The Noctuidae are one of the most speciose moth families and include the genera Helicoverpa and Heliothis. Females use (Z)-11-hexadecenal as the major component of their
sex pheromones except for Helicoverpa assulta and Helicoverpa gelotopoeon, both of which utilize
(Z)-9-hexadecenal. The minor compounds found in heliothine
sex pheromone glands vary with species, but
hexadecanal has been found in the
pheromone gland of almost all heliothine females so far investigated. In this study, we found a large amount (0.5-1.5 μg) of
hexadecanal and octadecanal on the legs of males of four heliothine species, Helicoverpa zea, Helicoverpa armigera, H. assulta, and Heliothis virescens. The
hexadecanal was found on and released from the tarsi, and was in much lower levels or not detected on the remaining parts of the leg (tibia, femur, trochanter, and coxa). Lower amounts (0.05-0.5 μg) of
hexadecanal were found on female tarsi. This is the first known
sex pheromone compound to be identified from the legs of nocturnal moths. Large amounts of
butyrate esters (about 16 μg) also were found on tarsi of males with lower amounts on female tarsi. Males deposited the
butyrate esters while walking on a glass surface.
Decapitation did not reduce the levels of
hexadecanal on the tarsi of H. zea males, indicating that
hexadecanal production is not under the same neuroendocrine regulation system as the production of female
sex pheromone. Based on electroantennogram studies, female antennae had a relatively high response to
hexadecanal compared to male antennae. We consider the possible role of
aldehydes and
butyrate esters as courtship signals in heliothine moths.