Foraging for oviposition sites in the Hessian fly: random and non‐random aspects of movement

Abstract

Movements of ovipositing Hessian flies (Diptera: Cecidomyiidae), were 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 plant patches, and (iii) in the density of host plants within arrays of non‐host plants. Durations and frequencies of a range of behaviours were quantified, with the expectation that females would adjust some, but not necessarily all, behaviours when the distribution of host and non‐host plants was altered. Foraging behaviours that were adjusted when plant distribution was altered were seen as evidence for non‐random movement (sensu Morris & Kareiva, 1991), Non‐random components of movement consisted of non‐random settlement on host plants and area‐restricted search after visiting host plants. Ovipositing females also exhibited directed responses to plants; however, directed responses appeared to be based on generalized visual stimuli from grasses rather than species‐specific plant stimuli (e.g. odours). Several behavioural parameters did not change when plant arrays were altered. Females stayed in wheat patches for relatively constant periods of time and laid similar numbers of eggs before leaving wheat patches regardless of the number of plants in the patch or the time taken to find the patch. 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.