CENTRAL PROCESSING OF SEX-PHEROMONE, HOST ODOR, AND OVIPOSITION DETERRENT INFORMATION BY INTERNEURONS IN THE ANTENNAL LOBE OF FEMALE SPODOPTERA-LITTORALIS (LEPIDOPTERA, NOCTUIDAE)

Physiological and anatomical characteristics of antennal lobe interneu rons in female Spodoptera littoralis (Boisd.) were investigated using intracellular recording and staining techniques. Responses of local in terneurons and projection neurons to female sex pheromone components, host plant odours, and behaviourally active oviposition deterrents wer e recorded. We found local interneurons and projection neurons that re sponded specifically to only one or two of the tested odours, but we a lso found less specific cells, and neurons that responded to most of t he tested odourants. These findings show that there are not only speci fic olfactory pathways in female moths up to the protocerebral level, but also that integration can begin in the antennal lobe. No correlati on was found between the degree of specificity of either local interne urons or projection neurons and their respective morphological charact eristics. Specialized and unspecialized local interneurons arborized t hroughout the antennal lobe. Specialized and unspecialized projection neurons had uniglomerular arborizations in the antennal lobe and sent their axons to the calyces of the mushroom body, and to the lateral ho rn of the protocerebrum. One specific projection neuron had multiglome rular arborizations and projected only to the lateral horn of the prot ocerebrum. Projection neurons arborizing in the glomeruli closest to t he entrance of the antennal nerve always responded to pheromone compon ents. No other correlations were found between the arborization patter n of projection neurons in the antennal lobe or in the protocerebrum a nd their response characteristics. The sensitivity of local interneuro ns and projection neurons was in the same range as that of receptor ne urons in olfactory sensilla on the antennae, suggesting a much lower c onvergence in the central nervous system in females than in the pherom one-processing pathway in males. (C) 1994 Wiley-Liss, Inc.