This work examined the importance of structural complexity of habitat, availability of prey, and competition with ants as factors influencing the abundance and community composition of arboreal spiders in western Oregon. In 1993, I compared the spider communities of several host-tree species which have different branch structure. I also assessed the importance of several habitat variables as predictors of spider abundance and diversity on and among individual tree species. The greatest abundance and species richness of spiders per 1-m-long branch tips were found on structurally more complex tree species, including Douglas-fir, Pseudotsuga menziesii (Mirbel) Franco and noble fir, Abies procera Rehder. Spider densities, species richness and diversity positively correlated with the amount of foliage, branch twigs and prey densities on individual tree species. The amount of branch twigs alone explained almost 70% of the variation in the total spider abundance across five tree species. In 1994, I experimentally tested the importance of needle density and branching complexity of Douglas-fir branches on the abundance and community structure of spiders and their potential prey organisms. This was accomplished by either removing needles, by thinning branches or by tying branches. Tying branches resulted in a significant increase in the abundance of spiders and their prey. Densities of spiders and their prey were reduced by removal of needles and thinning. The spider community of needle-sparse branches was dominated by orb weavers (Araneidae), whereas tied branches were preferably colonized by sheet-web weavers (Linyphiidae and Micryphantidae), and nocturnal hunting spiders (Anyphaeilidae and Clubionidae). Spider species richness and diversity increased in structurally more complex habitats. In 1994 and 1995, I excluded foraging Camponotus spp. ants from canopies of sapling Douglas-fir. Biomass of potential prey organisms, dominated by Psocoptera, increased significantly by 1.9 to 2.4-fold on the foliage following ant exclusion. Hunting spiders, dominated by the Salticidae, increased significantly by 1.5 to 1.8-fold in trees without ants in the late summer. The exclusion of ants did not affect the abundance of web-building spiders. Documented aggressive behavior of aphid-tending ants suggests interference competition between hunting spiders and ants. / Graduation date: 1996

A randomized block experiment was conducted in cabbage fields at Texas Agriculture Experiment Station at Weslaco in the spring and fall 2005 and spring 2006. There were four blocks and two pesticide treatments, spinosad (SpinTor®), lambda- cyhalothrin (Warrior®), and an untreated control. The pesticide treatments were for the management of Plutella xylostella L. (Lepidoptera: Plutellidae) and Trichoplusia ni (Hubner) (Lepidoptera: Noctuidae). Pitfall traps captured eight families of spiders in fall 2005, and thirteen families in spring 2006. The most abundant family was Lycosidae with Pardosa delicatula (Gertsch and Wallace) followed by Pardosa pauxilla (Montgomery) and Hogna helluo (Walckenaer) in fall 2005, while in spring 2006 Hogna helluo was most abundant followed by Pardosa delicatula and Pardosa pauxilla. The diversity of spiders in fall 2006 in the lambda-cyhalothrin plots was lower than that of spiders found in the untreated control or the spinosad treated plots, which were up to 2.6 and 2.4 times, respectively, more diverse. In spring 2006, the spiders in untreated control and spinosad treated plots were 1.5 and 1.3 times respectively more diverse than spiders in the lambda-cyhalothrin treated plots. In fall 2005, mean diversity of spiders in spinosad treated plots was 1.1 times more diverse than in the untreated control, although this difference was not statistically significant. In spring 2006, spinosad treated plots had 1.2 times greater diversity than untreated control and this difference was significant. The effects of two insecticide treatments on height, width, and weight of cabbages were highly significant in all three seasons. Cabbage harvest in spinosad and lambda- cyhalothrin plots showed greater height, width, and weight than in untreated control but were not different from each other. However, in the larval damage rating, spinosad treatment showed better management of diamondback moth and cabbage looper than lambda- cyhalothrin.

Thesis (M.S.)--Miami University, Dept. of Zoology, 2003. / Title from first page of PDF document. Document formatted into pages; contains vii, 58 p. Includes bibliographical references (p. 52-58).

Thesis (Ph. D.)--Ohio State University, 2004. / Title from first page of PDF file. Document formatted into pages; contains xii, 138 p.; also includes graphics. Includes abstract and vita. Advisor: Richard A. Bradley, Dept. of Evolution, Ecology, and Organismal Biology. Includes bibliographical references (p. 124-138).

No description available.

Aspects of the distribution and ecology of some surface-dwelling invertebrates were examined on different high-altitude vegetation types in the north Pennines, England. The influence of the boundary between habitats on the invertebrate community was also investigated, and the effects of habitat heterogeneity on invertebrate distribution were discussed. Spiders and carabids were sampled from the dominant vegetation types on the plateaux of three mountain summits (Cross Fell, Littie Dun Fell and Great Dun Fell) in 1991 using pitfall traps. Multivariate methods were used to classify and ordinate the sites based on their fauna and to assess the influence of the local environmental variation on the species distribution. Three spider assemblages were recognised based on their common species composition; two short Festuca grassland assemblages and a Nardus/Eriophorum assemblage associated with greater vegetation density. The results suggest that variation in the vegetation structure is the major factor influencing spider distribution on the summit plateaux, with slope and soil depth also contributing. The carabids appeared too widely distributed to assign to any specific vegetation types. The influence of the interface between different vegetation types on the spider and carabid fauna was sampled using pitfall traps in 1992-3. At the boundary between two highly contrasting habitats (sheep pastures and conifer plantations) an edge effect was found in both groups, where species richness was elevated. The major contribution to this increase was the mixing of both pasture and plantation species, species specific to the interface were few. The edge effect at this interface was narrower but larger in spiders than in carabids. At the boundary between two more similar habitats (grazed and ungrazed upland grassland) the edge effect was much reduced, species richness was not elevated, and the level of overlap between habitats was much wider. Edge permeability, structural similarity and altitude were considered the most important factors for the differences between boundaries studied. It is inferred that in the high altitude invertebrate community most species are widespread crossing boundaries between vegetation types regularly, though some species may have affinities to particular habitats for different aspects of their ecology. The implications that this study has for understanding the effects and impacts of habitat heterogeneity at the landscape level are discussed, such as invertebrate movement patterns, population dynamics and management aspects.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1988. / Vita. Abstract. Includes bibliographical references (leaves 79-84). Also available via the Internet.

Thesis (M.S.)--Villanova University, 2009. / Biology Dept. Includes bibliographical references.

Thesis (M.S.)--Villanova University, 2009. / Biology Dept. Includes bibliographical references.

Proefschrift--Utrecht. / "Stellingen" ([3] p.) laid in.