response to oviposition-aggregation pheromone Gravid females of Culex quinquefasciatus and Cx tarsalis oviposit preferentially on water where already egg rafts have been laid. IDOMAL:0002093 IDOMAL:0002093 Similar apical droplets have been described from a number of species of Culex, Culiseta, Uranotaenia that lay their eggs in rafts. In Culex, apical droplets are known from pipiens, quinquefasciatus, stigmatosoma, tarsalis and erythrothorax of subgenus Culex and from apicalis of subgenus Neoculex. In Culiseta they are known from annulata and incidens of subgenus Culiseta, and longiareolata of subgenus Allotheobaldia. In Uranotaenia they are known from anhydor of subgenus Pseudoficalbia. Chemical analysis revealed the oviposition aggregation pheromone of Culex quinquefasciatus to be the (-)-(5R,6S) stereoisomer of the fatty-acid lactone 6-acetoxy-5-hexadecanolide. idomal_namespace response to chemical cue during pre-oviposition stage and oviposition