Culiseta melanura (Diptera: Culicidae): population structure and nectar feeding in a freshwater swamp and surrounding areas in southeastern Massachusetts, USA.

Abstract

The population structure and nectar feeding patterns of the mosquito Culiseta melanura were studied in and around a freshwater swamp in the EEE virus enzootic areas of southeastern Massachusetts, USA. During the summer of 1978, resting boxes were used to collect 12,994 female Cs. melanura, 1747 of which were dissected for parity and tested for the presence of plant nectar by the anthrone test for fructose. Large numbers of parous and nulliparous females were present at the perimeter of the swamp habitats and in the upland areas up to 4.8 km from the swamps. Population density fluctuations and seasonal parity rates suggested 4 generations or emergences over the course of the season. Population age structures varied in the 2 habitat types. Blood-engorged and gravid females were more prevalent at the swamp perimeter and nulliparous females were more prevalent outside the swamp. Parous females were equally prevalent in both habitats. Parity rate averaged 23.7% for the season, peaked in mid-summer at 40–45%, and was used to calculate a daily survival probability ranging from 0.749 to 0.814 during the study. Nectar feeding at the swamp perimeter differed between population components; parous females were positive for nectar more frequently than nulliparous females, and both were positive more frequently than gravid females. Nectar feeding outside the swamp did not vary between population components. Overall, the percentage of mosquitoes positive for nectar was higher at the perimeter than outside the swamp. Gravid females contained nectar throughout the egg maturation process. Results are discussed with reference to population dispersal, behavior of mosquitoes in various physiological states, and the EEE virus cycle.