Day-to-day changes in adult mosquito populations are difficult to measure due to the interactions between specific mosquito behavior, environmental influences upon behavior, and the mode of operation of the sampling technique. Mosquito responses to terrain features and various meteorological factors are briefly summarized with the object of improving our understanding of the samples provided by several classes of sampling techniques. The two major environmental influences upon the composition of a sample are the terrain features and several meteorological factors. As each sampling site is unique, a sample provides little direct information of the numbers of mosquitoes within the much broader area it is supposed to represent but it can reflect population changes at the site. However, the population changes usually are masked by meteorological effects upon flight activity. Data from Florida field studies were utilized to adjust trap catches to compensate for meteorological conditions during the catch period to provide more standard samples.