FORAGING FOR OVIPOSITION SITES IN THE HESSIAN FLY - RANDOM AND NONRANDOM ASPECTS OF MOVEMENT

1. Movements of ovipositing Hessian flies (Diptera: Cecidomyiidae), we re quantified in plant arrays that varied in one of three ways: (i) in distances between patches of host plants, (ii) in the size of host pl ant patches, and (iii) in the density of host plants within arrays of non-host plants. Durations and frequencies of a range of behaviours we re quantified, with the expectation that females would adjust some, bu t not necessarily all, behaviours when the distribution of host and no n-host plants was altered. 2. Foraging behaviours that were adjusted w hen plant distribution was altered were seen as evidence for non-rando m movement (sensu Morris & Kareiva, 1991). Non-random components of mo vement consisted of non-random settlement on host plants and area-rest ricted search after visiting host plants. Ovipositing females also exh ibited directed responses to plants; however, directed responses appea red to be based on generalized visual stimuli from grasses rather than species-specific plant stimuli (e.g. odours). 3. Several behavioural parameters did not change when plant arrays were altered. Females stay ed in wheal patches for relatively constant periods of time and laid s imilar numbers of eggs before leaving wheat patches regardless of the number of plants in the patch or the time taken to find the patch. 4. Non-random movements resulted in the placement of eggs on hosts rather than non-hosts, while random movement contributed to egg laying over larger areas.