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Population Densities of Spiders (Araneae) and Spruce Budworms (Lepidoptera, Tortricidae) on Foliage of Balsam Fir and Red Spruce in East-Central Maine

Daniel T. Jennings, John B. Dimond and Bruce A. Watt
The Journal of Arachnology
Vol. 18, No. 2 (Summer, 1990), pp. 181-193
Stable URL: http://www.jstor.org/stable/3705836
Page Count: 13
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Population Densities of Spiders (Araneae) and Spruce Budworms (Lepidoptera, Tortricidae) on Foliage of Balsam Fir and Red Spruce in East-Central Maine
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Abstract

Spiders of 10 families, 17 genera, and at least 22 species were collected from crown foliage samples of Abies balsamea (L.) Mill. and Picea rubens Sarg. in east-central Maine. Species of web spinners were more prevalent (68.2% of total species) among branch samples (N = 613 branches) than species of hunters (31.8%). Mean species per site (N = 8 sites) was 7.6 ± 1.2. Numbers, life stages, and sex ratios of spiders differed between tree species; sex ratios were biased (G-test, P ≤ 0.001) in favor of females. Spider densities per m2 of foliage area generally were greater (P ≤ 0.05) on red spruce (X̄ = 12.0 ± 1.3) than on balsam fir (X̄ = 7.2 ± 0.9), but sampling intensity was important. For intensely sampled sites, overall mean densities of spruce budworms / m2 of foliage were not significantly different (P > 0.05) between tree species. Spearman's rank correlation coefficients indicated that spider-budworm densities covaried weakly among study sites for each tree species; balsam fir ((rho) = 0.17, N = 343), red spruce ((rho) = 0.15, N = 270). Enhancement of spider populations through silvicultural treatments designed to favor spruces is proposed.

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