ONTOGENIC STUDIES OF FLIGHT INITIATION IN LOCUSTA - WIND RESPONSE OF AN IDENTIFIED INTERNEURON (TCG)

The tritocerebral commissure giant (TCG) wind-sensitive interneurone i s involved in initiation and maintenance of flight in adult locusts. I n this paper we study this interneurone in the imago and non-flying la rval instars. Cobalt fills show that the TCG established its adult mor phology by the first larval instars. Cobalt fills show that the TCG es tablishes its adult morphology by the first larval instar. An accompan ying axon, apparently representing the peculiar tritocerabral commissu re ''dwarf'' (TCD) is present, too, at least for the last preimaginal instars. Physiological tests show similar responses of the TCG to wind stimuli in the 4th, 5th instar and adult stages. Spike activity, howe ver, is usually higher in adult compared to larval instars. It is poss ible that all interneurones, involved in adult-specific motor patterns (such as flight), are present in preimaginal stages and can be activa ted independently of the function of the final motor system.