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

Desert locusts (Schistocerca gregaria Forskal (Orthoptera: Acrididae)) chan ge phase in response to population density. Solitarious insects avoid one a nother; when crowded, they shift to the gregarious phase and aggregate. Lab oratory experiments and individual-based modelling have shown that small-sc ale resource distribution can affect locust phase state via an influence on crowding. Laboratory work has also shown that parental phase state is tran smitted to offspring via maternal inheritance. These effects had not been i nvestigated in the field previously. We maintained small populations of adu lt desert locusts in semi-field enclosures with different distribution patt erns of a single plant species (Hyoscyamus muticus L. (Solanaceae)). The of fspring of locusts exposed to more clumped patterns of vegetation exhibited more gregarious behaviour when tested in a behavioural phase assay than di d progeny from parents left in enclosures with more scattered vegetation. T hese 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 d ifferences engendered by environmental structure were maintained in time an d transmitted to progeny.