Numbers, Diversity, and Phenology of Spiders (Araneae) Overwintering in Cardboard Bands Placed in Pear and Apple Orchards of Central Washington

Abstract

Cardboard bands were placed on pear and apple trees at each of three sites to act as overwintering shelters for spiders. Bands were placed on the trees in late August, at three heights on the tree. One-third of the bands was collected in January to determine what taxa of spiders overwintered in the shelters. The remaining bands at each site were collected and replaced at weekly intervals between late August and early December to monitor phenology of movement into the shelters. More than 2,900 spiders in 10 families were recovered from the winter-collected set of bands. Spiders were collected from all three sampling heights in the trees. The majority of spiders were juveniles, although adults of some Salticidae [especially Pelegrina aeneola (Curtis) and Phanias sp.] were fairly common. The dominant families were Philodromidae (primarily Philodromus spp.) and Salticidae (primarily P. aeneola), comprising 66 and 28%, respectively, of the total specimens. In the weekly collections, >5,600 bands were sampled during the study producing >6,000 spiders represented by 12 families and 30 identified genera. Dominant taxa in the weekly collected bands included Philodromus cespitum (Walckenaer), P. aeneola,Xysticus spp. (Thomisidae), Sassacus papenhoei Peckham and Peckham (Salticidae), Phidippus spp. (Salticidae), and Anyphaena pacifica Banks (Anyphaenidae). Of these taxa, Xysticus spp., S. papenhoei, and A. pacifica were very uncommon in the winter-collected bands, and we infer from these results that these spiders used the bands as temporary refuges only, and overwintered elsewhere. Data obtained from the weekly collected bands suggested that Philodromus spp., Dictyna spp., P. aeneola, and Cheiracanthium mildei L. Koch entered overwintering shelters during the interval between mid-October and mid- to late November. Pear and apple blocks at the same site were more similar in community composition than a common crop species at two different sites. More spiders were recovered from bands placed in the unmanaged and organically managed orchards than from apple and pear blocks that received insecticides during the growing season.