HOST LOCATION CUES IN THE SCOTTISH BITING MIDGE CULICOIDESIMPUNCTATUS

A Jennifer Mordue, Amit Bhasin and William Mordue
Department of Zoology, University of Aberdeen, Aberdeen AB24 2TZ, UK.

C. impunctatus is the major biting midge in Scotland and itsopportunistic feeding habits significantly affect livestock and outdoorindustries such as forestry and tourism. Using field trapping, behaviouraland electrophysiological (EAG) techniques we have studied a range of hostrelated cues both singly and in combination and also skin washes from potentialhosts to elucidate those semiochemicals of significance to C. impunctatus. Behavioural bioassays conducted in a flat bed wind tunnel demonstratedthat female C. impunctatus exhibited upwind anemotactic responsesto CO₂ with flight activity positively correlated with tunnelconcentration. Such effects were observed when CO₂ wasreleased either as a plume or as a cloud. In clouds, concentrationsof CO₂ above 0.1% arrested upwind responses. Tunnel bioassaysconducted with putative olfactory stimulants 1-octen-3-ol and acetone alsodemonstrated that upwind responses to these compounds were dose dependent. Their importance was verified by trapping experiments in the field. Single, dual and muliticomponent baiting experiments (+CO₂)further emphasised the importance of octenol as an olfactory stimulantfor C. impunctatus. Concentrations were shown to be paramountin eliciting either positive or negative responses.