In order to provide better standardized CO2-baited trap samples, the relationship between sample size and evening temperatures was studied. Adult mosquitoes were collected for 3 h centered on sunset by an automatic interval suction trap baited with CO2 in the Upper Rhine Valley, Germany. Aedes vexans females were most abundant, and their blood-seeking activity showed a significant correlation with the evening's average temperature (r = 0.76, P < or = 0.05). A higher degree of correlation was obtained when the number of specimens caught was related to temperature indices (r = 0.93-0.98, P < or = 0.01). A regression equation indicates the lower temperature threshold for Aedes vexans was between 9 and 10 degrees C. For each degree of increase in the average temperature index, it was estimated that a 5.5% greater number of mosquitoes would be trapped. An upper temperature threshold for this species was not observed at average temperatures < or = 23 degrees C. A relationship between catches of Aedes rossicus and Aedes cinereus and temperatures recorded at the site during the study was not found.
