Naming*''Manduca sexta caestri''
⤷ ''Manduca sexta jamaicensis''
⤷ ''Manduca sexta leucoptera''
⤷ ''Manduca sexta paphus''
⤷ ''Manduca sexta saliensis''
⤷ ''Manduca sexta sexta''
Behavior''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.
Reproduction''M. sexta'' eggs are spherical, approximately 1.5 millimeters in diameter, and translucent green in color. 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.''M. sexta'' larvae are green in color and grow up to 70 millimeters in length. Under laboratory conditions, when fed a wheat-germ based diet, larvae are turquoise due to a lack of pigments in their diet. ''M. sexta'' hemolymph contains the blue-colored protein insecticyanin. When the larva feeds on plants, it ingests pigmentacious carotenoids. Carotenoids are primarily yellow in hue. The resulting combination is green.
During the larval stage, ''M. sexta'' caterpillars feed on plants of the family Solanaceae, principally tobacco, tomatoes and members of the genus ''Datura''. ''M. sexta'' has five larval instars, which are separated by ecdysis , but may add larval instars when nutrient conditions are poor. Near the end of this stage, the caterpillar seeks a location for pupation, burrows underground, and pupates. The searching behaviour is known as "wandering". The imminence of pupation suggested behaviorally by the wandering can be anatomically confirmed by spotting the heart , which is a long, pulsating vessel 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.
A common biological control for hornworms is the parasitic 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. Another wasp species, ''Polistes erythrocephalus,'' feeds on hornworm larvae.
FoodTobacco 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 styloconia, which are sensory receptors, on their mouthparts help them to identify solanaceous plants by recognizing indioside D, a steroidal glycoside found in those particular plants . 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 .
DefenseNicotine is poisonous to most animals that use muscles to move because nicotine targets the acetylcholine receptor at the neuromuscular junction. 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 that converts nicotine into a metabolite. About 0.65% of nicotine metabolites are transported from the gut to the hemolymph, 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 .
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, 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 .
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