摘要：

The functional response and search strategy of the predator attacking 3rd-instar of was measured in the laboratory and in a potato field in Iowa. In laboratory Petri dish arenas, predators attacked more prey as prey density increased, attacking a maximum of 7.43 prey in 24 h. Estimates of the area searched declined as prey density increased. The decline in search could be attributed to the accumulated time predators spent handling prey. The functional response of the predator in the field did not resemble that measured in the laboratory. In the field, predators attacked a relatively constant number of prey, regardless of the number of prey provided. Like in the laboratory, the estimated area the predator searched declined as prey density increased. However, in contrast to the laboratory situation, the decline in search could not be attributed to the accumulated time predators spent handling prey as they attacked so few prey in the field. A model of predator search in the field was used to explain the relationship between predator search and prey density. Results are compared with similar measures of the attack rates and the search strategies of and other species of predators in a different crop, soyabeans. Regardless of the predator, prey, or crop, the same search strategy and level of attack was observed. The similarity in attack rates and search strategies in different predator-prey systems and the difference between laboratory and field measurements of the functional response of a predator are discussed with reference to the use of predators in biological control.

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