Adaptive change in protective coloration in adult striated shieldbugs Graphosoma lineatum (Heteroptera: Pentatomidae): test of detectability of two colour forms by avian predators
Abstract
Aposematic and cryptic protective coloration occurs in many insects, and some species may change their defensive strategy between or within the same instar. We have studied antipredatory function of colour change in striated shieldbug, Graphosoma lineatum living in Sweden.
The late summer adults of a new generation are pale brown and black and change their coloration to a red and black during hibernation. We tested the effect of coloration in adult G. lineatum on their detectability for avian predators.
Adult, potentially experienced great tits (Parus major) were trained to eat sunflower seeds hidden inside emptied exoskeleton of either pale brown or red G. lineatum. Then the detection time for both colour forms was measured in a dry vegetation environment.
The birds needed more time to find the pale form of G. lineatum than its red form. The pale form of G. lineatum appears more cryptic on withered late summer vegetation than the red form, not only to the human eye but also to avian predators.