In 1984, Nathanson reported an effect of methylxanthines on larvae of the tobacco hornworm. Juvenile hormone-specific esterases in the haemolymph of the tobacco hornworm, Manduca sexta. Riddiford studies the endocrinology of insects, specifically the tobacco hornworm. Tomato hornworms are closely related to (and sometimes confused with) the tobacco hornworm "Manduca sexta". Tobacco hornworm caterpillars emit short clicking sounds from their mandibles when they are being attacked. The tobacco hornworm is sometimes kept as a pet by children throughout its range.