About this species. Recorded altitude range 0m to m. Species text. Distribution The spider was first recorded in Britain in at Rye, East Sussex ( Locket. The orb-weaver genera Argiope, Gea, and Neogea from the western Pacific region (Araneae: Araneidae, Argiopinae). Bulletin of the Museum of Comparative . Description with pictures of the weaving of the cocoon and the laying of the eggs by the wasp spider, Argiope bruennichi.
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There are two major competing explanations for the counter-intuitive presence of bright coloration in certain orb-web spiders. Bright coloration could lure insect prey to the web vicinity, increasing the spider’s foraging success.
Alternatively, the markings could function as disruptive camouflage, making it difficult for the insect prey to distinguish spiders from background colour variation. We measured the prey capture rates of wasp spiders, Argiope bruennichithat were blacked out, shielded from view using a leaf fragment, or left naturally coloured.
Naturally coloured spiders caught over twice the number of prey as did either blacked-out or leaf-shielded spiders, and almost three times as many orthopteran prey. Spectrophotometer measurements suggest that the bright yellow bands on the spider’s abdomen are visible to insect prey, but not the banding on the legs, which could disguise the spider’s outline. Thus, our results provide strong support for the hypothesis that bright coloration in the wasp spider acts as a visual lure for insect prey and weak support for the hypothesis that the arrangement of the banding pattern across the spider’s body disguises the presence of the spider on the web.
The avoidance of recognition by potential prey is vital to the hunting success of sit-and-wait predators such as orb-web spiders Craig For example, among females of the genus Argiopeyellow and white stripes, bands and spots are common Levi Any potential benefit to females of using visual signals to attract males would appear to be outweighed by the cost of a lower prey capture rate, particularly as male Argiope locate females using long-range and contact pheromones Gaskett There is also a potential cost to spiders of increased visibility to their own predators.
There are, however, two ways by which bright coloration could increase prey capture rate and therefore be selectively advantageous. Many flying insects are attracted to the vibrant colours of flowers, and predators could take advantage of this.
Summary for Argiope bruennichi (Araneae)
For example, the Australian crab spider, Thomisus spectabilisclosely matches flower colour within the human visibility spectrum, but contrasts strongly under UV, which bees can also see. Studies have concluded that this UV colour contrast is a sensory trap that results in more frequent visits to flowers occupied by crab spiders Chittka ; Heiling et al.
Similarly, Tso et al. Also, experimentally obscuring the yellow or silver banding of the orchid spider Leucauge magnifica reduces the prey capture rates by up to three times compared with naturally coloured controls Tso et al. However, an alternative explanation is that bright coloration is a form of disruptive camouflage. Under this interpretation, obscuring bright colours would cause spiders to be more visible as spidersand thus, should also reduce prey capture rates.
In this study, we use a British species of the otherwise largely tropical Argiope genus, Argiope bruennichicommonly known as the wasp spider Becker ; Levito test both hypotheses.
We black out the yellow and white bands on some spiders, other spiders are shielded with a leaf fragment and some spiders are left naturally coloured as controls. We predict that if body coloration serves as an attractant, naturally coloured spiders will capture more prey than will either leaf-shielded webs or blacked-out conspecifics.
Alternatively, if bright coloration acts as a disruptive camouflage, leaf-shielded and naturally coloured spiders will have similar insect-capture rates, and both rates will be higher than with blacked-out spiders. A closely related problem in the understanding of spider prey-capture strategies is to explain the function of the silk web decorations historically known as stabilimenta that are typically built by spiders in the genus Argiope.
Therefore, our study also considers the possible effects of silk decoration on prey capture in A. Recording took place between Orb webs are built close to ground level and often contain linear silk decorations, zigzagging vertically from the web hub.
Our study includes only females, as males do not build webs and are dull in colour in contrast to the brightly coloured females. The possibility of prey attraction by silk decoration in A. Treatment 1, leaf-shielded spiders; treatment 2, blacked-out spiders and treatment 3, naturally coloured spiders.
The p values refer to the significance of treatment level in explaining variance in each row value ANOVA, d. We applied two experimental treatments. However, to control for any potential odour effects of the marker pen on treatment 2 spiders, the otherwise naturally coloured spiders treatment 3 were marked on the dark ventral surfaces of the legs, and the leaf shields used in treatment 1 were also marked with the pen on the side facing the spider.
The ventral surface of A. Web decoration is visible in the lower part of b. Treatments were assigned by rotating the treatment as each new individual’s web was located.
A total of spiders were observed, 45 each in treatments 1 leaf shield and 2 blacked out and 70 naturally coloured controls. Orthopteran prey were distinguished as these are the largest prey items. We counted only prey capture by the spiders and not web interceptions that did not result in capture.
As all three treatments contained a spider, we assume that there was no systematic bias in the spider’s ability to capture a prey item that contacted the web. Importantly, the removal of prey by A. Spider body length was recorded to the nearest mm, as was the length in mm of the silk decoration if present.
Hub height from the centre of the web vertically to the ground was recorded to the nearest cm. Owing to the high frequency of zeros in the dataset, indicating that prey capture can be thought of as a Poisson process, we used a generalized linear model Poisson error and log link to identify which of the predictors treatment, spider length, web area, hub height and stabilimentum length significantly explain variance in the total prey and in the Orthoptera captured.
Because all but treatment effects reflect natural variation, we do not test for two-way interactions Crawley We used three response variables: The sum of the latter two categories equals total prey. Finally, any significant or non-significant effect of the variables’ web area, hub height, spider size and silk decoration length must be taken with some caution, as they were not experimentally manipulated and because some exhibit significant correlations, producing multicollinearity data not shown.
Argiope bruennichi – British Arachnological Society
Larger spiders produce webs that are bigger and higher from the ground. Larger webs also have longer stabilimenta, but there is no direct correlation of spider size with stabilimenta length. Analyses were conducted with GLMstat v. Following the field study, the spectral reflectance function of spider body parts was measured with a spectrophotometer AvaSpec, Avantes, The Netherlands relative to a white reflection standard, using a deuterium—halogen light source DH ; Ocean Optics, Dunedin, FL, USA.
Three repeat measurements were taken from an individual recently euthanized by brkennichi from eight different areas outlined in figure 2. Reflectance data were collected from eight points. For colour version see electronic supplementary material. Colour sensitivity was based on the perception of bees, as their visual ecology has been studied most conclusively.
The relative amount of light absorbed by each photoreceptor class is given by P. The sensitivity factor, Rbruennidhi determined by. The nonlinear transfer function relating the receptor excitation, Eto photoreceptor absorption, Pis given as. This three-dimensional space can then be plotted in a colour hexagon allowing us to visualize a bee’s subjective coloured view of the world Chittka Euclidean distances D St between plotted stimuli are calculated as Tso et al.
The distances between colour loci are correlated with a bee’s ability to discriminate between those colours.
The sex pheromone of the wasp spider Argiope bruennichi.
The minimum significant distance used was 0. Mean adult-female body length was Across treatments, there was no significant difference in web area, hub height, spider size or bruennich decoration length table 1.
Spiders in treatment 3 bruenichi coloured captured on average more than twice as many total bruennicih, and approximately three times as many orthopterans, as did spiders in the other two treatments figure 3. Pooling treatments 1 leaf shield and 2 blacked out did not increase residual deviance by a significant amount total prey: Thus, the higher level of prey capture observed in naturally coloured spiders argiole statistically significant, and the blacked-out and leaf-shielded spiders were not significantly different in prey capture success figure 3.
Mean non-orthopteran dark grey bars and orthopteran light grey bars prey per wrgiope caught by spiders in each treatment 1, leaf-shielded individuals; 2, blacked-out individuals; and 3, naturally coloured individuals.
Differences between hexagon coordinates represent a sliding scale of distinction and although no statistical test can be used to test the significance of any observed difference in this case, the current opinion is that values over 0. The majority of colours on a wasp spider immediately obvious to human eyes appear to register as distinct afgiope a bee’s vision as well table 2figure 2 and the electronic supplementary material, appendix A.
Notable exceptions, though close, are the dark and light leg stripes that were not different enough from each other to be classed as distinguishable. Distances between colour coordinates produced from reflectance data of separate areas of A. Colour differences greater than 0. This study has shown that naturally coloured wasp spiders, A. This result supports the hypothesis that bright coloration arggiope wasp spiders attracts insect prey.
These results do not support the disruptive-camouflage hypothesis because leaf-shielded and thus, apparently empty webs should have captured as much prey as did naturally coloured spiders, but did not. By contrast, another investigation concluded that coloration in A. Argiope bruennichi webs bruennnichi more prey bruuennichi did L. However, there were also striking differences in prey composition; Orthoptera were minimally represented in the intercepted species to the extent that they were excluded from the analysis because they were not typical prey species.
Our results also revealed a significant, though weakly negative effect of hub height, as well as a stronger positive effect of spider size on the capture of non-orthopteran prey. Hub height affects web design, and greater web area has previously been shown to increase prey capture in A. However, since hub height and web area are significantly correlated with each other in our study and spider size is correlated with both of those, any or all could be the causal variable making biological interpretation difficult.
The length or occurrence of silk decorations did not explain variance in prey capture in any of the treatments, contrary to the expectations given that silk decorations increase web visibility and represent an energetic investment by the spider Herberstein et al. So why do almost half of webs contain them?
Conflicting results in the literature have so far meant that no clear conclusion has yet been reached.
It seems probable that decoration has evolved to serve many purposes among different lineages srgiope spiders Herberstein et al. Our spectrophotometer results confirm that A. Specifically, the dark and light yellow stripes on the dorsal abdomen were distinct from all other areas, and the thorax was also divergent from most other areas table 2.
However, the leg stripes are duller table argiopf and therefore less perceptible by insects, which could help to disguise the spider’s outline.
Finally, a possibility not directly tested in this study is that the yellow and black patterning of A. However, during fieldwork, not one blacked-out spider disappeared from its web, and although this is far from conclusive evidence that aposematism does not exist in A. In summary, our study showed that diurnal orb-web spiders are not simply sit-and-wait predators passively filtering prey from the air.
Argiope bruennichi appears to have evolved bright coloration to create a sensory bruenichi that improves foraging success.
Lower visibility of the legs might also help to disguise the outline of the spider from its prey and from predators of spiders. The authors thank the National Trust for allowing access and helping to locate suitable study populations on Trust property, the University of East Anglia’s undergraduate ecology programme for its independent projects class and Lars Chittka and Adrian Dyer for their help on the collection, analysis and write-up of the spider reflectance data.
National Center for Biotechnology InformationU. Bruennihi List Proc Biol Sci v. Published online Mar