Haemolymph ecdysteroids and the prothoracic glands in the solitary and gregarious adults of Schistocerca gregaria

The haemolymph titre of ecdysteroids rises in the adults of both sexes to a brief peak in the first week after emergence. A major rise begins on days 8–10, coincidentally with intensive vitellogenesis in the females and aggregation pheromone production in the males. The titre reaches about 400 ng of 20-hydroxyecdysone (20E) equiv./ml in the solitary, but less than 150 ng/ml in the gregarious adults of both sexes. In the females, the titre drops after oviposition (prior to day 20) and remains low until the next egg batch matures; then it increases in either phase to 150–180 ng/ml. A similar titre reduction in the males occurs just after day 20: in the solitary males the titre declines slowly to about 110 ng/ml on day 40, whereas in the gregarious males ecdysteroids virtually disappear by day 25. The blood of females contains similar levels of 20E and ecdysone, whereas in the males 20E makes up 73% (solitary) or 94% (gregarious) of total ecdysteroids. Minor components include a compound behaving as makisterone A and highly polar metabolites. The prothoracic glands are well preserved in both solitary and gregarious adults for at least 1 week after fledging and in some females they seem to persist for the lifetime, but in contrast to the glands of larvae, do not produce significant amounts of ecdysteroids when cultured in vitro .