PHYSIOLOGICAL-RESPONSES AND CENTRAL NERVOUS PROJECTIONS OF ANTENNAL OLFACTORY RECEPTOR NEURONS IN THE ADULT DESERT LOCUST, SCHISTOCERCA-GREGARIA (ORTHOPTERA, ACRIDIDAE)

Olfactory receptor neurons present in two morphological sensillum type s on the male Schistocerca gregaria antenna were for the first time in vestigated physiologically when stimulated with behaviourally relevant odours. Neurons present in trichoid/basiconic sensilla showed clear e xcitatory responses to compounds present in the male-produced aggregat ion pheromone and also to a plant produced compound. Sensilla could be categorised physiologically according to the responses of their recep tor neurons to the tested stimuli. Also receptor neurons present in se nsilla coeloconica responded to aggregation pheromone components, but always in an inhibitory fashion. These neurons could, however, be exci ted by a plant produced compound and by some acids present in the nymp hal odour. The antennal lobe of the male S. gregaria was observed to c ontain about 1000 very small glomerular structures. Single receptor ne urons were stained from the antenna to the antennal lobe using a cobal t lysine technique. These stainings revealed a multi glomerular axonal branching pattern of antennal receptor neurons.