Visual signals in the wing display of a tephritid fly deter jumping spider attacks

Glossiness disrupts predator localisation of moving prey

Movement is the "enemy of camouflage", but most animals must move to find resources, such as mates, food and shelter. Therefore, strategies that disrupt predator localization or speed perception of moving prey can play a crucial role in prey survival. Shiny or glossy appearances, which are characterised by having a high degree of specular (mirror-like) reflection of incident light1, can disrupt predator hunting behaviours towards moving prey2. Different mechanisms may explain this effect3,4,5, but no study has attempted to identify the mechanisms that disrupt perception of moving glossy prey by non-human predators. Here, we present moving glossy green or grey targets to jumping spiders (Maratus griseus) and precisely document predator hunting behaviours using high speed videography. Jumping spiders were less precise at tracking glossy targets compared to control targets, suggesting glossiness may disrupt localisation of moving targets. Importantly for prey, jumping spider attack jumps were substantially less accurate towards glossy prey compared to control targets. These results were independent of underlying target colour, suggesting benefits of glossiness may be generalisable to differently coloured glossy animals. Our results indicate that glossiness, when paired with motion, creates an unpredictable target that is difficult for predators to localise, offering insights into the prevalence of dynamically coloured organisms in nature.

The flashy escape: support for dynamic flash coloration as anti-predator defence

Dynamic flash coloration is a type of antipredator coloration where intermittently appearing colour patterns in moving animals misdirect predator attacks by obscuring the precise location and trajectory of the moving prey. Birds and butterflies with differing dorsoventral wing coloration or iridescent surface structures may potentially benefit from such effects. However, we lack an understanding of what makes for an effective dynamic flash colour design and how much it benefits the carrier. Here, we test the effect of colour flashing using small passerine birds preying upon colourful, moving, virtual 'prey' stimuli on a touchscreen. We show that at fast speeds, green-to-blue flashing colour patterns can reduce the likelihood of pecks hitting the target, induce greater error in targeting accuracy and increase the number of pecks at a stimulus relative to similarly coloured non-flashing targets. Our results support the idea that dynamic flash coloration can deflect predatory attacks at fast speeds, but the effect may be the opposite when moving slowly.

When a glimpse is enough: Partial mimicry of jumping spiders by insects

Many flies and moths mimic the frontal appearance of jumping spiders. This type of mimicry, which we term as partial mimicry, can be distinguished from Batesian mimicry since the mimic has spider resembling patterns only in certain parts of the body, and not the entire body. The presence of spider-like patterns is obvious only at certain angles suggesting that the mimic is frequently targeted by its predators from particular angles. We tested this hypothesis using Deep Convolutional Neural Networks (DCNNs). First, we trained the network on images of forward facing jumping spiders, where features such as the large principal eyes, small lateral eyes and outstretched legs were evident. Then we tested the classifier on images of jumping spider mimicking flies and moths. A probability value according to the likelihood of the image being a jumping spider or not was assigned by the classifier. We show that the classifier was more likely to misidentify mimicking flies and moths as jumping spiders, but that this probability varied according to the species tested. We further tested it on images of flies from different angles and by taking into consideration the visual acuity of potential predators. Our results suggest that neural networks can be efficient tools for testing evolutionary hypotheses, and that partial mimicry may be a result of the effect of the signaling angle and orientation of the mimics in combination with the likelihood that predators may depend on cognitive shortcuts to identify insects as prey. Further experiments incorporating the properties of the visual system of predators (such as vision in ultraviolet) would result in a better understanding of the evolution of partial mimicry.