Investigation of two new putative pheromone components of the invasive Australian redback spider,Latrodectus hasseltii,with potential applications for control

The Australian redback spider, Latrodectus hasseltii preys on at least 10 endemic species in New Zealand, highlighting a need for control. Male redbacks are attracted to virgin females by an airborne pheromone. The aim of this study was to analyse the response of male redback spiders to two volatile chemicals found on the silk of virgin but not mated females, to determine whether these compounds constitute components of the airborne pheromone. Mature male redback spiders were placed in an olfactometer where they had a choice of two stimuli. We compared their response to paired combinations of a control, virgin silk, butyric acid and isovaleric acid. Male redbacks responded equally strongly to butyric acid and virgin silk, in terms of time spent near the stimulus. The identification of butyric acid as a component of the airborne sex pheromone of L. hasseltii provides the groundwork for developing a pheromone-based control.     

Gustatory thresholds for food-associated sugars in the spider monkey (Ateles geoffroyi)

The purpose of this study was to determine gustatory thresholds for five different food-associated sugars in Ateles geoffroyi. Using a two-bottle test, three adult spider monkeys were found to significantly prefer concentrations as low as 3 mM sucrose, 15 mM fructose, 20 mM glucose, and 10 mM lactose over tap water. Maltose was significantly discriminated down to 20 mM with individual animals showing either a preference or an aversion, or an inverted U-shaped function of preference toward higher concentrations of this carbohydrate. The results showed the spider monkey to respond to lower sugar concentrations compared to other nonhuman primates tested so far and thus support the assumptions that Ateles geoffroyi may use sweetness as a criterion for food selection, and that the remarkably high sweet-taste sensitivity of this frugivorous species might be correlated with its dietary specialization. © 1996 Wiley-Liss, Inc.     

Artificial selection for timing of dispersal in predatory mites yields lines that differ in prey exploitation strategies

Dispersal is the main determinant of the dynamics and persistence of predator–prey metapopulations. When defining dispersal as a predator exploitation strategy, theory predicts the existence of a continuum of strategies: from some dispersal throughout the predator–prey interaction (the Milker strategy) to dispersal only after the prey had been exterminated (the Killer strategy). These dispersal strategies relate to differences in prey exploitation at the population level, with more dispersal leading to longer predator–prey interaction times and higher cumulative numbers of dispersing predators. In the predatory mite Phytoseiulus persimilis, empirical studies have shown genetic variation for prey exploitation as well as for the timing of aerial dispersal in the presence of prey. Here, we test whether artificial selection for lines that differ in timing of dispersal also results in these lines differing in prey exploitation. Six rounds of selection for early or late dispersal resulted in predator lines displaying earlier or later dispersal. Moreover, it resulted—at the population level—in predicted differences in the local predator–prey interaction time and in the cumulative numbers of dispersers in a population dynamics experiment. We pose that timing of dispersal is a heritable trait that can be selected in P. persimilis, which results in lines that show quantitative differences in local predator–prey dynamics. This opens ways to experimentally investigate the evolution of alternative prey exploitation strategies and to select for predator strains with prey exploitation strategies resulting in better biological control.     

Effect of architectural angularity on refugia selection by the brown spider,Loxosceles gaucho

Some brown spider species infest man‐made environments and pose a threat to human health. Because habitat architecture affects spider populations, I evaluated the preferences of individuals of Loxosceles gaucho (Gertsch) (Araneae: Sicariidae) for refugia with different angular structures. Four differently angled refugia models (acute‐, right‐, obtuse‐angled and cylindrical) were placed on the litter of a forest fragment and observed each month for 1 year. Females of this species were found to prefer refugia with acute angles. This finding brings new information to our understanding of brown spider infestations in man‐made environments: refugia with acute angles are likely to offer more protection for females and their offspring.     

中国红螯蛛属两新种及两种雄蛛新发现(蜘蛛目:管巢蛛科)

本文记述红螯蛛属２新种,即宁明红螯蛛Ｃｈｅｉｒａｃａｎｔｈｉｕｍｎｉｎｇｍｉｎｇｅｎｓｉｓ,ｓｐ．ｎｏｖ,和思茅红螯蛛Ｃｈｅｉｒａｃａｎｔｈｉｕｍｓｉｍａｏｅｎｓｉｓ,ｓｐ．ｎｏｖ及２种雄性的补充描述,即粗美红螯蛛ＣｈｅｉｒａｃａｎｔｈｉｕｍｅｘｑｕｅｓｔｉｕｍＺｈａｎｇｅｔＺｈｕ,１９９３和纤红螯蛛ＣｈｅｉｒａｃａｎｔｈｉｕｍｆｉｂｒｏｓｕｍＺｈａｎｇｅｔａｌ,１９９４模式标本保存于湖南省生物研     

Do stabilimenta in orb webs attract prey or defend spiders?

Orb-weaving spiders are ideal organisms for the study of conflictbetween behavioral investments in foraging and defense becausetheir webs provide physical manifestations of those investments.We examined the impact of including stabilimenta, designs ofbright-white noncapture silk, at the center of orb webs forforaging and defense in Argiope aurantia. Our findings suggestthat stabilimentum building is a defensive behavior, supportingthe "web advertisement" hypothesis that the high visibilityof stabilimenta can prevent birds from flying through webs.Yet, spiders often do not include stabilimenta in their webs,indicating that a serious cost is associated with them. We alsoshow, through comparison of paired webs with and without stabilimenta,that stabilimenta reduce the prey capture success of spidersby almost 30%. This demonstrates the potential impact that defensivebehaviors of spiders can have on their foraging success andsuggests that much of the variation in stabilimenta may be accountedfor by a cost—benefit trade-off made when including stabilimentain webs.     

Draglines and Assessment of Fighting Ability in Cannibalistic Jumping Spiders

The frequency of injury and death during female-female aggression varies in the jumping spider genus Portia, with interactions being more violent (likely to end in death or injury of one of the combatants) in P. labiata (from Sri Lanka) than in another two species (P. fimbriata from Australia and P. schultzi from Kenya). To investigate the role of draglines in the assessment of fighting ability, two types of tests were carried out: 1) dragline discrimination and 2) mirror image response (Portia's reaction to mirror images is comparable to interaction with conspecific rivals). For both types of testing, triplets of equal-size conspecific females were used: one female (the test spider) was exposed to draglines of two equal-size conspecific females they had not encountered before (donor spiders). The fighting abilities of donor spiders were determined directly by staging intraspecific contests between them. In dragline-discrimination tests (spider placed in petri dish containing draglines from two conspecific females with different fighting ability), females of P. labiata, but not the other two species, avoided draglines of the superior fighter (i.e., they spent the majority of their time on draglines of donor spiders with lesser fighting ability). For mirror-image testing, the test spider was placed in a petri dish containing a mirror and draglines. Each test spider was tested on two successive days, with donor draglines in the two tests coming from conspecific females with different fighting ability. In these tests, females of P. labiata (but not the other two species) spent less time embracing (each spider pressing its forelegs, palps and front of body against the other spider) and more time in a part of the petri dish where view of the mirror was obstructed when on the draglines of donor spiders with greater fighting ability than when on the other conspecific's draglines. Findings from this study suggest that P. labiata females use signpost cues associated with draglines to assess the relative fighting abilities of unknown opponents.     

Determination of an Optimal Pitfall Trap Size for Sampling Spiders in a Western Australian Jarrah Forest

Pitfall trapping is a sampling technique extensively used to sample surface foraging invertebrates for biological diversity studies and ecological monitoring. To date, very few invertebrate studies have considered what trap size is optimal for sampling spiders. This study presents preliminary findings from a single short sampling period on the role of trap size in sampling spiders in a Western Australian Jarrah forest. Four different trap diameters (4.3, 7.0, 11.1 and 17.4 cm) were examined (4 trap sizes × 15 replicates = 60 traps). Two-way ANOVAs revealed no significant interaction effects between trap size or the spatial positioning of transects within the study site along which the pitfall traps were arranged. Post-hoc tests revealed abundance, family richness and species richness increased with increasing trap sizes for traps 7.0 cm. No significant differences in these dependent variables occurred between 4.3 and 7.0 cm traps, or for species richness between 11.1 and 17.4 cm traps. Determination of an optimal trap size was undertaken by bootstrapping and calculating species accumulation curves for increasing numbers of traps used. Three different criteria were considered: equivalent number of traps (15), standardized sampling intensity (cumulative trap circumference, approximately 207 cm) and standardized cumulative handling time (approximately 1 hour 17 minutes). The largest trap size (17.4 cm) was most efficient in terms of number of traps and trap circumference. For the same number of traps, it caught 19 species whereas all other trap sizes caught ten species. At the standardized circumference, it caught seven species whereas all other trap sizes caught five. For handling time, however, the two largest trap sizes (17.4 and 11.1 cm) were optimal. Both caught nine species whereas all other traps caught 相似文献   

Life table characteristics of Macrolophus caliginosus preying upon Tetranychus urticae

The life table characteristics of the polyphagous mirid Macrolophus caliginosus Wagner (Heteroptera: Miridae) preying on various stages of Tetranychus urticae Koch (Acari: Tetranychidae) with tomato as host plant were described at 22 °C. The following average parameters were obtained: Female longevity: 28.7 days; fecundity: 0.7 eggs/female/day; egg mortality: 2.6%; pre-oviposition period: 5.5 days; oviposition period: 18.1 days; post-oviposition period: 3.2 days; juvenile development time: 26.8 days; juvenile mortality: 34.9%; and sex ratio (/(+): 0.46. Life table parameters were estimated as net reproduction rate (R ₀): 6.15; intrinsic rate of increase (r _m): 0.031 day^–1; finite rate of increase (): 1.032; mean generation time (T _c): 58.17 days; and doubling time (T ₂) 22.2 days. The parameters obtained were in accordance with those reported for M. caliginosus fed on another mite species (T. turkestani Ugarov & Nikolski (Acari: Tetranychidae)). However, compared to the performance of M. caliginosus fed on common glasshouse insect pests, a diet consisting of only mites appeared to be inferior. However, being a voracious predator, M. caliginosus may be a valuable addition to existing methods of mite control.     

Food source of riparian spiders analyzed by using stable isotope ratios

We analyzed the food source of riparian spiders in a middle reach of the Chikuma River, Japan, by using stable isotope ratios of carbon and nitrogen. The carbon and nitrogen isotope ratios of attached algae were higher than those of terrestrial plants, reflecting a large carbon isotope fractionation in terrestrial plants and a difference in nitrogen sources. The carbon isotope ratios of terrestrial insects were similar to those of the terrestrial plants, and the ratios of aquatic insects were scattered between those of the terrestrial plants and the attached algae. The carbon and nitrogen isotope ratios of spiders were intermediate between those of the terrestrial and aquatic insects. The two-source mixing model using the carbon isotope ratio showed that the web-building spiders utilized both the terrestrial and aquatic insects, with large contribution by the aquatic insects (54% on average with a maximum of 92% among spiders taxa collected in each zone), in the riparian area in a middle reach of the Chikuma River. The large contribution of the aquatic insects was often observed for the spiders collected near river channel (<5m) and for the horizontal web-building spiders collected across the riparian area. The relative contribution of the aquatic insects might be related with food availability (distance from river channel) and spiders food preference reflected in their web types (horizontal vs. vertical). Our results showed that organic materials produced in the river channel, in the riparian area, and in the terrestrial area surrounding the riparian area were mixed at the carnivorous trophic level of riparian spiders.