The utilization of patchy thermal microhabitats by the ectothermic insect predator, Cicindela sexguttata

1. Tiger beetles (Cicindela) of open habitats have served as model ectother ms in studies of the dependence of activity and habitat utilization on temp erature. Potential departures from the cicindelid model were investigated i n Cicindela sexguttata, a species inhabiting forests where thermal resource s are patchy and ephemeral. 2. Body temperatures (Tb) were determined by inserting thermocouples into b eetles immediately after observing specific behaviours in the field. Cicind ela sexguttata elevated Tb by basking, foraged at a preferred Tb Of 32.8 de grees C, and stilted, sun-faced, or sought shade when Tb exceeded 35 degree s C. Although these behaviours were typical of Cicinclela, their set points were lower than those of species in more open habitats. 3. Illuminated substrates were utilized for basking and foraging. Beetles w ere dispersed throughout the forest floor in early spring, but became aggre gated in light gaps when the canopy leafed out. Operative temperatures of t hermal models indicated that beetles were unable to maintain the preferred Tb in shade and would not be able to maintain a preferred Tb in light gaps during the autumn, when adults are normally in diapause. 4. Beetles were confined to foraging in light gaps once the canopy was clos ed. Foraging rate and searching speed were independent of Tb, in contrast t o other cicindelids. Adults rarely searched for prey, but ambushed small ar thropods that alighted in the light gap. Dependence on patches of illuminat ion as thermal resources may increase prey capture, intraspecific encounter s, and risk of predation, and preclude foraging in the autumn when Cicindel a species of open habitats are also active.