chrysomya megacephala and 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 also present at the scene on the body and were tested for malathion. Both of these species did contain malathion, but there had been no previous record of organophosphate in larvae. Studying larvae from decomposed remains may provide an effective method in determining these toxins on a body that is extremely decayed.
Use in research other than forensics
C. megacephala has a beneficial and practical purpose apart from being significant to forensic investigations; this blowfly is the source of pollinationPollination
Pollination is the process by which pollen is transferred in plants, thereby enabling fertilisation and sexual reproduction. Pollen grains transport the male gametes to where the female gamete are contained within the carpel; in gymnosperms the pollen is directly applied to the ovule itself...
for mango in the Australian region. While most areas wish to rid themselves of C. megacephala, Taiwan farmers have found ways in which to enhance the population of this blowfly so that more mangos will be pollinated.
Larval competition
When C. megacephala is found on a body, C. rufifacies is not far behind. C. megacephala larvae are known to compete with C. rufifacies larvae for food in a mixed-species environment. Research has shown that under specific population densities C. rufifacies will facultatively feed on other species of maggots and its own species. When C. rufifacies and C. megacephala larvae are put into cultures separately from one another in high densities, C. megacephala has a higher rate of survival than C. rufifacies. C. rufifacies is known to cannibalize when food resources get low, but despite this apparent advantage it had a lower survival rate than C. megacephala. Both species had a lighter adult weight than normal and pupated earlier. The third instar of C. rufifacies will eat Chrysomya megacephala when the larvae are in high density. Despite predating on Chrysomya megacephala, both species had a lower survival rate, lighter adult weight and pupated early. This is helpful to know in court cases because it could affect the time of death estimation. If there is only C. rufifacies found on a body, it is not accurate to only use this species to calculate a time of colonization. The colonization of C. megacephala prior to C. rufifacies must be taken into account.Predators and prey
Chrysomya albiceps is also known to predate on C. megacephala during the larval stage when they must compete for the same food source. Beetles are also known to predate on C. megacephala. C. megacephala is not predaceous in the adult or larval form, preferring to feed on necrophagous material of any kind such as fish, cows and humans.Agricultural importance
C. megacephala causes myiasis in humans and animals. This causes losses in cattle and fish industries all over the world. Also, studies are being done on C. megacephala to determine its role as a vector for diarrhea-causing bacteria such as E-coli. Actual transmission has not been completely isolated but there are three theories on the way disease/bacteria are transmitted: through the flies’ saliva, feces, or externally.Public health importance and management control
Although this group can aid in pollination, C. megacephala can cause many problems as well. C. megacephala are known to be the source of accidental (secondary) myiasis in humans, meaning that these flies do not pierce the skin but invade an open wound. In Thailand the first record of myiasis was that of a male, 53, where C. megacephala and C. rufifacies in their third instarInstar
An instar is a developmental stage of arthropods, such as insects, between each molt , until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or assume a new form. Differences between instars can often be seen in altered body proportions, colors, patterns, or...
accumulated within a tumor lesion in male’s right lower leg; however, of the myiasis
Myiasis
Myiasis is a general term for infection by parasitic fly larvae feeding on the host's necrotic or living tissue. Colloquialisms for myiasis include flystrike, blowfly strike, and fly-blown. In Greek, "myia" means fly....
cases that are recorded, most do not involve C. megacephala and C. rufifacies. C. megacephala like filth and even lays its eggs on human feces, and after landing on the feces they will land on human food.; this is how C. megacephala spreads disease, and it is a carrier of pathogens, such as bacteria, protozoan cysts, and helminth eggs, to human food. Not only is this group a huge nuisance, it causes a huge economic problem in Asia, Africa, and the Pacific. In these areas sun-drying fish is a preservation method for sending the fish form where they are caught to the location of markets and consumers. Ice can be used to preserve the fish as well but, these areas are underdeveloped and often cannot afford this method. However, blowfly larvae tend to infect these sun-dried fish when the weather is warm and humid. An experiment was done to observe which flies show up around these sun-dried fish the most, and 95% were C. megacephala. One technique to control this group is using an odor that the flies are attracted to, and then the flies can be trapped. Also, insecticides can be used to handle the problem of Chrysomya megacephala, but sometimes resistance is built up to this control mechanism