Sexually dimorphic and isomorphic glomeruli in the antennal lobes of the sphinx moth Manduca sexta

Antennal lobes of adult male and female Manduca sexta were compared in orde r to investigate the nature and extent of sexual dimorphism of the primary olfactory center of this lepidopteran species. Complete identification of t he glomeruli led to the conclusion that all female glomeruli have homologou s male counterparts. Thus, there is no sex-specific glomerulus present in o ne sex and absent in the other. Sexual dimorphism (i.e. glomeruli present b ut morphologically different in males and females), however, does occur in the three glomeruli composing the male macroglomerular complex. The female homologs of this complex consist of two previously identified 'large female glomeruli' and one newly identified normal-sized glomerulus. The lateral a nd medial targe female glomeruli are interpreted to be homologous to the fi rst two macroglomerular-complex glomeruli-the cumulus and toroid 1. The thi rd male component, the toroid 2, was tentatively identified with a normal-s ized spheroidal glomerulus of the female, called here the 'small female glo merulus'. The 60 'ordinary' qlomeruli that make up the rest of the glomerul ar neuropil were found to be homologous in males and females, with the exce ption of two anomalous (or uncertain) glomeruli. Some variations in relativ e position and size observed among those glomeruli suggest a diffuse. quant itative kind of sexual dimorphism.