<Emphasis Type="Italic">Argiope bruennichi</Emphasis> shows a drinking-like behaviour in web hub decorations (Araneae,Araneidae)

As stationary predators, araneid spiders that lack protective retreats are especially vulnerable to abiotic influences. Species of the genus Argiope permanently remain at the hub of their orb webs and are thereby exposed to desiccating circumstances. Like other land arthropods, spiders must balance their hygric status. Beside desiccation avoidance behaviours, they can manage this balance by water gain through either liquefied prey items or direct ingestions of free water. Drinking-like behaviours are sparely documented for Araneids. We observed Argiope bruennichi ingesting accumulated water droplets from the silk-overstitched web hub, a part of the web decoration, and subsequently tested whether this behaviour is a regular feature of this species. In 50% of our observations, spiders that had been sprayed with water actively searched the hub decoration for water droplets and ingested them. The behavioural elements were very stereotypic among the tested individuals. Significantly, A. bruennichi females only searched the covered web hubs for water, even though the entire web was moistened. These data suggest that hub decorations of A. bruennichi might have an adaptive significance by helping to maintain a balance of water metabolism, adding yet another element to the spirited debate about the functional significance of web decorations.     

园蛛总科网型不同的蜘蛛间分子系统发生关系的初步探讨

为初步探讨园蛛总科内网型不同的蜘蛛间分子系统发生关系,测定了9种蜘蛛核18S rRNA基因的部分序列。联合GenBank中的2种蜘蛛18S rRNA基因序列数据,用NJ法、MP法和ML法重建分子系统树,结果表明：（1）织圆网的园蛛科和肖蛸科蜘蛛在园蛛总科中不是姊妹群;（2）不织圆网的球蛛科和皿蛛科也不是单系发生,证实了皿蛛片网和球蛛网独立起源的观点;（3）皿蛛科蜘蛛的分子系统发生地位与肖蛸科较近、而与园蛛科较远,这表明皿蛛科和园蛛科问雄性触肢结构的相似性很可能是类似而不是同源相似。     

Foraging behavior of the communal spider,Philoponella republicana (Araneae: Uloboridae)

The communal orb-weaving spider, Philoponella republicana,was observed in the subtropical moist forest of Southeast Peru. These spiders live in colonies of conspecifics whose individual orbs are connected by silk. The wrapping of a prey prior to feeding is a large component of the prey capture process because P. republicanahas no venom with which to kill an insect. Wrapping time was the only aspect of prey capture that was strongly correlated with the size of the insect captured. Occasionally we observed several individuals working together to wrap a prey item. These joint efforts were more frequent on prey larger than the capturing spider. Although group captures accounted for only 5.5% of captures, they represented 14.7% of the biomass obtained. A comparison of the relationship between wrapping time and prey size for solitary and group efforts suggested that, by working together, the spiders reduced their total handling time. In most cases only one spider fed on the captured prey.     

Variation in foraging investment during the intermolt interval and before egg-laying in the spiderNephila clavipes (Araneae: Araneidae)

Repeated observations were made of marked, freeliving females in three disjunct populations of the orb-weaving spider Nephila clavipes,recording orb size and structure and barrier web complexity. These longitudinal studies revealed regular patterns of variation in orb size associated with the molting cycle and cycle of egg maturation. Juveniles maintained in an insectary under a controlled feeding regime exhibited similar variation in orb size. All spiders ceased orb renewal prior to molting and the majority replaced the viscid orb with a nonviscid platform prior to molting. Differences among the populations in molting web structure are discussed in light of differences in the physical and biological environments. Cessation of orb renewal corresponded temporally with reported physiological changes associated with the molt cycle and possibly reflect changes in resource partitioning between growth and foraging during the molt cycle.     

Foraging success of largemouth bass at different light intensities: implications for time and depth of feeding

Laboratory feeding trials were conducted to determine how light intensity affects foraging success by the visual piscivore, the largemouth bass ( Micropterus salmoides ). Foraging success was greater than 95% at light levels ranging from low intensity daylight (2.43 × 10² lx) to moonlight (3 × 10⁻³ lx), but declined significantly to 62% at starlight (2 × 10⁻⁴ lx) and near 0% in total darkness. Over a range of low to high water clarities (0.5, 2.0, and 4.0 m Secchi depth), estimated depth limits for feeding during the day ranged between 5.5 to 44 m and from 1.6 to 13 m at night during a full moon. At starlight, light intensity rapidly attenuated to a level below the feeding threshold within 0.5 m of the surface at all water clarities. The depth of the water column available for feeding in low clarity water (0.5 m Secchi) was 67 and 75% less than at moderate (2.0 m Secchi) and high (4.0 m Secchi) water clarities. The findings illustrate how differences in the light environment can have important ramifications for predator-prey interactions.     

Competition between introduced and native spiders (Araneae: Linyphiidae)

The European sheet-web spider Linyphia triangularis (Araneae: Linyphiidae) has become established in Maine, where it often reaches very high densities. Two lines of evidence from previous work suggest that L. triangularis affects populations of the native linyphiid spider Frontinella communis. First, F. communis individuals are relatively scarce in both forest and coastal habitat where L. triangularis is common, but more common where L. triangularis is at low density. Second, in field experiments, F. communis species are less likely to settle in experimental plots when L. triangularis is present, and F. communis disappears from study plots when L. triangularis is introduced. Here we test two mechanisms that may underlie these patterns. First, we tested whether L. triangularis invades and usurps the webs of F. communis. When spiders were released onto webs of heterospecifics, L. triangularis was more likely to take over or share webs of F. communis than the reverse. We also observed natural takeovers of F. communis webs. Second, we explored the hypothesis that L. triangularis reduces prey availability for native species. We sampled flying prey in areas with L. triangularis and those where it had been removed, and found no effect of spider presence on measured prey density. We also found no effect of prey supplementation on web tenacity in F. communis, suggesting that F. communis movements are not highly dependent on prey availability. We conclude that web takeover is likely more important than prey reduction in driving negative effects of L. triangularis on F. communis.     

The protective function of the compact silk nest of social Stegodyphus spiders (Araneae,Eresidae)

Summary This study investigates the suggested protective function of the compact silken nest of two species of social Stegodyphus spiders (S. dumicola and S. mimosarum), as a possible ultimate factor for their sociogenesis. Being inhabitants of African dry thornbush country, these spiders are endangered by overheating and desiccation. In the laboratory, both species were found to avoid temperatures >40° C. In the field, temperature in the nest between 7:00 and 21:00 h tends to be higher than air-temperature outside, and between 13:00 and 15:00 h even tends to exceed 40° C. The nest thus is of no value in temperature regulation. Nor is it effective in protecting the spiders from desiccation: Both species have a body water content of 65.2±3.8% and are extremely desiccation resistant; they survived 9 days at 37°C in an exciccator with P₂O₅, with a daily average % liveweight reduction of 4.94(±1.1). In the field, relative humidity inside the nest between 11:00 and 19:00 h tends to be lower than that of the air outside. Inspection of burnt areas showed that the nest does not protect the spiders from bushfire. The nest does protect from wind, hail, and direct sun-radiation; but available natural retreats, or a simple silken shield, or the funnel-shaped silk tube inhabited by solitary Stegodyphus, have the same effect.     

Sexual cannibalism and sperm competition in the golden orb-web spider Nephila plumipes (Araneoidea): female and male perspectives

Mating systems are frequently shaped by conflicts over reproductive interests between males and females. Sexual cannibalism canbe an especially dramatic manifestation of such conflicts.However, the resolutions of this conflict differ among sexuallycannibalistic spider species. Cannibalism may be in the interestof both sexes when females consume males as a foraging decisionto improve fecundity and/or males sacrifice their bodies toincrease fertilization success. In other species, females exertsequential choice of partner by selectively terminating copulationthrough cannibalism while males fail to obtain a paternityadvantage. Here, we investigate the adaptive value of cannibalismin the orb-web spider Nephila plumipes where 60% of males donot survive copulation. Virgin females in poor condition aremore frequently cannibalistic and more likely to kill largemales, but the frequency of cannibalism among mated femalesis not influenced by these factors. Instead, males that matewith mated females increase their fertilization success bybeing cannibalized. Cannibalized males generally mate for longer,but longer copulations correspond with increased paternity onlyin mated females. The amount of sperm from particular malesthat a female stored was not influenced by any of the measuredvariables. The number of sperm stored was not related to paternity,nor was there any detectable reduction in sperm number afterfemales had reproduced. Our data suggest that the conflict between the sexes differs between virgin and mated females.Females should always cannibalize a male, but males only gainfrom cannibalism when mating with mated females, not when matingwith virgin females. Interestingly, the frequencies of cannibalismare not different in matings with virgin or mated females.     

Sociality in a bark-dwelling huntsman spider from Australia,Delena cancerides Walckenaer (Araneae: Sparassidae)

Summary Social behavior is reported for the first time in a member of the family Sparassidae (Araneae), the Australian huntsman spiderDelena cancerides Walckenaer. Unlike any previously known social spider, this is a bark dwelling species and, thus, its sociality cannot have its basis on an aerial web, the structure that has been considered central to the evolution of sociality in other spider species. Colonies ofD. cancerides may comprise up to 300 individuals living in close physical contact under the exfoliating bark of deadAcacia, Callitris andCasuarina species. Specimens maintained in the laboratory feed communally and capture prey jointly. Although this intranest tolerance and communal feeding behavior is reminiscent of other highly social spiders,D. cancerides notably differs from these other species in the extreme aggression shown towards members of foreign colonies, its outbred population structure, and lack of sex ratio bias. We suggest that sociality in this species may have been facilitated by the presence of extended maternal care in the ancestral phylogenetic lineage, as suggested by the occurrence of such behavior in related nonsocial species, and that colonial living may have arisen as a consequence of the reduction and fragmentation ofDelena's habitat associated with the rise to dominance of the eucalypts. The apparent colony recognition observed may have evolved becauseDelena's hunting habits may require mechanisms to locate one's own colony after foraging expeditions and to exclude wandering outsiders from entering one's nest, in contrast to web-bound species that do not need to leave their nest to forage. How the observed outbreeding is accomplished in the face ofDelena's extreme intolerance to members of other nests, as well as how new colonies are formed, are issues that have yet to be investigated.     

Behavioural evidence of UV sensitivity in jumping spiders (Araneae: Salticidae)

Jumping spiders are known to possess ultraviolet (UV) receptors in the retinas of their large-principal eyes. The existence of UV visual cells, however, does not prove that jumping spiders can see into the UV part of spectrum (300–400 nm) or whether such an ability plays any role in salticid intra-specific interactions. In the study reported herein, we performed behavioural experiments to test whether a UV−reflecting jumping spider, Cosmophasis umbratica, is sensitive to UV wavelengths and whether UV cues are important in intra-specific communication. The absence of UV cues not only affected intra-specific behaviour by significantly reducing the frequency of agonistic displays, but also elicited unprecedented courtship displays in males towards their own mirror images and conspecific opponents. Furthermore, C. umbratica males were able to respond rapidly to changes in UV cues of conspecific mirror images by switching between agonistic and courtship displays. These findings clearly demonstrate that C. umbratica males are capable of seeing UV wavelengths and that UV cues are necessary and sufficient for this species to enable the agonistic displays. Hence, UV light may have an important role to play in intra-specific communication in jumping spiders.     

Foraging strategies as a function of season and rank among wild female chimpanzees (Pan troglodytes)

Among mammals, female reproduction is generally thought to befood limited, and dominance should theoretically afford high-rankingfemales with access to better food resources. Although the importanceof dominance rank among female chimpanzees (Pan troglodytes)has been debated in the past, mounting evidence suggests thatrank is very important among females (P. t. schweinfurthii)at Gombe National Park, Tanzania. In this study, we investigatedthe influence of season and dominance rank on female foragingstrategies. We found that high-ranking females spent less timeforaging and tended to have a narrower diet breadth and higherdiet quality than subordinate females. In this way, subordinatefemale foraging strategies were consistent with how femalesin general adapted to periods of food scarcity. The resultsof this study therefore suggest that low-ranking females mayface persistent "food scarcity" as a result of interferencefood competition. We also provide evidence that subordinatesmay forage less efficiently because they occupy lower qualityhabitats or avoid associating with dominant females in sharedareas.     

Social behaviour of spitting spiders (Araneae: Scytodidae) from Singapore

The social organization of Scytodes sp., a spitting spider from Singapore, was investigated in the field and in the laboratory. The characteristics considered were colony structure, maternal care, prey capture, prey sharing, adults provisioning with prey and how feeding regime influences the level of tolerance expressed by juveniles that were living together. The characteristics of this species were compared with those of other Scytodes species that have been studied previously. Based on our findings, we conclude that in this species, social organization is 'periodic-social', with extended maternal care, this being a type of 'subsociality'. The females of Scytodes sp. wrapped their eggs in a silk egg sac and used their chelicerae to hold the eggs until they hatched. Spiderlings tended to remain in their mother's web until the fourth instar (i.e. after the third moult) but they were also highly aggressive and cannibalistic towards conspecifics after the third instar. Females carried prey to their spiderlings and either fed alongside the brood or left them to feed alone. Spiderlings also captured large prey cooperatively by spitting onto, biting and feeding on it together. The occurrence of cannibalism among her juveniles did not appear to be influenced by whether the adult female was present or not, nor did it appear to be influenced by prey abundance.     

A survey of running crab spiders (Araneae: Philodromidae) in Iran

Nine species and four genera of Philodromidae are identified and recorded from various parts of Iran including Pulchellodromus medius (O. Pickard-Cambridge, 1872) (genus and species new to Iran) and Thanatus setiger (O. Pickard-Cambridge, 1872) (new to Iran). The male of Rhysodromus hierosolymitanus (Levy, 1977), which was previously known only from females, is described and diagnosed here.     

Foraging strategies of yakushima macaques (Macaca fuscata yakui )

I investigated the activity budget and diet of Yakushima macaques (Macaca fuscata yakui,)in warm temperate broad- leaved forest of Yakushima, Japan. Both time spent feeding and time spent moving varied considerably between half- months. However, total time spent in active behaviors— feeding time plus moving time— was stable. The composition of the diet also showed considerable variation between half- months. The macaques fed mainly on fruits, seeds,mature leaves, fallen seeds, flowers, and young leaves, each of which accounted for more than 30% of feeding time in at least 1 half- month. They also ate insects and fungi, but each of them comprised ≤ 25 and ≤ 8% of feeding time in any half- month, respectively. Time spent feeding on mature leaves, young leaves, flowers, or fallen seeds is positively correlated with total time feeding and is negatively correlated with time moving. In contrast, time feeding on fruits, seeds, insects or fungi is negatively correlated with time feeding and is positively correlated with time moving. Foraging on foods that have a low energy content, a high density, and a relatively even distribution— mature leaves— or that need much manipulation to be processed— flowers and fallen seeds— increased feeding time, while foraging on foods for which monkeys must search intensively in the forest— fruits, seeds, insects, and fungi— led to increased moving time. I examined foraging strategies of Yakushima macaques in terms of moving costs and the quality of food items. Regarding time feeding on fruits, which have more energy and may need less manipulation than other foods, as a benefit, and moving time as a cost, they seemed to employ a strategy that balanced the costs and benefits of foraging.