Observations on the life history and ecology of Clubiona pacifica Banks in Washington State (Araneae Clubionidae)

Authors: MILICZKY, EUGENE - Washington State University; Horton, David; WATERS, TIMOTHY - Washington State University; WOHLEB, CARRIE - Washington State University

Submitted to: Journal of Arachnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/20/2020
Publication Date: 6/17/2020
Citation: Miliczky, E., Horton, D.R., Waters, T., Wohleb, C. 2020. Observations on the life history and ecology of Clubiona pacifica Banks in Washington State (Araneae Clubionidae). Journal of Arachnology. 48(1):49-50. https://doi.org/10.1636/0161-8202-48.1.49.
DOI: https://doi.org/10.1636/0161-8202-48.1.49

Interpretive Summary: Several kinds of leafrolling caterpillars are pests in Pacific Northwest apple and pear orchards and can cause significant damage by feeding on the fruit. Scientists with USDA-ARS, Yakima Agricultural Research Laboratory, Wapato, WA in cooperation with scientists at Washington State University, Pasco, WA and Moses Lake, WA, studied the life history of the sac spider Clubiona pacifica, a common spider in riparian areas that often utilizes leaves rolled by such caterpillars as protected sites in which they shed their skins, spend inactive periods, and possibly feed on insects found in the leafrolls including the caterpillars themselves. A series of experiments conducted in the greenhouse under semi-natural conditions showed that most of the spiders used in the experiments fed on pest leafrollers and that adult female spiders can be particularly voracious. In another series of experiments a few spiders fed on leafroller egg masses while many others fed on the tiny, recently hatched caterpillars. Introduction of this spider into orchards or promoting its presence where it already exists may contribute to natural control of pest leafrollers and other orchard pests and reduce the need for insecticide use.

Technical Abstract: We studied aspects of the ecology and life history of the sac spider Clubiona pacifica Banks 1896 in the region east of Mount Rainier National Park in Washington State. Clubiona pacifica has been shown to be a common secondary occupant of lepidopteran leafrolls on alders (Alnus spp.), and examining rolled leaves was found to be an effective way to collect the spider. We collected and examined rolled leaves of alder to determine seasonal phenology of C. pacifica and to examine egg laying and predatory activity. All stages of the spider occurred in rolled leaves, and spiders were found in rolled leaves throughout the season. Rolled alder leaves were used by C. pacifica as protected sites in which to molt and spend inactive periods and possibly to seek prey among the wide variety of secondary arthropod colonists of the leafrolls. Field observations and greenhouse experiments showed that C. pacifica is capable of preying upon leafroller larvae. Occasionally, lepidopteran leafrolls were used by C. pacifica as ready-made chambers in which to oviposit, but more commonly the female spider herself folded an alder leaf to form a protective retreat for oviposition. These egg sac retreats and the associated egg sac are described and illustrated. After eclosion C. pacifica passes through a prelarval stage, a larval stage, and six nymphal stages before reaching adulthood. The principal period of reproduction and egg deposition is June and July, and most post-larval stages of C. pacifica appear to overwinter. We postulate that some individuals require two years to complete their life cycle although others may do so in a shorter time. Three ichneumonid wasps parasitized C. pacifica: Gelis sp. attacked the eggs, while Schizopyga frigida and Zaglyptus varipes parasitized immature and adult spiders.