Sociable widow spiders? Evidence of subsociality in Latrodectus Walckenaer, 1805 (Araneae, Theridiidae)

A first case of subsociality is reported for the genus Latrodectus. Individuals were found sharing the same web and feeding together. In captivity they showed mutual tolerance and communal feeding. This finding is remarkable for two reasons. First, widow spiders, even compared with other spiders, are famously aggressive and cannibalistic so that social behavior in the genus was unexpected. Second, the genus nests outside the ""Anelosimus + lost colulus"" clade where all the other social theridiids are found.

Brown recluse and black widow spiders.

"09/07"--Colophon.

Envenomation caused by Latrodectus geometricus in São Paulo state, Brazil: a case report

Widow spiders (Latrodectus spp.), also known as "black widows", have a worldwide distribution and can cause latrodectism. To the best of our knowledge, in Brazil, only one case of Latrodectus geometricus (Koch, 1841) envenomation in a human has been reported. The aim of the present report is to describe a spider bite caused by Latrodectus geometricus in a patient who lives in Paranapanema, São Paulo state, Brazil.

Perception of ultraviolet light by crab spiders and its role in selection of hunting sites

The perception of ultraviolet (UV) light by spiders has so far been only demonstrated in salticids. Crab spiders (Thomisidae) hunt mostly on flowers and need to find appropriate hunting sites. Previous studies have shown that some crab spiders that reflect UV light use UV contrast to enhance prey capture. The high UV contrast can be obtained either by modulation of body colouration or active selection of appropriate backgrounds for foraging. We show that crab spiders (Thomisus sp.)hunting on Spathiphyllum plants use chromatic contrast, especially UV contrast, to make themselves attractive to hymenopteran prey. Apart from that, they are able to achieve high UV contrast by active selection of non-UV reflecting surfaces when given a choice of UV-reflecting and non-UV reflecting surfaces in the absence of odour cues. Honeybees (Apis cerana) approached Spathiphyllum plants bearing crab spiders on which the spiders were high UV-contrast targets with greater frequency than those plants on which the UV-contrast of the spiders was low. Thus, crab spiders can perceive UV and may use it to choose appropriate backgrounds to enhance prey capture, by exploiting the attraction of prey such as honeybees to UV.

Identification of insects, spiders and mites in vegetable crops. Workshop Manual, 2nd edition

Accurate and confident identification of the insects, spiders and mites in vegetable crops is the first step towards successful management of pests and natural enemies. It is an essential prerequisite for crop monitoring, which is the backbone of an effective pest management program. This workshop manual and trainer's handbook were compiled as part of an insect, spider and mite identification program for Australian vegetable growers. The workshop training is designed to help growers to: • know how to collect and preserve insects for identification • be able to classify most common insects (particularly those of horticultural significance) into broad groups • appreciate the importance of these groups in pest, predator and parasite identification and management • collect and classify some insect pests, predators and parasites of horticultural importance.

Identification of insects, spiders and mites in vegetable crops: Trainer's handbook

The trainers manual provides workshop plans and sample slides for trainers wishing to conduct the 'Identification of insects, spiders and mites in vegetable crops' workshop.

The role of spiders as predators of two lepidopteran Brassica pests

Spiders are thought to play a significant role in limiting pest outbreaks in agroecosystems such as vineyards, orchards and cotton. The diversity and impact of spiders in vegetable crops are less well understood, although there is evidence that predators may be important for suppression of lepidopteran pests in Brassica crops, particularly early in the season before parasitoids become established. Sampling was conducted in early season plantings of Brassicas in the Lockyer Valley (South East Queensland, Australia) in order to determine the most commonly occurring spider families. The most numerous were Theridiidae, which were more strongly associated with cauliflower and poorly associated with cabbage. The Lycosidae and Clubionidae/Miturgidae (formerly in the ‘catch-all’ family Clubionidae) also occurred commonly. Lycosidae (and to a lesser extent Salticidae) had above average abundance in Chinese cabbage and below average abundance in broccoli compared with average abundance for these spider families; Clubionidae/Miturgidae had above average abundance in cauliflower. Laboratory studies were then conducted to explore the predatory capacity of these three most commonly occurring spider families. All three were capable of feeding on larvae of the diamondback moth, Plutella xylostella (Linnaeus), and cabbage cluster caterpillar, Crocidolomia pavonana (Fabricius), under laboratory conditions. Theridiidae, which are thought to prey on small pests such as leafhoppers and aphids, were able to successfully attack larvae up to five times their body size. Predation rates varied from an average of 1.7 (SE = 0.47) (1.6 control corrected) larvae consumed over a 24 h period in the case of the Theridiidae, to 3.3 (SE = 0.60) larvae for the Clubionidae/Miturgidae.

Short-term effects of variable retention on epigaeic spiders and carabid beetles in Finland

Forestry has influenced forest dwelling organisms for centuries in Fennoscandia. For example, in Finland ca. 30% of the threatened species are threatened because of forestry. Nowadays forest management recommendations include practices aimed at maintaining biodiversity in harvesting, such as green-tree retention. However, the effects of these practices have been little studied. In variable retention, different numbers of trees are retained, varying from green-tree retention (at least a few live standing trees in clear-cuts) to thinning (only individual trees removed). I examined the responses of ground-dwelling spiders and carabid beetles to green-tree retention (with small and large tree groups), gap felling and thinning aimed at an uneven age structure of trees. The impacts of these harvesting methods were compared to those of clear-cutting and uncut controls. I aimed to test the hypothesis that retaining more trees positively affects populations of those species of spiders and carabids that were present before harvesting. The data come from two studies. First, spiders were collected with pitfall traps in south-central Finland in 1995 (pre-treatment) and 1998 (after-treatment) in order to examine the effects of clear-cutting, green-tree retention (with 0.01-0.02-ha sized tree groups), gap felling (with three 0.16-ha sized openings in a 1-ha stand), thinning aiming at an uneven age structure of trees and uncut control. Second, spiders and carabids were caught with pitfall traps in eastern Finland in 1998-2001 (pre-treatment and three post-treatment years) in eleven 0.09-0.55-ha sized retention-tree groups and clear-cuts adjacent to them. Original spider and carabid assemblages were better maintained after harvests that retained more trees. Thinning maintained forest spiders well. However, gap felling and large retention-tree groups maintained some forest spider and carabid species in the short-term, but negatively affected some species over time. However, use of small retention-tree groups was associated with negative effects on forest spider populations. Studies are needed on the long-term effects of variable retention on terrestrial invertebrates; especially those directed at defining appropriate retention patch size and on the importance of structural diversity provided by variable retention for invertebrate populations. However, the aims of variable retention should be specified first. For example, are retention-tree groups planned to constitute life-boats , stepping-stones or to create structural diversity? Does it suffice that some species are maintained, or do we want to preserve the most sensitive ones, and how are these best defined? Moreover, the ecological benefits and economic costs of modified logging methods should be compared to other approaches aimed at maintaining biodiversity.

Widow rockfish: Proceedings of a workshop, Tiburon, California, December 11-12, 1980

This workshop was organized because of the increase between 1978 and 1980 in coastwide landings of widow rockfish, from less than 1,000 mt to more than 20,000 mt, and because of scientists' concern with the lack of knowledge both of the fishery and biology of the species. Most scientists active in research on Pacific groundfish, as well as some members of the fishing industry and fishery managers, attended the workshop. These proceedings contain the report of the workshop discussion panel, status reports on California, Oregon, and Washington fisheries through 1980, and a collection of seven papers presented at the workshop. The status reports provide an historical perspective of the development of an important fishery. The papers present a fairly complete survey of biological knowledge of widow rockfish, economic status of the fishery, and fishery-independent methods for estimation of abundance. The papers also contain some information developed after the workshop. Since the workshop, the fishery has matured. Largest landings were made in 1981, when more than 28,000 mt were landed. Maximum sustainable yield (MSY) is estimated to be slightly less than 10,000 mt, and the stock appeared to be at about the MSY level in 1985. The Pacific Fishery Management Council and National Marine Fisheries Service have implemented regulations that have maintained landings since 1983 at approximately the maximum sustainable yield level. Fishery-dependent stock assessments are being made on an annual basis for the Pacific Fishery Management Council. While these assessments are considered to be the best possible with available data, scientists responsible for the assessment have chosen to delay their publication in the formal scientific literature until more data are obtained. However, the stock assessment reports are available from the Pacific Fishery Management Council. In addition to the papers in this collection, three papers have been published on widow rockfish since 1980. BoehIert, Barss, and Lamberson (1982) estimate fecundity of the species off Oregon; Gunderson (1984) describes the fishery and management actions; and Laroche and Richardson (1981) describe the morphology and distribution of juvenile widow rockfish off Oregon. During the past decade, the fishery for widow rockfish has developed from a minor fishery to one of the more important on the Pacific Coast. Our knowledge of the biology and dynamics of the species has progressed from minimal to relatively extensive for a groundfish species. It is our intention in preparing this collection of papers to make this knowledge readily available to the scientific community. (PDF file contains 63 pages.)

A dragline-forming mobile robot inspired by spiders.

Mobility of wheeled or legged machines can be significantly increased if they are able to move from a solid surface into a three-dimensional space. Although that may be achieved by addition of flying mechanisms, the payload fraction will be the limiting factor in such hybrid mobile machines for many applications. Inspired by spiders producing draglines to assist locomotion, the paper proposes an alternative mobile technology where a robot achieves locomotion from a solid surface into a free space. The technology resembles the dragline production pathway in spiders to a technically feasible degree and enables robots to move with thermoplastic spinning of draglines. As an implementation, a mobile robot has been prototyped with thermoplastic adhesives as source material of the draglines. Experimental results show that a dragline diameter range of 1.17-5.27 mm was achievable by the 185 g mobile robot in descending locomotion from the solid surface of a hanging structure with a power consumption of 4.8 W and an average speed of 5.13 cm min(-1). With an open-loop controller consisting of sequences of discrete events, the robot has demonstrated repeatable dragline formation with a relative deviation within -4% and a length close to the metre scale.

Sexual size dimorphism and reproductive investment by female spiders: A comparative analysis

We investigate the association between female reproductive investment, absolute size, and sexual size dimorphism in spiders to test the predictions of the fecundity-advantage hypothesis. The relationships between absolute size and sexual size dimorphism and aspects of female reproductive output are examined in comparative analyses using phylogenetically independent contrasts. We provide support for the idea that allometry for sexual dimorphism is the result of variation in female size more so than male size. Regression analyses suggest selection for increased fecundity in females. We argue that fecundity selection provides the only general explanation for the evolution of sexual size dimorphism in spiders.