Reproductive Caste Beats a Hasty Retreat

Seven species of Australian gall-inducing thrips have a helping caste (soldiers). This caste is morphologically distinct and has been shown to use these physical differences to be a more effective fighting force. Here we investigate behavioral differences between castes of Kladothrips intermedius (Bagnall) when faced with the destruction of the gall; that is, walking behavior rather than fighting. Two parameters, curvilinear velocity (VCL) and linearity (LIN) were used to describe the two dimensional movements of each caste in our experimental setup. In our trials the dispersers moved more directly (LIN) and quickly (VCL) than soldiers. This is consistent with the view that soldiers are behaviorally distinct and committed to life in a gall while, dispersers (second-instars and adults) seem to have somewhere to go.