Field observations on Harmonia axyridis Pallas (Coleoptera: Coccinellidae) in Oregon

A lady beetle native to Asia, Harmonia axyridisPallas, is established in the Pacific Northwest of NorthAmerica. Ten years occurred between the intentionalrelease of beetles and the first observation of an indi-vidual on July 18, 1991, in Kings County, Washington.The beetle was extremely abundant in western Wash-ington and Oregon throughout 1993-1994, where thespecies ranged from mideastern Washington, south tojust north of the California/Oregon border, east to anelevation of 1371 m in the Cascade Mountains and westto the Pacific Coast. Field sampling confirmed thehabits and habitats of H. axyridis as a generalist,semiarboreal, aphidophagous predator. Our recordsassociate H. axyridis with 17 aphid prey species on 17plant hosts. In western Oregon, H. axyridis co-occurswith 11 species of native and 2 species of exotic aphido-phagous coccinellids on trees and shrubs. In arborealhabitats, 70% of individual lady beetles and 82% of liveadult coccinellid mass were represented by H. axyri-dis, while constituting only 4% of the coccinellids inalfalfa, clover, and peppermint. Adult H. axyridis dis-persed to feeding sites from overwintering aggrega-tions, which formed the preceding October, duringMarch. At least two generations, with a partial tocomplete third generation, occur per year. Parasitismof field-collected adult beetles by Dinocampus coccinel-
lae (Schrank) was less than 1%. © 1996 Academic Press, Inc.KEY WORDS: Insecta; Coccinellidae; Harmonia axyri-dis; Dinocampus; guild; biocontrol; polymorphism.