Small-scale vegetation patterns in the parental environment influence the phase state of hatchlings of the desert locust


S. J. Simpson, University Museum and Department of Zoology, Oxford University, Oxford, OX1 3PS, U.K. Fax: +44 (0)1865 310447; e-mail:


Desert locusts (Schistocerca gregaria Forskål (Orthoptera: Acrididae)) change phase in response to population density. Solitarious insects avoid one another; when crowded, they shift to the gregarious phase and aggregate. Laboratory experiments and individual-based modelling have shown that small-scale resource distribution can affect locust phase state via an influence on crowding. Laboratory work has also shown that parental phase state is transmitted to offspring via maternal inheritance. These effects had not been investigated in the field previously. We maintained small populations of adult desert locusts in semi-field enclosures with different distribution patterns of a single plant species (Hyoscyamus muticus L. (Solanaceae)). The offspring of locusts exposed to more clumped patterns of vegetation exhibited more gregarious behaviour when tested in a behavioural phase assay than did progeny from parents left in enclosures with more scattered vegetation. These effects on nymphal behaviour appeared to be mediated by influences of resource distribution on adult phase state. Phase state in small semi-field populations was influenced by small-scale vegetation distribution. Phase differences engendered by environmental structure were maintained in time and transmitted to progeny.