Laboratory studies on pheromones and reproduction in the Desert Locust Schistocerca gregaria (Forsk.)

Abstract

AbstractAfter reviewing the literature special breeding experiments in temperature gradients were carried out with mated and virgin females of Schistocerca gregaria under various laboratory conditions. The reproduction activity was calculated from all laid egg‐pods and eggs; it was highest in normal mated females. In unmated females egg‐pod production increased in the presence of males by means of a male chemical factor. Mislaid egg‐pods were highest in females without antennae and in virgin females near to males. Mated females without antennae produced much fewer egg‐pods than normal ones; the mean number of eggs was also lower.Egg‐pods were deposited from the 3rd to the 20th week after emergence, with a mean of about 10–13 weeks in virgin females and 8–9 in mated ones. The weekly number of eggs per pod varied from 28–70; a high number of eggs per pod was correlated to a low production rate of egg‐pods.The egg‐laying interval was shorter in mated than in virgin females; in the latter it was shortened in the presence of males.The hatching rate of nymphs was higher from fertilized eggs (66.2%) than unfertilized ones (22.2%); from parthenogenetic eggs only females hatched. As adults they can again produce offspring over generations without mating.The nymphal development lasted about 1 month. In mated females the adult rate was 64.1% and in virgin ones only 20.8% related to the hopper number at the beginning. Generally the adult female rate of the progeny of virgin females was about 70% lower than that of the mated females, when the reduced rate of fecundity, fertility and emergence to adults were considered.The mean adult lifespan was calculated at about 5 months for virgin females (3 month egg‐laying period) and 1 month less for mated ones.