Sensory aspects of host location in mosquitoes

Visual, thermal and olfactory stimuli all contribute to blood meal host location in mosquitoes but olfaction is probably the dominant sensory modality used for this purpose. Much attention has been devoted to the L-lactic acid receptor because it is well characterized and because its sensitivity is a major determinant of host responsiveness in the anautogenous species Aedes aegypti. Studies employing statistical analysis of close to 500 single unit recordings and the scanning electron microscope have demonstrate that L-lactic acid-excited neurons are associated with the shortest sensilla basiconica (grooved pegs) in Ae. aegypti, Culex pipiens, Aedes atropalpus and Aedes epactius. L-Lactic acid-inhibited neurons are found in either short or long grooved pegs, depending on mosquito species. Video recording analysis, a vertical dual-chamber olfactometer and a horizontal dual-port wind tunnel olfactometer have been used to study host location behaviour and nutritional preferences in the obligately autogenous Ae. atropalpus, the facultatively autogenous Aedes bahamensis and the adult diapausing species Cx. pipiens. These behavioural studies, in conjunction with electrophysiological analysis, illustrate the ways in which the interactions between reproductive condition, developmental stage and L-lactic acid receptor sensitivity determine the nutritional choice made between blood and sugar by mosquitoes and demonstrate the role that olfactory sensitivity plays in this process.