Effects of Population Density Experienced by Parents during Mating and Oviposition on the Phase of Hatchling Desert Locusts, Schistocerca gregaria

The behavioural phase state of first-instar desert locusts, Schistocerca gregaria Forskål, was quantified by using logistic regression analysis, following treatments in which the population density experienced by their mother during mating and oviposition was manipulated. Crowding during the period of oviposition caused females that had previously been reared in isolation to produce offspring which behaved in a gregarious manner. However, isolating previously crowd-reared females led to hatchlings which behaved more solitariously. The population density experienced during mating affected the behaviour of larvae from solitary-reared, but not crowd-reared, parents. These results show that the transmission of phase characteristics across generations can be modified even at the final stage of the reproductive cycle, providing considerable flexibility in response to changes in population density.