Signal exploitation and manipulation in the predator-prey system of crab spiders (Thomisidae) and bees (Apidae)

Thomisus spectabilis ambush pollinating insects on flowers. We recently found out that these crab spiders exploit the communication between flower and pollinator by identifying and responding to olfactory signals that also attract honeybees. The proposed project will investigate whether the developmental stage as well as various asymmetry patterns of flowers, that are known to influence preferences of honeybees, also effect the choice of crab spiders. It is traditionally assumed that the colourful body of crab spiders functions to camouflage. We were able to show that the colouration of white crab spiders manipulates floral signals by increasing the intensity of reflected light, thus making flowers more attractive to honeybees. Female T. spectabilis are able to undergo white to yellow colour changes. We showed that white crab spiders occupy both white and yellow flowers, while yellow individuals clearly prefer yellow ones. The proposed project will investigate how colour preferences effect bee choice. Our predictions are that white spiders, that reflect more light in relation to the flowers they are naturally found on, attract honeybees to flowers regardless of the colour of substrate they reside on. In contrast, yellow spiders appear as dark dots on white flowers and might thus be avoided by honeybees, whereas residing on yellow flowers they might appear well camouflaged. We will also test the effect of crab spider presence on Trigona carbonaria, a stingless bee that is native to Australia. In contrast to European honeybees, this potential prey species might have evolved a mechanism to avoid predators. The project will broaden our evolutionary understanding of the signalling system between crab spiders and pollinating insects.