Tobacco hornworm
Encyclopedia
Manduca sexta is a moth
of the family Sphingidae
present through much of the American
continent. Commonly known as the tobacco hornworm, it is closely related to and often confused with the very similar tomato hornworm
(Manduca quinquemaculata); the larva
e of both feed on the foliage of various plants from the family Solanaceae
. The tobacco hornworm can be distinguished by its seven diagonal lines on its sides; tomato hornworms have eight V-shaped markings. A mnemonic to remember the markings is tobacco hornworms have straight white lines like cigarettes, while tomato hornworms have V-shaped markings (as in "vine-ripened" tomatoes). M. sexta has mechanisms for selectively sequestering and secreting the neurotoxin
nicotine
present in tobacco.
M. sexta is a common model organism
, especially in neurobiology, due to its easily accessible nervous system
and short life cycle. It is used in a variety of biomedical and biological scientific experiments. It can be easily raised on a wheat-germ based diet. The larva is large and thus relatively easy to dissect and isolate organs.
.
are spherical, approximately 1 millimeter in diameter, and translucent green in color. They typically hatch 2–4 days after they are laid. Eggs are normally found on the underside of foliage, but can also be found on the upper surface.
M. sexta larvae are green in color and grow up to 70 millimeters in length. Under laboratory conditions, while fed a wheat-germ based diet, larvae are turquoise
due to a lack of pigments in their diet. M. sexta blood contains the blue-colored protein insecticyanin. When the larva feeds on plants it ingests pigment
acious carotenoid
proteins. Carotenoids are primarily yellow in hue. When bound together, the protein complex is green.
During the larva
l stage, M. sexta caterpillars feed on plants of the family Solanaceae
, principally tobacco
, tomatoes and members of the Datura
genus. Near the end of this stage, the caterpillar seeks a location for pupa
tion, burrows underground, and pupates. The searching behaviour is known as "wandering." The instinct of wandering can be visually confirmed by spotting the heart (aorta) which is a long, pulsating vein running along the length of the caterpillar's dorsal side. The heart appears just as the caterpillar is reaching the end of the final instar. M. sexta has five larval instar
s which are separated by ecdysis
(molting), but may add larval instars when nutrient conditions are poor.
A common biological control
for hornworms is the parasitic
braconid wasp
, Cotesia
, which lays its eggs in the bodies of tobacco hornworms. The wasp larvae feed internally, and emerge from the body to spin their cocoons. Parasitized tobacco hornworms are often seen covered with multiple white, cotton
y wasp cocoons, which are often mistaken for large eggs.
Before the larva pupates, it goes through a stage called the pre-pupa, where its shrinks considerably and prepares to pupate. Often, people mistake this stage as a dead, or dying, caterpillar.
Adult males and females are sexually dimorphic
. Males are identifiable by their broader antennae
and the presence of claspers
at the end of the abdomen
. Female moths are typically ready to mate one week after eclosion, and do so only once. Males may mate many times. Mating generally occurs on a vertical surface at night, and can last several hours, with the male and female facing in opposite positions, their posterior ends touching. After mating, females deposit their fertilized eggs on foliage, usually on the underside of leaves.
, Manduca sexta is commonly used as a model organism
for experiments. M. sexta are frequently studied in the laboratory due to their large size and relative ease of rearing. They may be reared on host plants, such as tobacco and tobacco relatives, tomato plants, or wheat germ based artificial diet. Their rearing is straightforward, as long as they receive a "long day" (i.e., 14 hour) daylight cycle during development to prevent diapause
.
Eggs are rinsed for one to five minutes in diluted household bleach, at Binghamton University
.05% Clorox
is used.
Eggs are placed on diet cubes or host plants. The eggs hatch and develop at different speeds depending on temperature. The Manduca are moved to fresh diet or leaves as their food spoils or is consumed. When the Manduca "wanders" (non-stop walking) it is about to pupate and is placed in a pupation chamber. Pupation chambers are holes drilled into a wood board. The Manduca larvae is sealed in the chamber using a stopper, and allowed to pupate. After pupation the pupae is placed in a breeding or colony chamber to eclose
. Providing a cup of sugar water and a tobacco (or related plant) will allow mated females to oviposit fertile eggs, which can then be reared.
When fed an artificial diet Manduca larvae do not consume the Xanthophyll
needed to produce their green coloration, instead they appear blue. On some diets the Manduca have very little pigment and pigment precursors, so the Manduca larvae are a very pale blue-white. As vitamin A and other carotenoids are necessary for the visual pigments (rhodopsin
,) it is worth noting that an artificial diet-reared manduca may have poor vision due to lack of carotenoids in the diet.
Moth
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...
of the family Sphingidae
Sphingidae
Sphingidae is a family of moths , commonly known as hawk moths, sphinx moths and hornworms, that includes about 1,200 species . It is best represented in the tropics but there are species in every region . They are moderate to large in size and are distinguished among moths for their rapid,...
present through much of the American
Americas
The Americas, or America , are lands in the Western hemisphere, also known as the New World. In English, the plural form the Americas is often used to refer to the landmasses of North America and South America with their associated islands and regions, while the singular form America is primarily...
continent. Commonly known as the tobacco hornworm, it is closely related to and often confused with the very similar tomato hornworm
Tomato hornworm
The Five-Spotted Hawkmoth is a brown and gray hawk moth of the Sphingidae family. The caterpillar is often referred to as the tomato hornworm and can be a major pest in gardens. Tomato hornworms are closely related to the tobacco hornworm...
(Manduca quinquemaculata); the 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 of both feed on the foliage of various plants from the family Solanaceae
Solanaceae
Solanaceae are a family of flowering plants that include a number of important agricultural crops as well as many toxic plants. The name of the family comes from the Latin Solanum "the nightshade plant", but the further etymology of that word is unclear...
. The tobacco hornworm can be distinguished by its seven diagonal lines on its sides; tomato hornworms have eight V-shaped markings. A mnemonic to remember the markings is tobacco hornworms have straight white lines like cigarettes, while tomato hornworms have V-shaped markings (as in "vine-ripened" tomatoes). M. sexta has mechanisms for selectively sequestering and secreting the neurotoxin
Neurotoxin
A neurotoxin is a toxin that acts specifically on nerve cells , usually by interacting with membrane proteins such as ion channels. Some sources are more general, and define the effect of neurotoxins as occurring at nerve tissue...
nicotine
Nicotine
Nicotine is an alkaloid found in the nightshade family of plants that constitutes approximately 0.6–3.0% of the dry weight of tobacco, with biosynthesis taking place in the roots and accumulation occurring in the leaves...
present in tobacco.
M. sexta is a common model organism
Model organism
A model organism is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the organism model will provide insight into the workings of other organisms. Model organisms are in vivo models and are widely used to...
, especially in neurobiology, due to its easily accessible nervous system
Nervous system
The nervous system is an organ system containing a network of specialized cells called neurons that coordinate the actions of an animal and transmit signals between different parts of its body. In most animals the nervous system consists of two parts, central and peripheral. The central nervous...
and short life cycle. It is used in a variety of biomedical and biological scientific experiments. It can be easily raised on a wheat-germ based diet. The larva is large and thus relatively easy to dissect and isolate organs.
Subspecies
- Manduca sexta sexta (from Massachusetts west across southern Michigan to Minnesota, central Colorado, and northern California, south to Florida, the Gulf Coast, Texas, New Mexico, Arizona, and southern California and then further south through Mexico, Belize, Honduras, Nicaragua, Costa Rica, and the West Indies to Argentina)
- Manduca sexta caestri (Blanchard, 1854) (Chile)
- Manduca sexta jamaicensis (Butler, 1875) (Jamaica, the Dominican Republic, St. Lucia, Guadeloupe and throughout the Antilles)
- Manduca sexta leucoptera (Rothschild & Jordan, 1903) (Galapagos Islands)
- Manduca sexta paphus (Cramer, 1779) (Surinam and Venezuela to Brazil, Argentina and Bolivia)
- Manduca sexta saliensis (Kernbach, 1964) (Argentina)
Life cycle
M. sexta have a short life cycle, lasting about 30 to 50 days. In most areas, M. sexta have about two generations per year, but they can have about three or four generations per year in FloridaFlorida
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...
.
Eggs
M. sexta 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...
are spherical, approximately 1 millimeter in diameter, and translucent green in color. They typically hatch 2–4 days after they are laid. Eggs are normally found on the underside of foliage, but can also be found on the upper surface.
Larvae
Turquoise (color)
Turquoise or is a slightly blueish tone of light green. The color is based on the gem turquoise. The term comes from the French for Turkish.At right is displayed the X11 color named turquoise....
due to a lack of pigments in their diet. M. sexta blood contains the blue-colored protein insecticyanin. When the larva feeds on plants it ingests pigment
Pigment
A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light.Many materials selectively absorb...
acious carotenoid
Carotenoid
Carotenoids are tetraterpenoid organic pigments that are naturally occurring in the chloroplasts and chromoplasts of plants and some other photosynthetic organisms like algae, some bacteria, and some types of fungus. Carotenoids can be synthesized fats and other basic organic metabolic building...
proteins. Carotenoids are primarily yellow in hue. When bound together, the protein complex is green.
During the 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...
l stage, M. sexta caterpillars feed on plants of the family Solanaceae
Solanaceae
Solanaceae are a family of flowering plants that include a number of important agricultural crops as well as many toxic plants. The name of the family comes from the Latin Solanum "the nightshade plant", but the further etymology of that word is unclear...
, principally tobacco
Tobacco
Tobacco is an agricultural product processed from the leaves of plants in the genus Nicotiana. It can be consumed, used as a pesticide and, in the form of nicotine tartrate, used in some medicines...
, tomatoes and members of the Datura
Datura
Datura is a genus of nine species of vespertine flowering plants belonging to the family Solanaceae. Its precise and natural distribution is uncertain, owing to its extensive cultivation and naturalization throughout the temperate and tropical regions of the globe...
genus. Near the end of this stage, the caterpillar seeks a location for 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...
tion, burrows underground, and pupates. The searching behaviour is known as "wandering." The instinct of wandering can be visually confirmed by spotting the heart (aorta) which is a long, pulsating vein running along the length of the caterpillar's dorsal side. The heart appears just as the caterpillar is reaching the end of the final instar. M. sexta has five larval instar
Instar
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...
s which are separated by ecdysis
Ecdysis
Ecdysis is the moulting of the cuticula in many invertebrates. This process of moulting is the defining feature of the clade Ecdysozoa, comprising the arthropods, nematodes, velvet worms, horsehair worms, rotifers, tardigrades and Cephalorhyncha...
(molting), but may add larval instars when nutrient conditions are poor.
A common biological control
Biological pest control
Biological control of pests in agriculture is a method of controlling pests that relies on predation, parasitism, herbivory, or other natural mechanisms...
for hornworms is the parasitic
Parasitism
Parasitism is a type of symbiotic relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host. Traditionally parasite referred to organisms with lifestages that needed more than one host . These are now called macroparasites...
braconid wasp
Braconidae
Braconidae is a family of parasitoid wasps and one of the richest families of insects. Between 50,000 and 150,000 species exist worldwide. The species are grouped into about 45 subfamilies and 1,000 genera, some important ones being: Ademon, Aphanta, Asobara, Bracon hebetor, Cenocoelius, Chaenusa,...
, Cotesia
Cotesia congregata
Cotesia congregata is a parasitic wasp of the genus Cotesia.-Life cycle:Adult wasps lay their eggs in tobacco hornworm larvae and at the same time injects symbiotic viruses into the hemocoel of the host...
, which lays its eggs in the bodies of tobacco hornworms. The wasp larvae feed internally, and emerge from the body to spin their cocoons. Parasitized tobacco hornworms are often seen covered with multiple white, cotton
Cotton
Cotton is a soft, fluffy staple fiber that grows in a boll, or protective capsule, around the seeds of cotton plants of the genus Gossypium. The fiber is almost pure cellulose. The botanical purpose of cotton fiber is to aid in seed dispersal....
y wasp cocoons, which are often mistaken for large eggs.
Pre-pupae
Pupae
The pupal stage lasts approximately 18 days under laboratory conditions (17 hours light, 7 hours dark, 27°C). When reared on a short-day photoperiod (12 hours light, 12 hours dark), pupae enter a state of diapause that can last several months. During the pupal stage, structures of the adult moth form within the pupal case which is shed during eclosion (adult emergence).Adults
Adult M. sexta are known as Carolina Sphinx moths. M. sexta moths are nectarivorous and feed on flowers, demonstrating a remarkable ability to hover.Adult males and females are sexually dimorphic
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
. Males are identifiable by their broader antennae
Antenna (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....
and the presence of claspers
Valva
In biology, a clasper is a male anatomical structure found some groups of animals, used in mating.Male cartilaginous fish have claspers formed from the posterior portion of their pelvic fin which serve as intromittent organs used to channel semen into the female's cloaca during mating...
at the end of the 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...
. Female moths are typically ready to mate one week after eclosion, and do so only once. Males may mate many times. Mating generally occurs on a vertical surface at night, and can last several hours, with the male and female facing in opposite positions, their posterior ends touching. After mating, females deposit their fertilized eggs on foliage, usually on the underside of leaves.
Laboratory Rearing
Like drosophila melanogasterDrosophila melanogaster
Drosophila melanogaster is a species of Diptera, or the order of flies, in the family Drosophilidae. The species is known generally as the common fruit fly or vinegar fly. Starting from Charles W...
, Manduca sexta is commonly used as a model organism
Model organism
A model organism is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the organism model will provide insight into the workings of other organisms. Model organisms are in vivo models and are widely used to...
for experiments. M. sexta are frequently studied in the laboratory due to their large size and relative ease of rearing. They may be reared on host plants, such as tobacco and tobacco relatives, tomato plants, or wheat germ based artificial diet. Their rearing is straightforward, as long as they receive a "long day" (i.e., 14 hour) daylight cycle during development to prevent diapause
Diapause
Diapause is the delay in development in response to regularly and recurring periods of adverse environmental conditions. It is considered to be a physiological state of dormancy with very specific initiating and inhibiting conditions...
.
Eggs are rinsed for one to five minutes in diluted household bleach, at Binghamton University
Binghamton University
Binghamton University, also formally called State University of New York at Binghamton, , is a public research university in the State of New York. The University is one of the four university centers in the State University of New York system...
.05% Clorox
Clorox
The Clorox Company is a US-based manufacturer of various food and chemical products based in Oakland, California, which is best known for its bleach product, Clorox.- History :...
is used.
Eggs are placed on diet cubes or host plants. The eggs hatch and develop at different speeds depending on temperature. The Manduca are moved to fresh diet or leaves as their food spoils or is consumed. When the Manduca "wanders" (non-stop walking) it is about to pupate and is placed in a pupation chamber. Pupation chambers are holes drilled into a wood board. The Manduca larvae is sealed in the chamber using a stopper, and allowed to pupate. After pupation the pupae is placed in a breeding or colony chamber to eclose
Eclose
Eclose is a commune in the Isère department in south-eastern France....
. Providing a cup of sugar water and a tobacco (or related plant) will allow mated females to oviposit fertile eggs, which can then be reared.
When fed an artificial diet Manduca larvae do not consume the Xanthophyll
Xanthophyll
Xanthophylls are yellow pigments that form one of two major divisions of the carotenoid group. The name is from Greek xanthos + phyllon , due to their formation of the yellow band seen in early chromatography of leaf pigments...
needed to produce their green coloration, instead they appear blue. On some diets the Manduca have very little pigment and pigment precursors, so the Manduca larvae are a very pale blue-white. As vitamin A and other carotenoids are necessary for the visual pigments (rhodopsin
Rhodopsin
Rhodopsin, also known as visual purple, is a biological pigment of the retina that is responsible for both the formation of the photoreceptor cells and the first events in the perception of light. Rhodopsins belong to the G-protein coupled receptor family and are extremely sensitive to light,...
,) it is worth noting that an artificial diet-reared manduca may have poor vision due to lack of carotenoids in the diet.
External links
- Hornworm description at Colorado State
- Nuisance Parasitic Wasps at Ohio State University Extension
- Butterflies and Moths of North America
- tobacco hornworm on the UFUniversity of FloridaThe University of Florida is an American public land-grant, sea-grant, and space-grant research university located on a campus in Gainesville, Florida. The university traces its historical origins to 1853, and has operated continuously on its present Gainesville campus since September 1906...
/ IFASInstitute of Food and Agricultural SciencesThe University of Florida’s Institute of Food and Agricultural Sciences is a federal-state-county partnership dedicated to developing knowledge in agriculture, human and natural resources, and the life sciences, and enhancing and sustaining the quality of human life by making that information...
Featured Creatures Web site - Manduca sexta Poster illustrating anatomical structures of the head and body