ECOLOGY AND POPULATION BIOLOGY Seasonal Distribution of Anthocoris spp. and Deraeocoris brevis (Heteroptera: Anthocoridae, Miridae) in Orchard and Non-Orchard Habitats of Central Washington

Occurrence of Anthocoris tomentosus Péricart, A. antevolens White, A. whitei Reuter, and Deraeocoris brevis (Uhler) in non-orchard habitats is described for areas adjacent to the pear growing regions of Yakima, WA. The four species were found on a number of tree and shrub species, especiallywillow, cottonwood, oak, alder, aspen, poplar, andbitterbrush. The four predators differed in degree of specialization. A. whitei was found almost exclusively on antelope bitterbrush (Purshia tridentata Pursh), apparently in close association with an unidentiÞed psyllid. The other two anthocorids were more generalized, but differed in occurrence on some tree species. Adult and immature A. antevolens were common on oak, cottonwood, and poplar. Conversely, A. tomentosus was comparatively uncommon on these species, but was more abundant than A. antevolens on the neighboring willows; immatures of A. tomentosus were never recovered from oak. Adult and immature D. brevis were collected from several species not shown to support populations of Anthocoris spp., suggesting that themirid ismore of a generalist than the anthocorids.Anthocoris spp. were rare in apple orchards, whereas D. brevis was common there. A. tomentosus and A. antevolens showeddistinct seasonal changes in plant use. Both species congregated onwillow catkins beginning in March, but began to appear on summer hosts (oak, cottonwood, alder, aspen, poplar) in May and June. Someof themovement fromwillowmayhavebeen a result of thedisappearanceof a univoltine psyllid from this host plant. Traps composed of corrugated cardboard were placed at different sites to collect overwintering predators. A. antevolens and D. brevis were more broadly distributed among plant species than A. tomentosus or A. whitei (the latter restricted to pear and bitterbrush). A. antevolens was very abundant in traps collected from poplar and cottonwood, apparently because both tree species are important sources of late-summer prey for this predator. Other miscellaneous Anthocoridae and Deraeocoris spp. were collected while sampling, and lists of these species are provided. Orius tristicolor (White) was common at several sites, and was easily the most abundant anthocorid in overwintering traps at one intensively sampled orchard. This species was particularly abundant in traps placed in peach trees. Overwintering sex ratios of D. brevis, Anthocoris spp., and O. tristicolor were moderately to strongly female-biased.