Larval behaviour of the winter tick, Dermacentor albipictus (Acari:Ixodidae): evaluation of CO2 (dry ice), and short- and long-range attractants by bioassay

ABSTRACTWe report that larvae of Dermacentor albipictus can detect CO2 from a dry ice source at distances up to 3.0 m and initiate increased activation, movement and questing behaviour. The maximum distance that larvae spread was ~0.5 m after 24 h, compared to 1.0 m and CO2 was required as a carrier. In Petri dish bioassays, larvae arrested into dense aggregations on eggshells collected after hatching. This arrestment was associated with the eggshell lipids cholesteryl oleate and cholesteryl palmitate, implying that cholesteryl esters act as assembly pheromones for larvae. Faster response was evident at 65% relative humidity (RH) versus 95% RH. Larvae were not arrested by tick excreta, guanine or related purines. Although ...