CENTRAL NERVOUS PROCESSING OF BEHAVIORALLY RELEVANT ODORS IN SOLITARYAND GREGARIOUS 5TH INSTAR LOCUSTS, SCHISTOCERCA-GREGARIA

Physiological and morphological characteristics of antennal lobe neuro ns of solitary and gregarious fifth-instar nymphs of the desert locust , Schistocerca gregaria, were studied using intracellular recording an d staining techniques. Physiological characteristics of antennal lobe neurons of both locust phases responding to stage-dependent aggregatio n pheromones, egg-laying attractants, a putative sex pheromone and pla nt-associated volatiles are described. Antennal lobe neurons showed ex citatory, inhibitory, combined excitatory and inhibitory and delayed r esponses. In addition, one neuron showing an initial inhibition follow ed by an excitation and inhibition response was found. Pheromone-speci fic-, plant-specific- and pheromone-plant-generalist neurons were foun d in both locust phases. Antennal lobe neurons displayed stage- and ph ase-dependent differences in the processing of aggregation pheromone c omponent input. Nymphal antennal lobe neurons showed stage-dependent r esponse characteristics highly correlated with the preferential behavi oural attraction to the nymphal aggregation pheromone. Phase-dependent differences were found in the response spectra and the sensitivity of the same neuron types. Neurons of solitary locusts responded signific antly more frequently to some of the tested components than neurons of gregarious locusts. Furthermore, antennal lobe neurons of solitary lo custs showed a higher sensitivity to most of the tested compounds.