As one of the natural predators of Asian longhorned beetles Anoplophora glabripennis(Motsch.)(Coleoptera:Cerambycidae),the great spotted woodpecker Picoides major(Linnaeus) is endemic to Wulate Qianqi County and is widely distributed in the artificial shelter-forest of the Inner Mongolian Autonomous Region.From December 2006 to January 2007,the rate of predation on A.glabripennis by P.major was investigated in Wulate Qianqi County in 27 field plots,where P.major and A.glabripennis coexist and in which trees were damaged by A.glabripennis.In addition to the field studies,24 host trees of A.glabripennis were cut down for further examination.Data on the quantities of A.glabripennis,including beetles which were pecked by P.major,were collected from each field plot and every cut-down tree.The data showed that the pecking rate of P.major foraging for A.glabripennis was 14.91% in low damaged plots,19.86% in medium damaged plots and 13.93% in the high damaged plots,respectively.The rate of pecked A.glabripennis found above 6 meters was 27.25%.That was noticeably higher than the rate of pecked A.glabripennis found under 6 meters on the trees,(16.18%).Results also showed that P.major preferred old A.glabripennis larvae over young larvae in both the damaged plots and at greater heights.These results suggest that P.major foraged for A.glabripennis selectively:i) exhibiting a high selectivity in the medium damaged plots;ii) preferentially selecting the appropriate damaged heights;iii) preferentially selecting older larvae,while occasionally selecting a few young larvae.Finally,the reasons of foraging selectivity are discussed in relation to economic factors and methods;such as cost-benefit analysis,trade-off of foraging and risk,and predation risk analysis,based on optimal foraging theory.
