However, Phrynarachne spiders may also aggressively mimic bird droppings in order to deceive potential prey. The crab spider genus Phrynarachne is often cited as a textbook example of masquerading as bird droppings in order to avoid predation. In aggressive mimicry, a predator accesses prey by mimicking the appearance and/or behavior of a harmless or beneficial model in order to avoid being correctly identified by its prey. Taken together, our results suggest that insects lured by spiders may misidentify them as bird droppings, and bird dropping masquerading may serve as aggressive mimicry in addition to predator avoidance in P. Finally, visual modeling suggested that spiders and bird droppings can be detected by dipterans and hymenopterans against background leaves, but they are indistinguishable from each other. As predicted, prey were attracted to experimentally blackened or whitened spiders significantly less frequently than to unmanipulated spiders. Both spiders and bird droppings attracted insects at a significantly higher rate than did control leaves. We found that although all prey combined and agromyzid dipterans in particular were attracted to bird droppings at a higher rate than to spiders, other dipterans and hymenopterans were attracted to bird droppings at a similar rate as spiders. We compared prey-attraction rates among bird droppings, spiders, and control empty leaves in the field. To date, there is no experimental evidence to support aggressive mimicry in masquerading crab spiders, therefore, we performed a field survey, a manipulative field experiment, and visual modeling to test this hypothesis using Phrynarachne ceylonica. This study provides, to the best of our knowledge, empirical evidence for the first time that twig-mimicking species can achieve effective camouflage by contour modification. cylindrogaster relies on the resting posture rather than body size for predator avoidance. The results showed that dummies with clustered legs received significantly less attention from predators, regardless of the body length. To differentiate the most important factors in the concealment effect, we manipulated body size (long or short abdomen) and resting postures (leg clustered or spread) of the dummies and recorded the responses of predators to different dummy types in the field. We used cardboard papers to construct dummies resembling spiders in appearance and colour. Here, we studied this deceptive strategy by revealing a special masquerade tactic, in which the animals protract and cluster their legs linearly in the same axis with their bodies when resting, using the spider Ariamnes cylindrogaster as a model. However, contour modification has received far less attention, especially in twig-mimicking species. The role of background matching in camouflage has been extensively studied.
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