Spider (Araneae) Species Composition and Seasonal Abundance in San Joaquin Valley Grape Vineyards

As part of an investigation to estimate the effect of resident spider populations on Erythroneura variabilis Beamer, spider species composition, relative abundance, and seasonal occurrence were determined. Spiders were sampled monthly during the 1992 and 1993 growing seasons; their numbers were pooled and analyzed for species diversity using the Renkonen index of similarity and cluster analysis. Twenty-seven species of spiders were recorded, representing 14 families. The most common species were Cheiracanthium inclusum (Hentz), Trachelas pacificus (Chamberlin and Ivie), Theridion dilutum Levi, Theridion melanurum Hahn, Oxyopes scalaris Hentz, Oxyopes salticus Hentz, Hololena nedra Chamberlin and Ivie, and Metaphidippus vitis (Cockerell). Three species (C. inclusum, T. dilutum, and T. melanurum) constituted \u3e30% of all spiders collected; however, species diversity varied among vineyard sites. In 4 vineyard sites, hunting spiders (C. inclusum, T. pacificus, Oxyopes spp., and M. vitis) dominated the fauna, representing an average of 79.7% of the specimens collected. In the other 3 vineyards, hunting and web-weaving spiders were more equally represented, averaging 43.5 and 50.0%, respectively,of all spiders collected. Species similarity between vineyards from both years ranged from 19 to 73% based on the Renkonen index. Similarly, cluster analysis showed a wide separation in species composition among sampled vineyards. The discrepancy in species similarity among sampled vineyards is discussed in reference to potential prey density and vineyard cultural practices. Seasonal abundance patterns of the 8 most common species are presented and discussed in reference to their respective phenologies

Influence of Ground Cover on Spider Populations in a Table Grape Vineyard

1. Cover crops and/or resident ground vegetation have been used in California vineyards to increase the number of predators and decrease the number of pestiferous herbivores. The most common resident predators in vineyards are spiders (Araneae). Several observational studies suggest that the addition of cover crops results in an increase in spider density and a decrease in insect pest densities. 2. To test experimentally the effects of cover crops and/or resident ground vegetation (hereafter collectively referred to as ground cover) on spider populations, a 3-year study was undertaken in a commercial vineyard. Large, replicated plots were established with and without ground cover during the growing season. Spider species diversity was analysed on the vines and on the ground cover. 3. On the vines, there was no significant difference in spider species richness or the total number of spiders in plots with and without ground cover. There were differences in the relative abundance of two spiders between treatments, with one species (Trachelas pacificus [Chamberlin & Ivie]) more abundant in plots with ground cover and another (Hololena nedra Chamberlin & Ivie) more common on vines in plots with no ground cover. Annual variation in spider abundance was greater than variation due to ground cover treatment. 4. On the ground cover, the spider species diversity was considerably different from that found on the vines above, suggesting that there is little movement of spiders between the ground cover and the vines. Enhancement of T. pacificus populations on vines with ground covers may be a result of prey species movement between the ground cover and the vines. Spider abundance was sparse on the bare ground. 5. The maintenance of ground cover increased spider species diversity in the vineyard as a whole (vine and ground cover). However, the relatively small changes in spider abundance on the vines indicate there are limitations in the use of ground covers for pest management with respect to generalist predators

Can Cover Crops Reduce Leafhopper Abundance in Vineyards?

In 3 of 4 vineyards we studied, late-season leafhopper density was lower on vines in cover cropped plots than in plots with no cover crops. However, the level of leafhopper reduction (about 15%) was rarely economically important and the mechanisms leading to reduction were not clear. For example, there were few differences in the number of leaf hopper predators or parasitoids on the vines in cover cropped versus no cover plots. However, there were significant between-treatment differences in vine growth. Plots with seasonwide maintenance of a cover crop and resident grasses had a reduction in vine vigor. Lower vine vigor has been associated with lower leafhopper densities and, in our studies conducted from 1993 to 1996, those plots with reduced vine vigor often had the greatest reduction in late-season leafhopper density

Explorations in the Measurement of Empathy As Analytical Predictive Ability

This was a preliminary effort to develop a scale for the measurement of empathy as analytical predictive ability. The approach embodied the use of 20 words in three contexts; the 60 rating elements comprised the scale. Extent of agreement between self ratings of a person to be judged (reader) and the estimates of those ratings by a group of persons (judges) was used as a measure of empathic ability. An attempt to take into account possible spurious influences on the empathy scores was not fruitful. The standard materials, including a filmed version of the reader\u27s behavior, were used with several samples. Results showed generally better than chance empathy scores. There was some intimation that this type of scale is useful in identifying students for a school of nursing. Other between-group differences are suggested. The findings for a group of student teachers were not revealing

Studies on the preparation, properties and analysis of high purity yttrium oxide and yttrium metal at the Ames Laboratory

The research and development work carried out at the Ames Laboratory on the chemistry and metallurgy of yttrium is described in detail in this report or companion reports to which references are herein made. Discussions of the separation of yttrium from the rare-earth elements by ion exchange, of comprehensive investigations of the preparation of yttrium fluoride, and of various ways of reducing the fluoride to the metallic state are presented. Chemical and spectrographic methods of analyzing yttrium and its compounds for oxygen and other impurities are described and comparisons made between the different methods. A pilot plant process for producing tonnage quantities of yttrium metal is presented with detailed descriptions of the equipment and operating procedures employed. The complete process entails the extraction of an yttrium and rare earth mixture from xenotime sand, separation of the yttrium from this mixture in thirty-inch-diameter columns, hydrofluorination of the resulting oxide and its subsequent reduction to the metal. The basic metal process consists of the reduction of yttrium fluoride with calcium, forming a low melting yttrium-magnesium alloy. The magnesium is subsequently removed by vacuum sublimation, producing a porous yttrium product. This is consolidated by vacuum arc melting into a six-inch-diameter ingot. Quantities of high purity yttrium metal were prepared by vacuum distillation and by-a sa,lt extraction refining process. Yttrium metal containing 100 to 300 ppm oxygen is soft, ductile and easily fabricated at room temperature