Identification of potent olfactory stimulants for Culex quinquefasciatus Say (Diptera : Culicidae) and their coding

We employed the Solid Phase Micro Extraction (SPME) and other analytical methods to collect the headspace volatiles from human and animal hosts of Culex quinquefasciatus. Analysis of adsorbed headspace volatiles by Gas chromatography linked antennal detection (GC-EAD) revealed at least four compounds that consistently elicited the responses from the antenna. Chemical identity of these compounds was established by GC-MS. We carried out extensive single sensillum recordings (SSR) on the adult Culex antenna in order to find out if these compounds are detected by specific olfactory receptor neurons (ORNs). One of the sensillum types, ABII-2, indeed detected the dominant compound in host odor spectrum with a remarkable sensitivity. Of the two ORNs present in this sensillum, second ORN detects indole, an aromatic compound that has been previously shown to elicit various physiological responses in many mosquito species. We extended the SSR analysis by exposing each type of antennal sensilla to an array of chemostimuli identified from various host and habitat related sources. The insect repellent DEET was also included in the testing and an ORN in the short trichoid type sensilla responds to DEET in a dose-dependent manner. The identified chemostimuli, the response patterns they elicit from ORNs and other sensory physiological aspects of host attraction and avoidance will be discussed.