''Manduca sexta'' is a

moth Moths are a paraphyletic group of insects that includes all members of the order Lepidoptera that are not butterflies, with moths making up the vast majority of the order. There are thought to be approximately 160,000 species of moth, many of w ...

of the family

Sphingidae The Sphingidae are a family of moths (Lepidoptera) called sphinx moths, also colloquially known as hawk moths, with many of their caterpillars known as “hornworms”; it includes about 1,450 species. It is best represented in the tropics, but ...

present through much of the

Americas The Americas, which are sometimes collectively called America, are a landmass comprising the totality of North America, North and South America. The Americas make up most of the land in Earth's Western Hemisphere and comprise the New World. ...

. The species was first described by

Carl Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his ennoblement in 1761 as Carl von Linné Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomial nomenclature, ...

in his 1763 ''

Centuria Insectorum The first page of ''Centuria Insectorum'', as included in ''Amoenitates Academicæ'' ' (Latin, "one hundred insects") is a 1763 taxonomic work by Carl Linnaeus, and defended as a thesis by Boas Johansson; which of the two men should for taxonom ...

''. Commonly known as the Carolina sphinx moth and the tobacco hawk moth (as adults) and the tobacco hornworm and the Goliath worm (as larvae), it is closely related to and often confused with the very similar

tomato hornworm ''Manduca quinquemaculata'', the five-spotted hawkmoth, is a brown and gray hawk moth of the family Sphingidae. The caterpillar, often referred to as the tomato hornworm, can be a major pest in gardens; they get their name from a dark projection ...

(''Manduca quinquemaculata''); the

larva A larva (; plural larvae ) 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 of the family

Solanaceae The Solanaceae , or nightshades, are a family of flowering plants that ranges from annual and perennial herbs to vines, lianas, epiphytes, shrubs, and trees, and includes a number of agricultural crops, medicinal plants, spices, weeds, and or ...

. The tobacco hornworm is sometimes kept as a pet by children throughout its range. The larvae of these species can be distinguished by their lateral markings: Tomato hornworms have eight V-shaped white markings with no borders; tobacco hornworms have seven white diagonal lines with a black border. Additionally, tobacco hornworms have red horns, while tomato hornworms have dark blue or black horns. A

mnemonic A mnemonic ( ) device, or memory device, is any learning technique that aids information retention or retrieval (remembering) in the human memory for better understanding. Mnemonics make use of elaborative encoding, retrieval cues, and image ...

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 Neurotoxins are toxins that are destructive to nerve tissue (causing neurotoxicity). Neurotoxins are an extensive class of exogenous chemical neurological insultsSpencer 2000 that can adversely affect function in both developing and mature nerv ...

nicotine Nicotine is a naturally produced alkaloid in the nightshade family of plants (most predominantly in tobacco and '' Duboisia hopwoodii'') and is widely used recreationally as a stimulant and anxiolytic. As a pharmaceutical drug, it is use ...

present in tobacco. ''M. sexta'' is a common

model organism A model organism (often shortened to model) is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the model organism will provide insight into the workin ...

, especially in

neurobiology Neuroscience is the scientific study of the nervous system (the brain, spinal cord, and peripheral nervous system), its functions and disorders. It is a multidisciplinary science that combines physiology, anatomy, molecular biology, developme ...

, due to its easily accessible

nervous system In biology, the nervous system is the highly complex part of an animal that coordinates its actions and sensory information by transmitting signals to and from different parts of its body. The nervous system detects environmental changes ...

and short life cycle. Doe to its immense size ''M. sexta'' is big enough for medical imaging modalities (like CT, MRI, or

PET A pet, or companion animal, is an animal kept primarily for a person's company or entertainment rather than as a working animal, livestock, or a laboratory animal. Popular pets are often considered to have attractive appearances, intelligence ...

) and used as a model in imaging and gut inflammation. 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 it is relatively easy to dissect it and isolate its organs.

Life cycle

''M. sexta'' has a short life cycle, lasting about 30 to 50 days. In most areas, ''M. sexta'' has about two generations per year, but can have three or four generations per year in Florida.

Eggs

''M. sexta'' eggs are spherical, approximately 1.5 millimeters in diameter, and translucent green. They typically hatch two to four days after they are laid. Eggs are normally found on the underside of foliage, but can also be found on the upper surface.

Larva

''M. sexta'' larvae are bright green in color and grow up to 70 millimeters in length. The posterior

abdominal The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the to ...

segment is tipped with a dorsocaudal horn that earns them the name "hornworm". The final

instar An instar (, from the Latin '' īnstar'', "form", "likeness") is a developmental stage of arthropods, such as insects, between each moult (''ecdysis''), until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or ...

consists of a cylindrical body covered with fine hairlike

seta In biology, setae (singular seta ; from the Latin word for "bristle") are any of a number of different bristle- or hair-like structures on living organisms. Animal setae Protostomes Annelid setae are stiff bristles present on the body. ...

e. The head is equipped with a pair of

ocelli A simple eye (sometimes called a pigment pit) refers to a form of eye or an optical arrangement composed of a single lens and without an elaborate retina such as occurs in most vertebrates. In this sense "simple eye" is distinct from a multi-l ...

and chewing mouthparts. Each of the three

thoracic The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the crea ...

segments bears a pair of true legs, and there is a pair of

proleg A proleg is a small, fleshy, stub structure found on the ventral surface of the abdomen of most larval forms of insects of the order Lepidoptera, though they can also be found on other larval insects such as sawflies and a few other types of in ...

s on the third, fourth, fifth, sixth, and last abdominal segments in all larval instars. The prothoracic segment bears one pair of spiracles, and additional pairs occur on each of the eight abdominal segments. The

hemolymph Hemolymph, or haemolymph, is a fluid, analogous to the blood in vertebrates, that circulates in the interior of the arthropod (invertebrate) body, remaining in direct contact with the animal's tissues. It is composed of a fluid plasma in which ...

(blood) of this species contains insecticyanin, a blue-colored biliprotein. When the larva feeds on its normal diet of plant foliage, it ingests pigmentacious

carotenoid Carotenoids (), also called tetraterpenoids, are yellow, orange, and red organic pigments that are produced by plants and algae, as well as several bacteria, and fungi. Carotenoids give the characteristic color to pumpkins, carrots, parsnips, ...

s, which are primarily yellow in hue. The resulting combination is green. Under laboratory conditions—when fed a wheat-germ-based diet—larvae are turquoise in color due to the lack of carotenoids in their diet. The

caterpillar Caterpillars ( ) are the larval stage of members of the order Lepidoptera (the insect order comprising butterflies and moths). As with most common names, the application of the word is arbitrary, since the larvae of sawflies (suborder Sy ...

stage of the tobacco hornworm is quite similar in appearance to that of the closely-related

. The larvae of these two species can however be readily distinguished by their lateral markings. Specifically, the ''M. sexta'' caterpillar has seven white diagonal lines with a black border at the first seven abdominal segments, and the horn is red or green with a red tip. The ''M. quinquemaculata''caterpillar has V-shaped white markings with no borders at all eight of its abdominal segments, and the horn is dark blue or black in color. During the larval stage, ''M. sexta'' caterpillars feed on plants of the family

, principally tobacco, tomatoes and members of the genus ''

Datura ''Datura'' is a genus of nine species of highly poisonous, vespertine-flowering plants belonging to the nightshade family Solanaceae. They are commonly known as thornapples or jimsonweeds, but are also known as devil's trumpets (not to be co ...

''. ''M. sexta'' has five larval instars, which are separated by

ecdysis Ecdysis is the moulting of the cuticle in many invertebrates of the clade Ecdysozoa. Since the cuticle of these animals typically forms a largely inelastic exoskeleton, it is shed during growth and a new, larger covering is formed. The remnan ...

(molting), but may add larval instars when nutrient conditions are poor. Near the end of this stage, the caterpillar seeks a location for

pupa A pupa ( la, pupa, "doll"; plural: ''pupae'') is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in thei ...

tion, burrows underground, and pupates. This searching behavior is known as "wandering". The imminence of pupation—suggested behaviorally by the wandering—can be anatomically confirmed by spotting the

heart The heart is a muscular Organ (biology), organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as ca ...

(aorta), which is a long, pulsating vessel running along the length of the caterpillar's dorsal side. The heart becomes visible through the skin just as the caterpillar is reaching the end of the final instar. A common

biological control Biological control or biocontrol is a method of controlling pests, such as insects, mites, weeds, and plant diseases, using other organisms. It relies on predation, parasitism, herbivory, or other natural mechanisms, but typically also i ...

for hornworms is the

parasitic Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson ha ...

braconid wasp '' Cotesia congregata'', which lays its eggs in the bodies of the hornworms. The wasp larvae feed internally and emerge from the body to spin their cocoons. Parasitized hornworms are often seen covered with multiple white, cottony wasp cocoons, which are often mistaken for large eggs. A

wasp A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder ...

species, '' Polistes erythrocephalus,'' feeds on hornworm larvae. Tobacco Hornworm 1.jpg Manduca sexta larval stage.jpeg, In the larval state its back end might be confused as its head. Tobacco Hornworm 1 by Max Wahrhaftig.jpg, With parasitic wasp cocoons Manduca Pupae.jpg, Pupa

Pre-pupa

Before the larva pupates, it goes through a stage called the pre-pupa, where it shrinks considerably and prepares to pupate. Often people mistake this stage for a dead or dying caterpillar.

Pupa

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 Photoperiodism is the physiological reaction of organisms to the length of night or a dark period. It occurs in plants and animals. Plant photoperiodism can also be defined as the developmental responses of plants to the relative lengths of light a ...

(12 hours light, 12 hours dark), pupae enter a state of

diapause In animal dormancy, diapause is the delay in development in response to regular and recurring periods of adverse environmental conditions.Tauber, M.J., Tauber, C.A., Masaki, S. (1986) ''Seasonal Adaptations of Insects''. Oxford University Press I ...

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).

Adult

Adult ''M. sexta'' have narrow wings with a wing span of approximately 100 mm. ''M. sexta'' moths are nectarivorous and feed on flowers, demonstrating a remarkable ability to hover. Adults are

sexually dimorphic Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most ani ...

. 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 MHNT CUT 2010 0 104 Caranavi, La Paz Bolivia male dorsal.jpg, Male Manduca sexta MHNT CUT 2010 0 104 Caranavi, La Paz Bolivia male ventral.jpg, Male underside Manduca sexta MHNT CUT 2010 0 104 Dos Amates Catemaco VeraCruz Mexico female dorsal.jpg, Female Manduca sexta MHNT CUT 2010 0 104 Dos Amates Catemaco VeraCruz Mexico female ventral.jpg, Female underside

Laboratory rearing

Like ''

Drosophila melanogaster ''Drosophila melanogaster'' is a species of fly (the taxonomic order Diptera) in the family Drosophilidae. The species is often referred to as the fruit fly or lesser fruit fly, or less commonly the " vinegar fly" or "pomace fly". Starting with ...

'', ''M. sexta'' is commonly used as a

for experiments. They 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, provided they receive a long daylight cycle (e.g., 14 hours) during development to prevent

. Eggs are rinsed for one to five minutes in dilute household bleach for disinfection. Eggs are placed on diet cubes or host plants. The eggs hatch and develop at different speeds depending on temperature. The larvae are moved to a fresh diet or leaves as their food spoils or is consumed. When they start to "wander", they are about to pupate, so are placed in a pupation chamber. Pupation chambers are holes drilled into a wood board. The ''Manduca'' larvae are sealed in the chamber using a stopper and allowed to pupate. After pupation, the pupae are 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 The ovipositor is a tube-like organ used by some animals, especially insects, for the laying of eggs. In insects, an ovipositor consists of a maximum of three pairs of appendages. The details and morphology of the ovipositor vary, but typical ...

fertile eggs, which can then be reared. When fed an artificial diet, ''Manduca'' larvae do not consume the

xanthophyll Xanthophylls (originally phylloxanthins) are yellow pigments that occur widely in nature and form one of two major divisions of the carotenoid group; the other division is formed by the carotenes. The name is from Greek (, "yellow") and (, "lea ...

-which is a yellow pigment- needed to produce their green coloration; instead they appear blue. On some diets, they have very little pigment and pigment precursors, so are a very pale blue-white. As vitamin A and other

s are necessary for the visual pigments (

rhodopsin Rhodopsin, also known as visual purple, is a protein encoded by the RHO gene and a G-protein-coupled receptor (GPCR). It is the opsin of the rod cells in the retina and a light-sensitive receptor protein that triggers visual phototransductio ...

), an artificial-diet-reared hornworm may have poor vision due to lack of carotenoids in the diet.

As pet food

Captive-bred hornworms fed on an artificial diet are often given to insectivorous exotic animals, such as certain reptiles, fish and small mammals. They are preferred over wild-collected hornworms, which may

bioaccumulate Bioaccumulation is the gradual accumulation of substances, such as pesticides or other chemicals, in an organism. Bioaccumulation occurs when an organism absorbs a substance at a rate faster than that at which the substance is lost or eliminated ...

poisonous substances found in dietary plants. Hornworms, though originally bred for laboratories, are also farmed for this purpose. They are often sold already packed into pods that include everything the larvae need, including food. Care is relatively easy, and animals seem to relish their bright color and flavor.

Subspecies

*''Manduca sexta caestri'' (Blanchard, 1854) (Chile) *''Manduca sexta jamaicensis'' (Butler, 1875) (Caribbean) *''Manduca sexta leucoptera'' (Rothschild & Jordan, 1903) (Galápagos Islands) *''Manduca sexta paphus'' (Cramer, 1779) (South America) *''Manduca sexta saliensis'' (Kernbach, 1964) (Argentina) *''Manduca sexta garapa'' (Pixley, 2016) (Saipan) *''Manduca sexta sexta'' (Americas) Manduca sexta jamaicensis MHNT CUT 2010 0 366 Montvert Martinique France male dorsal.jpg, ''Manduca sexta jamaicensis''
Male dorsal Manduca sexta jamaicensis MHNT CUT 2010 0 366 Montvert Martinique France male ventral.jpg, ''Manduca sexta jamaicensis''
Male ventral Manduca sexta jamaicensis MHNT CUT 2010 0 366 Montvert Martinique France female dorsal.jpg, ''Manduca sexta jamaicensis''
Female dorsal Manduca sexta jamaicensis MHNT CUT 2010 0 366 Montvert Martinique France female ventral.jpg, ''Manduca sexta jamaicensis''
Female ventral Manduca sexta leucoptera MHNT CUT 2010 0 366 Galapagos Isla Santa Cruz (AcademyBay) female dorsal.jpg, ''Manduca sexta leucoptera''
Female dorsal Manduca sexta leucoptera MHNT CUT 2010 0 366 Galapagos Isla Santa Cruz (AcademyBay) female dorsal.jpg, ''Manduca sexta leucoptera''
Female ventral Manduca sexta paphus MHNT CUT 2010 0 366 Planaltino Bahia Brazil male dorsal.jpg, ''Manduca sexta paphus''
Male dorsal Manduca sexta paphus MHNT CUT 2010 0 366 Planaltino Bahia Brazil male ventral.jpg, ''Manduca sexta paphus''
Male ventral

Behavior

Feeding

Tobacco hornworms are facultative specialists; the larvae can grow and develop on any host plants. However, the larvae prefer solanaceous plants, such as tobacco and tomato plants. On these types of plants, larvae grow and develop faster. The lateral and medial

sensilla A sensillum (plural ''sensilla'') is an arthropod sensory organ protruding from the cuticle of exoskeleton, or sometimes lying within or beneath it. Sensilla appear as small hairs or pegs over an individual's body. Inside each sensillum there are ...

styloconia (sensory receptors) on their mouthparts help them to identify solanaceous plants by recognizing indioside D, a steroidal glycoside found in those particular plants (del Campo et al., 2001). Salicin is a distasteful

phagodeterrent Plant defense against herbivory or host-plant resistance (HPR) describes a range of adaptations evolved by plants which improve their survival and reproduction by reducing the impact of herbivores. Plants can sense being touched, and they can ...

, found only in ''

Salix Willows, also called sallows and osiers, from the genus ''Salix'', comprise around 400 speciesMabberley, D.J. 1997. The Plant Book, Cambridge University Press #2: Cambridge. of typically deciduous trees and shrubs, found primarily on moist s ...

'' spp. while

caffeine Caffeine is a central nervous system (CNS) stimulant of the methylxanthine chemical classification, class. It is mainly recreational drug use, used recreationally as a Nootropic, cognitive enhancer, increasing alertness and attentional perfor ...

is a phagodeterrent that is actually toxic. Schoonhoven 1969 found that ''M. sexta'' habituation to salicin is mediated by desensitization of the deterrence associated peripheral neurons and Glendinning et al 1999 the same for caffeine. However Glendinning et al 2001 find only a small peripheral desensitization for salicin, concluding that Schoonhoven erred, and that habituation in this case is centrally mediated. Tobacco hornworms are considered pests because they feed on the upper leaves of tobacco plants and leave green or black droppings on the plants. As adults, they do not damage plants since they feed on nectar. Tobacco hornworm larvae prefer humid environments. When dehydrated, tobacco hornworm larvae will move towards a source of water or to an area with a high relative level of humidity. They use their antennae to locate water to drink (Rowley and Hanson, 2007).

Defense

Nicotine Nicotine is a naturally produced alkaloid in the nightshade family of plants (most predominantly in tobacco and '' Duboisia hopwoodii'') and is widely used recreationally as a stimulant and anxiolytic. As a pharmaceutical drug, it is use ...

is poisonous to most animals that use muscles to move because nicotine targets the acetylcholine receptor at the

neuromuscular junction A neuromuscular junction (or myoneural junction) is a chemical synapse between a motor neuron and a muscle fiber. It allows the motor neuron to transmit a signal to the muscle fiber, causing muscle contraction. Muscles require innervation ...

. However, the tobacco hornworm is capable of metabolizing nicotine from the tobacco plant and using nicotine as a defense against predators. It possesses a gene called cytochrome P450 6B46 (CYP6B46) that converts nicotine into a metabolite. About 0.65% of nicotine metabolites are transported from the gut to the

, where they are reconverted to nicotine and released into the air from the tobacco hornworm's spiracles. The emitted nicotine is used as a way to deter spiders, a practice known as “toxic halitosis.” In one study, tobacco hornworms that fed from nicotine-deficient plants or expressed low levels of CYP6B46 were more susceptible to wolf spider predation (Kumar et al., 2013). Tobacco hornworm caterpillars emit short clicking sounds from their mandibles when they are being attacked. This sound production is believed to be a type of acoustic

aposematism Aposematism is the advertising by an animal to potential predators that it is not worth attacking or eating. This unprofitability may consist of any defences which make the prey difficult to kill and eat, such as toxicity, venom, foul taste ...

, or warning sounds that let predators know that trying to eat them will be troublesome; tobacco hornworms have been observed to thrash and bite predators after producing those clicking sounds. These clicks can be heard at a close distance with a frequency range of 5 to 50 kHz. The intensity of clicks increases with the number of attacks (Bura et al., 2012).

Gallery

File:Britishentomologyvolume5Plate195.jpg, Illustration from John Curtis's ''

British Entomology ''British Entomology'' is a classic work of entomology by John Curtis, FLS. It is subtitled ''Being Illustrations and Descriptions of the Genera of Insects found in Great Britain and Ireland: Containing Coloured Figures from Nature of the Most ...

'' Volume 5, possibly the only British record for this species File:Manduca sexta on tomato.JPG, Feeding on tomato plant File:Tobacco Hornworm Parasitized by Braconid Wasp.jpg, ''Manduca sexta'' parasitized by

braconidae The Braconidae are a family of parasitoid wasps. After the closely related Ichneumonidae, braconids make up the second-largest family in the order Hymenoptera, with about 17,000 recognized species and many thousands more undescribed. One analysis ...

wasp larvae File:Tobacco Hornworm with cocoons.jpg, A tobacco hornworm with wasp cocoons

References

External links

Fact sheet.
Colorado State University.
''Manduca sexta''.
Butterflies and Moths of North America.

Modelling insect wings using the finite element method
{{Taxonbar, from=Q1366539 S Moths of North America Moths of Central America Moths of the Caribbean Sphingidae of South America Animal models Animal models in neuroscience Agricultural pest insects Tomato diseases Pet foods Moths described in 1763 Taxa named by Carl Linnaeus