Stabilimenta attract unwelcome predators to orb–webs

Self Cite

SUMMARYUltraviolet (UV) vision plays an important role in interspecific and intraspecific communication in many animals. However, UV vision and its adaptive significance have been investigated in only approximately 1% of more than 5000 species of jumping spiders (Araneae: Salticidae), renowned for their unique, complex eyes that support exceptional spatial acuity and visually based behaviour. To appreciate the adaptive significance of UV vision, it is important to establish whether salticids can perceive UV and whether the perception of UV varies with ecological factors such as light environment. In this study, we measured the UVtransmission properties of the principal-eye corneas of 128 salticid species. We found that the corneas of all measured species were able to transmit UV light, making the perception of UV possible. Three classes of corneal spectral transmission curves were identified; the majority of species had a Class II curve with a less-steep slope and a gradual onset of the transmission cut-off; all the remaining species had a Class I curve with a very steep slope and a sharp cut-off except for one species that had a Class III curve with an intermediate step, which appeared as a shoulder on the descending part of the transmission curve. The T 50 cut-off transmission values (the wavelength at which 50% of the maximum transmission is reached) in salticid corneas vary with species and light habitat. The corneas of species inhabiting open bush had a higher relative transmission at short wavelengths in the UV than forest species. This is the first investigation of corneal transmission in spiders and suggests that UV perception is widespread in salticids.

Section: Discussionsupporting

confidence: 68%

Section: Introductionmentioning

confidence: 99%

Spectral transmission of the principal-eye corneas of jumping spiders: implications for ultraviolet vision

et al. 2012

Self Cite

“…Cheng and Tso provided direct field evidence that A. aemula on webs with cruciate decorations experienced significantly more wasp attacks than those on undecorated webs (Cheng and Tso, 2007). These results (Cheng and Tso, 2007) and those of laboratory studies using Y-mazes (Bruce et al, 2001;Seah and Li, 2001) showed that predators may use cruciate form decorations to locate the spiders. However, responses of wasps to Argiope spiders on webs with linear decorations seem to differ.…”

Section: Discussionsupporting

confidence: 53%

“…Results of this present study showed that compared with linear form decorations, cruciate silk bands can better attract the attention of insects so can serve as a better visual lure. However, results of several recent studies demonstrate that luring prey by decorating webs with cruciate decorations goes with a cost of increased predation risk (Seah and Li, 2001;Bruce et al, 2001;Cheng and Tso, 2007), and there will be a selection pressure to prevent the spiders from consistently decorating their webs (Li and Lee, 2004). Moreover, another pressure in the context of risk learning of prey also selects against consistent building of decorations of a fixed form (Craig, 1994).…”

Section: Discussionmentioning

confidence: 99%

Insect form vision as one potential shaping force of spider web decoration design

Cheng

Yang

Lin

et al. 2010

SUMMARYProperties of prey sensory systems are important factors shaping the design of signals generated by organisms exploiting them. In this study we assessed how prey sensory preference affected the exploiter signal design by investigating the evolutionary relationship and relative attractiveness of linear and cruciate form web decorations built by Argiope spiders. Because insects have an innate preference for bilaterally symmetrical patterns, we hypothesized that cruciate form decorations were evolved from linear form due to their higher visual attractiveness to insects. We first reconstructed a molecular phylogeny of the Asian members of the genus Argiope using mitochondrial markers to infer the evolutionary relationship of two decoration forms. Results of ancestral character state reconstruction showed that the linear form was ancestral and the cruciate form derived. To evaluate the luring effectiveness of two decoration forms, we performed field experiments in which the number and orientation of decoration bands were manipulated. Decoration bands arranged in a cruciate form were significantly more attractive to insects than those arranged in a linear form, no matter whether they were composed of silks or dummies. Moreover, dummy decoration bands arranged in a cruciate form attracted significantly more insects than those arranged in a vertical/horizontal form. Such results suggest that pollinator insects' innate preference for certain bilateral or radial symmetrical patterns might be one of the driving forces shaping the arrangement pattern of spider web decorations.

“…In tungara frogs, for example, male vocal signals lead to a higher risk of predation (Tuttle and Ryan, 1981). Similarly, orb-web spiders might attract both prey and predators by UV-reflecting body markings (Tso et al, 2004) or web decorations (Hauber, 1998;Bruce et al, 2001;Seah and Li, 2001). The signals generated by crab spider colouration may not only be perceived by bees and probably other potential prey, but also by potential predators.…”

Section: Discussionmentioning

confidence: 99%

Colouration in crab spiders: substrate choice and prey attraction

Heiling

Chittka

Chen

et al. 2005

100

SUMMARY Australian crab spiders Thomisus spectabilis ambush pollinating insects, such as honeybees (Apis mellifera) on flowers, and can change their body colour between yellow and white. It is traditionally assumed that the spiders change their colour to match the flower colour, thus rendering them cryptic to insect prey. Here, we test this assumption combining state-of-the-art knowledge of bee vision and behavioural experiments. In the field, yellow spiders are only found on yellow daisies(Chrysanthemum frutescens), whereas white spiders are found on yellow and white daisies. These field patterns were confirmed in the laboratory. When given the choice between white and yellow daisies, yellow spiders preferred yellow daisies, whereas white spiders showed only a slight but non-significant preference for white flowers. Thus, T. spectabilis select background colours according to their own body colour. When viewed from a distance, bees use an achromatic signal produced by their green receptors for target detection. Through this visual channel, white spiders on white flowers, and yellow spiders on yellow flowers are virtually undetectable. From a closer distance of a few centimetres, when bees evaluate colour contrast, the combination of spider colour against different flower backgrounds affected the response of honeybees, but not in ways predicted by a classical crypsis/conspicuousness interpretation. Yellow spiders on yellow flowers are not perfectly matched when interpreted through the colour vision of a honeybee. Nevertheless, honeybees showed indifference to the presence of a spider, equally landing on vacant or spider-occupied flowers. Likewise, white spiders are poorly hidden on white flowers, as white spiders reflect ultraviolet light strongly, while white flowers do not. Surprisingly, bees are attracted to this contrast, and significantly more honeybees preferred white flowers occupied by white spiders. White spiders on yellow flowers produce the highest colour contrast and bees again preferred spider-occupied flowers. Yellow spiders on white flowers were the only pairing where bees rejected spider-occupied flowers, especially in cases where the contrast between the two was relatively strong. Thus, T. spectabilis select flower colours adaptively in a way that deceives honeybees, or at least does not deter them.