ANTENNAL LOBE PROJECTION PATTERNS OF OLFACTORY RECEPTOR NEURONS INVOLVED IN SEX-PHEROMONE DETECTION IN SPODOPTERA-LITTORALIS (LEPIDOPTERA, NOCTUIDAE)

Pheromone-specific receptor neurons in male and female cotton leafworm s, Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae) were typed physiologically and traced into the antennal robe using cobalt lysine as a marker. In male S. littoralis, the macroglomerular complex (MGC), which is responsible for the initial integration of information conce rning sex pheromone components, contains three glomerular compartments as revealed in a morphological study. No such specialized structure w as seen in the female. In the male, olfactory receptor neurons that re sponded selectively to stimulation with the major sex pheromone compon ent, (Z)9, (E)11-tetradecadienyl acetate (Z9E11-14:OAc), had arborizat ions that were restricted to a large glomerulus of the MGC (designated a), situated near the antennal nerve entrance into the antennal lobe. Neurons that were stimulated by (Z)9,(E)12-tetradecadienyl acetate (Z 9E12-14:OAc), a second pheromone component, had arborizations in a lat eral, smaller glomerulus of the MGC (designated c), while receptor neu rons specifically tuned to a behavioural antagonist, (Z)-9-tetradeceno l (Z9-14:OH), projected to a medial glomerulus of the MGC (b). In the female, receptor neurons tuned to the major pheromone component projec ted to a glomerulus situated at the entrance of the antennal nerve. Th is glomerulus did, however, not have the size or the structure of the male MGC. A second neuron housed in the same sensillum projected its a xon to an ordinary glomerulus situated medially in the antennal lobe.