ABSTRACT

Sensory afferents from the ovipositors influence the behaviour of locusts before and during egg-laying. Contact chemoreceptors, known as basiconic sensilla in insects, occur dispersed and crowded in fields between mechanosensory receptors on the ovipositor of the female desert locust Schistocerca gregaria and serve to control the chemical features of the substrate before and during oviposition. Responses of contact chemoreceptors to aqueous solutions of salts (NaCl), sugars (glucose), acids (citric acid), oviposition aggregation pheromones (veratrole and acetophenone), alkaloids (quinine and tomatine), and phenolic compounds (salicin) were seen. Higher order processing occurs in local and ascending interneurones of the terminal abdominal ganglion. We focussed on a cluster of interneurons extending in the anterolateral region of the eighth abdominal neuromere. Several have ascending collaterals to more anterior abdominal ganglia. The physiological and morphological differences between the chemosensory interneurons suggest that there is no specific centre for processing taste information in the locust terminal ganglion.

Key words: Contact chemoreceptors, locust ovipositor, local and ascending interneurons, chemical stimulants.