The evolution of many animal colours is thought to be driven by selection from visually guided predators. Yet research has largely focused on large vertebrate predators such as birds while ignoring smaller, terrestrial invertebrate predators. This is despite clear evidence that small invertebrate predators are important regulators of prey densities in a variety of ecosystems. Jumping spiders are small voracious predators that feed on a wide variety of prey in the field. They are capable of colour discrimination, but little is known about whether they attend to the colour of their prey during foraging. We examined colour biases by offering Habronattus pyrrithrix jumping spiders arrays of artificially coloured juvenile crickets. We found that field-collected H. pyrrithrix showed populationwide colour biases; across age and sex categories, attack rates were lowest on red and yellow prey (colours commonly used as warning colours) and highest on blue prey. We retested the same individuals after they were housed for several weeks in the laboratory and found that their colour biases had weakened to statistically undetectable levels. We also found that colour preferences in individual spiders were not consistent over time, suggesting that the populationwide colour biases that we observed were not simply driven by consistent preferences of a subset of individuals. Finally, we tested colour preferences in a separate group of naïve, laboratory-raised spiders and found similar biases favouring blue prey, with low attack rates on red, yellow and green. Our study provides the first evidence that both experienced and naïve jumping spiders show colour biases when foraging and suggests that these biases may result from both innate and learned components. We argue that more attention to such understudied predators may provide a more holistic and accurate understanding of the suite of selective pressures that drive the evolution of prey colour patterns, particularly in small invertebrates.

These data are described in detail in the accompanying publication.