Date of Award

8-2002

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Ecology and Environmental Sciences

Advisor

A. Randall Alford

Second Committee Member

Francis A. Drummond

Third Committee Member

Daniel J. Harrison

Abstract

The ecology of spiders (Araneae) in lowbush blueberry (Vaccinium angustifolium (Aiton)) fields in Washington County, Maine, was studied during the summers of 2000 and 2001. The abundance and distribution of spiders was investigated, and predation by one family of spiders, the wolf spiders (Lycosidae) was evaluated. The abundance and distribution of spiders was examined by capturing spiders using pitfall traps. Traps were set in conventionally managed, reduced input, and organic fields at different distances from the field edge (forest border or windbreak). The most commonly captured spiders were in the family Lycosidae. More lycosids were captured in May, June, and July than in August. Lycosids were more abundant in reduced input fields than in conventional fields in 2000 and 2001. No differences in capture were detected among conventionally managed, reduced input, and organic fields for samples taken in the later part of the season in 2001. Species composition of lycosid communities were not significantly different among fields and management practices in 2000, but the proportion of each species captured differed among management practices in 2001. Significantly more lycosids were captured at field edges than the field interior. In both 2000 and 2001, there was a significant linear contrast with lycosid capture decreasing as distance from the edge increased. In each year, one conventional field showed this linear decline in lycosid capture as distance from the edge increased, but the reduced input and organic fields did not. There were no significant differences in community composition between distances from the edge, but some species were associated with specific distances. Field edges may be a more important habitat from lycosids in blueberry fields that are more intensely managed. Predation by wolf spiders (Lycosidae) on pest and non-pest insects found in blueberry fields in Washington County, Maine, was investigated in the laboratory, greenhouse, and field. In laboratory experiments, four taxa of prey insects were evaluated as prey in no-choice arenas. Prey examined were blueberry spanworm ltame argillacearia (Packard) (Lepidoptera: Geometridae), blueberry flea beetle larvae, Altica sylvia Malloch (Coleoptera: Chrysomelidae), grasshopper (Acrididae) adults and nymphs, and field cricket (Gryllus pennsylvanicus Burmeister) (Orthoptera: Gryllidae) adults and nymphs. Lycosids consumed blueberry flea beetles, grasshopper nymphs, and field cricket nymphs but not blueberry spanworm, grasshopper adults, or field cricket adults. In greenhouse mesocosms, both grasshopper and house cricket (Acheta domestica Linnaeus) densities were lower in no-choice cages containing a single lycosid compared to control cages with no spiders; blueberry spanworm larvae densities remained the same. Two field experiments were conducted in which cages received known quantities of several prey species and either zero (control), four, or eight lycosids. Significant differences in numbers of grasshoppers or house crickets recovered were not detected among treatments. There were significant differences in field crickets recovered. Less field crickets remained in cages containing more predators (lycosids, carabid beetles, and ants). Although lycosids consumed some blueberry pest species, pest populations were not significantly lower in field cages containing lycosids.

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