The role of olfaction in host-finding by two specialist predators of hemlock woolly adelgid

The hemlock woolly adelgid (HWA), Adelges tsugae Annand (Homoptera: Adelgidae), is forest pest introduced to eastern North America in the early 1950's. Although this pest occurs on both landscape and nursery stock as well as in natural stands of hemlock forest, pesticides are only practical and effective in urban settings. Ecological and economical considerations prevent utilization of chemical treatment in the forest setting, thus biological control is viewed as the most promising option for slowing the spread of HWA. It is essential for researchers to be able to accurately assess the population levels of biocontrol agents after release into the environment. No method currently exists for sampling HWA predators. This project was designed to determine whether two species of predators are able to utilize olfactory cues from eastern hemlock and/or HWA in host-finding. If predators use olfactory cues, we may develop an attractive sythnetic blend of compounds to draw them to a trap, thereby simplifying the sampling and improving its accuracy. To address this question we executed three experiments. The first involved examination of the antennae of the predators for the presence and abundance of olfactory sensilla. The second experiment was designed to detect a behavioral response by the predators following exposure to host volatile compounds. The final experiment involved identifying compounds emitted from eastern hemlock, and the affect of HWA-feeding on volatile emissions. Laricobius nigrinus Fender (Coleoptera: Derodontidae) antennae are densely populated with sensilla, several of which are potentially olfactory in function. In addition, we observed a behavioral response to olfactory cues which included altered flight behavior. However, the behavior was not clearly attraction. Pseudoscymnus tsugae Sasaji and McClure (Coleoptera: Coccinellidae) has few sensilla on a very short antennae and only one type of sensilla possesses wall pores suggestive of an olfactory functi