Prey Luring Coloration of A Nocturnal Semi‐Aquatic Predator

Abstract

Body coloration serves a variety of purposes in animals. Diurnal and nocturnal predators such as spiders may use their body coloration to lure prey. We predicted here that the white patches on the forelegs on females of the nocturnal semi-aquatic spider Dolomedes raptor lure prey, explaining why they are primarily displayed when the spider forages along the water edge. To test our prediction, we developed a color vision model assessing whether the patches are visible to pygmy grasshoppers, the spider's primary prey. We conducted a field experiment using cardboard dummies that resemble D. raptor in size, shape, and color, but with half of them lacking leg patches, and we staged interactions between pygmy grasshoppers and D. raptor with and without leg patches in a greenhouse. We found the white patches to be visible to grasshoppers. The dummies with white patches attracted more grasshopper prey than the dummies without the patches. Moreover, grasshoppers were more attracted to spiders when their white patches were present. Our results supported the hypothesis that the white patches of D. raptor lure prey. Our findings, nevertheless, could not be explained as the spider's body coloration acting as a sensory trap but it should not be ruled out. More studies on a wider range of predators and prey will give more meaningful insights into the co-evolution of predatory lures and prey sensory modalities.

Multifunctionality of an arthropod predator’s body coloration

“…After this acclimation period, the spiders were assigned to one of two treatments ( n = 25 in each): manipulated or control. To spiders in the manipulated treatment, we painted the orange region of the ventral abdomen black using a non‐toxic acrylic paint that had been previously used to manipulate spider body colours (Tso et al, ). To spiders in the control treatment, we added the same amount of black paint to the black spot on the spider's ventral abdomen.…”

“…The function of different body colours, for example yellow, white, green, silver and so on, within spider species has been examined in detail (Blamires et al, , ; Tso, Liao, Huang, & Yang, ; Tso et al, ), but bright orange is a relatively rare body colour in spiders. This may be because orange body coloration is a product of cuticle β‐carotenoid deposition (Toews, Hofmeister, & Taylor, ), and few spiders produce cuticular carotenoids de novo or are unable to attain them from their diet (Hsuing et al, ).…”

“…Some spiders use their body coloration to attract mates (Lin, Zhang, Liao, Hebets, & Tso, 2015), as prey lures (Blamires et al, , 2012Tso, Zhang, Tan, Peng, & Blamires, 2016;White & Kemp, 2016;Zhang, Chen, et al, 2015a), to avoid (Bonte & Maelfait, 2004;Brechbuhl, Casas, & Bacher, 2010;Bush, Yu, & Herberstein, 2008;Hoese, Law, Rao, & Herberstein, 2006), startle or confuse predators (Liu, Blamires, Liao, & Tso, 2014;Moya-Lorano, Taylor, & Fernandez-Montraveta, 2003;Zhang, Mao, et al, 2015b), for thermoregulation (Robinson & Robinson, 1978), or perhaps a complex interplay of these functions. Most of what is known about the function of spider body colours emanates from studies of single features, for example conspicuous bright stripes or spots (Blamires et al, 2012;Tso et al, 2016). We accordingly know little about how different colours function when spider bodies display a variety of colours.…”