Scent Brushes of the Male Tobacco Hornworm Manduca sexta (Lepidoptera: Sphingidae)1

Abstract

The male scent apparatus of Manduca sexta (L.) consists of 2 ventral brushes (hairpencils) arising from the 2nd abdominal segment. They are contained in a pair of slitlike shallow pockets that extend across the 2nd and 3rd segments just lateral to the sternites. The posterior half (3rd segment) of the pocket is lined with minute scales which insert into large glandular cells characterized by a large nucleus, a subapical reservoir lined with microvilli, and a cuticular tubelike extension of the scale that penetrates the cell to the reservoir. The scent brush scales arise from large cells which atrophy shortly after adult eclosion. They are probably nonglandular. Based on the histology, it is concluded that the male scent is produced by the glandular cells at the base of the pocket scales. The scent substance is manufactured in the cell cytoplasm, passes into the reservoir system, and is conducted through the cuticular tube to the pocket scale. At this point, the scent is transferred to the scent brush scales within the pocket and is disseminated when the brushes are everted.