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 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 (CYP6B46) 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 (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, 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 References Further reading External links Fact sheet. Colorado State University. Manduca sexta. Butterflies and Moths of North America. Microscopy. Modelling insect wings using the finite element method 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