Foraging in a patchy environment

For patch finding, we are beginning to determine the rate at which the fulcrum rolls, and how far it is pushed after successful consumption. Roitberg et al. (1982) show that apple maggot flies search a tree devoid of fruit for approximately four minutes. If introduced into a tree while ovipositing on a hand-held apple (simulating a successful oviposition in the tree), the female searches the tree for about nine minutes. 

Patches of different size and density may differ in findability for insects. For example, dense patches of plants should have longer odor plumes than do sparse patches of equal area. Assuming that an herbivore uses primarily chemical cues when searching for plant patches, Stanton (1982b) predicts from theoretical models of odor-plume geometry that the active space of a dense patch is more likely to be encountered than is the active space of a sparse patch. She points out, however, that an increase in patch density should lead to a less than proportional increase in the active space of the odor plume from the patch. Thus, the probability that a given plant is encountered in the denser patch is less than the probability that a given plant is encountered in the sparse patch. This prediction has yet to be tested experimentally. 

Visual cues from patches of different density have not been analyzed in the same theoretical fashion. However, if color is the most important cue used in patch finding, dense patches should be more easily found than sparse patches because increased plant surface area increases saturation. If pattern or form are more important cues, then dense patches may be more difficult to find because these cues may be more difficult to resolve. The probability of encountering patches of different density depends on the degree to which various visual and/or chemical cues are involved in patch finding. 

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