Prey of the spider, Dictyna coloradensis, on apple, pear, and weeds inCentral Washington (Araneae : Dictynidae)

摘要

The cribellate spider, Dictyna coloradensis Chamberlin, constructed webs on the upper surface of apple and pear leaves (trees not treated with insecticide), and on weeds in adjacent, uncultivated ground, at a site in south central Washington. Prey found in D. coloradensis webs were assigned to one of three categories: pests, predators and parasitoids, or neutral in impact with respect to fruit trees. Pest taxa comprised 32%, predators and parasitoids 24%, and neutral groups 44% of 18,314 prey. Most prey were small, winged insects (length < 5 mm). Insects from 58 families in 10 orders were represented and small spiders in four families were occasionally trapped. Sciaridae and Chironomidae (Diptera) were the most numerous prey and made up 37% of the total. Most webs contained one or more of these flies and occasionally 25 or more were trapped. Alate aphids were the most frequently captured pest insects. Other pests included adults of the white apple leafhopper, the pear psylla, and thrips. Relatively non-mobile stages of the pests (leafhopper and pear psylla nymphs and apterous aphids) were less commonly found in the webs. Nineteen percent of all prey were parasitoid wasps, 14 families of which were identified. Known parasitoids of apple and pear pests were included. The only other predator or parasitoid taxon that comprised more than 1% of total prey was the Empididae (3%).