Colour matching in an orb‐web spider: a twig‐masquerading species as seen by potential predators

Abstract

Distinct predator groups perceive prey colour and brightness differently because they harbour distinct visual systems. Therefore, the evaluation of the presence of visual-based mechanisms of action in defensive strategies must be assessed from the perspective of the visual abilities of potential predators. Wixia abdominalis O.P. Cambridge, 1882 (Araneae, Araneidae) is a masquerader species that imitates its substrate, the twigs of trees. Using reflectance spectrophotometry and colour visual models, we tested and subsequently corroborated the hypothesis that colour matching occurs in this species based on how it is perceived by the primary spider predators, hymenopterans and birds. These results provide a theoretical basis on the role of colour and brightness in this defensive strategy, indicating that susceptibility to the two main groups of spider predators can be influenced by these characteristics. Then, we discussed the causes and implications of this defensive strategy in W. abdominalis and similar spider species.

Masquerading predators deceive prey by aggressively mimicking bird droppings in a crab spider

“…To model the chromatic channel of dipteran and hymenopteran vision, we used the photoreceptor sensitivities of the fruit fly, Drosophila melanogaster ( Schnaitmann et al 2013 ) and the honeybee, Apis mellifera ( Hempel de Ibarra et al 2014 ; Menzel and Backhuas 1991 ), respectively. As fruit flies and honeybees have tetra and trichromatic vision, respectively, we calculated the Euclidean distance (ΔS) between 2 points in color space ( E UV , E BLUE , and E GREEN for honeybees, E UV , E BLUE , E GREEN , and E RED for fruit flies) following the procedures described in previous studies ( Chittka and Kevan 2005 ; Defrize et al 2010 ; White et al 2017 ; Xavier et al 2018 ; Ximenes and Gawryszewski 2019 ). We used one-sample t -tests to evaluate whether the chromatic contrast values (i.e., mean Euclidian distance) for each spider and BD, each spider and leaf, or each BD and leaf were significantly greater than the dipteran or hymenopteran prey detection threshold of 0.11 and 0.045 hexagon units, respectively ( Théry and Casas 2002 ; Dyer and Chittka 2004 ; Dyer and Neumeyer 2005 ).…”

“…Masquerading is practised by many spiders ( Pekár 2014 ), but only the protective hypothesis has been experimentally tested to date ( Liu et al 2014 ; Zhang et al 2015 ; Xavier et al 2018 ). The sit-and-wait crab spider genus Phrynarachne (Araneae, Thomisidae) is an often-cited example of BD masquerade and widely accepted that BD resemblance functions as protective masquerade ( Cott 1940 ; Edmunds 1974 ; Pekár 2014 ).…”

Shaped by the Sun: the effect of exposure to sunlight on the evolution of spider bodies

“…Body elongation in orb-web spiders may have other functions. For instance, alternative body shapes may provide camouflage among twigs, branches and debris [35,57,58]. Moreover, the thermoregulation efficiency of body elongation may interact with other variables such as colour [14][15][16]31,59] and pilosity [60].…”

Specialisation in prey capture drives coexistence among sympatric spider‐hunting wasps

“…Spider‐hunting wasps are usually confronted with cognitive and physical challenges when capturing many prey taxa, because spiders can use several different defensive strategies to avoid predation, such as the use of shelters (Moura et al , ), protective web resources (Gonzaga & Vasconcellos‐Neto, ), camouflage (Xavier et al , ), and mimicry (Pekár, ). In addition, spiders present a wide range of size, habitat choice, foraging strategy (sit‐and‐wait or wandering), web inclination in web‐building species, and sociality level (aggregated or solitary) (Purcell et al , ; Viera & Gonzaga, ).…”