Sensory exploitation of insect face cues by courting peacock spiders: A test using computer vision

Males use multiple tactics to capture and maintain female attention during courtship. These can include exploiting female sensory biases toward stimuli associated with foraging or shelter, as well as exploiting female anti-predatory responses. In the jumping spider genus Maratus, male courtship involves the display of complex abdominal patterning that for some species appears to mimic facial features of common jumping spider predators (e.g., wasps, mantids), at least to human observers.  We therefore hypothesized that some Maratus species have evolved predator-mimicking courtship displays to influence female behavior early in courtship. To evaluate this, we used computer-vision and machine learning to investigate the likelihood that a simulated female Maratus viewer might misclassify a courting male’s display as a predator face. We find that of 62 species/morphs studied, 13 are consistently misclassified as predator and/or prey insect faces at rates of 20% and greater. Additionally, our results indicate that males may be more likely to be misclassified as insects during the first stage of courtship, when males are furthest from the female and viewed through her lateral eyes. Our in silico test provides initial support for the possibility that males of some Maratus species might use predator and/or prey-mimicry to exploit female sensory biases in courtship.

Methods
Images were collected from public online photography sharing sites, primarily Flickr. All *Maratus *images come from Jurgen Otto. Images were standardized using Adobe Photoshop CS5.1. Analysis in MATLAB uses the Histogram of Oriented Gradients feature extraction method and support vector machine multiclass classification, iteratively running 10 iterations of each of the four sighting distances for each of the four image sets. The Results folders include the results of all simulations for both the genus-wide analysis and the single-species analysis. Supplementary Table 1 shows the combined misclassification of *Maratus *across all simulations, sorted by species.