Submitted to: Annals of the Entomological Society of America
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2000
Publication Date: 3/1/2001
Citation: Horton, D.R., Miliczky, E.R., Broers, D.A., Lewis, R.R., Calkins, C.O. 2001. Numbers, diversity, and phenology of spiders (Araneae) overwintering in cardboard bands placed in pear and apple orchards of central Washington. Annals of the Entomological Society of America. 95:469-480. Interpretive Summary: Spiders are among the most abundant predators in orchards if insecticide use is curtailed. However, life history processes that determine which species of spiders are common in orchards are not known. One such process likely to be important in affecting numbers of spiders in orchards is overwintering success. We placed artificial overwintering shelters constructed of corrugated cardboard in pear and apple orchards of the Yakima Valley. The bands were readily colonized by a diverse population of spiders, dominated by crab spiders and jumping spiders. By collecting and replacing shelters at weekly intervals, we determined when (in autumn) spiders began moving into shelters for hibernation. Much of the movement into shelters occurred in late-October to late-November, coinciding approximately with leaf fall in the orchard. Spiders hibernated at several heights in the tree. Counts of overwintering spiders were larger in orchards that received no insecticides during the growing season than in orchards that received even small amounts of insecticides.
Technical Abstract: Cardboard bands were placed in pear and apple trees to act as overwintering shelters for spiders. Bands were placed on the trees in late Aug., at 3-heights in the tree. Two-thirds of the bands were replaced at weekly intervals to monitor phenology of movement into the shelters. One-third of the bands were collected in Jan. to determine what taxa of spiders overwintered in the shelters. Over 2900 spiders in 10 families were recovered from the winter-collected set of bands; spiders overwintered at all 3- heights in the tree. The majority of spiders were juveniles, although adults of some Salticidae were common. Dominant families were Philodromidae and Salticidae. In the weekly collections, over 5600 bands were sampled during the study, and these bands produced over 6000 spiders represented by twelve families and 30 identified genera. Dominant taxa included Philodromus cespitum, P. aeneola, Xysticus spp. (Thomisidae), Sassacus papenhoei (Salticidae), Phidippus spp. (Salticidae), and Anyphaena pacifica (Anyphaenidae). Of these taxa, Xysticus spp., S. papenhoei, and A. pacifica were uncommon in the winter-collected bands, suggesting that these spiders used the bands as temporary refuges only, and overwintered elsewhere. Results suggested that Philodromus spp., Dictyna spp., P. aeneola, and Cheiracanthium mildei entered overwintering shelters between mid-Oct. and mid- to late-Nov. Counts of spiders were considerably higher in the unmanaged and organic orchards than in the orchard that received insecticides during the growing season.