Calling Behavior of Manduca sexta (L.) (Lepidoptera: Sphingidae) with Notes on the Morphology of the Female Sex Pheromone Gland

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Abstract
The calling behavior of the female tobacco hornworm moth, Manduca sexta (L.), is described and correlated with pheromone release. The distribution of calling times over the first seven evenings after eclosion is reported; the females tended to start calling earlier and for a longer period the older they were. During observations over 96 h of continuous darkness, four regularly spaced periods of calling were seen with a mean interval of 25.4 h—a finding consistent with the existence of a circadian rhythm. Electroantennogram bioassays of parts of the female abdominal tip confirm the location of the female sex pheromone gland. The highest pheromonal activity was found in the region of the ventral membrane of the ninth segment, an area previously identified on histological evidence. The gland was examined with light and scanning electron microscopy. It is a modification of the ventral membrane of the ninth abdominal segment and consists of a monolayer of cuboid to columnar cells lining the cuticle. The surface of the intersegmental membrane is covered by small spines, some of which appear to have droplets at their tips. A second area of glandular appearance also was found underlying the anal papillae of the ninth segment.