Analysis of the Distribution and Abundance of Anopheles quadrimaculatus (Diptera: Culicidae) Larvae in a Marsh

Abstract

Anopheles quadrimaculatus Say larvae were sampled using an area sampling method along point-quadrat transects in a marsh in 1986 and 1987 to estimate absolute population density and describe larval distribution. Larvae were significantly more abundant in 1986 than in 1987, with 152.8 ± 77.1 ($\bar x$ ± 95% CL) larvae/m2 in 1986 and 44.5 ± 21.3 ($\bar x$ ± 95% CL) larvae/m2 in 1987. Nearest neighbor estimates of larval population density (166.5 larvae/m2 for 1986; 37.1 larvae/m2 for 1987) closely approximated the absolute estimates. Taylor's power law and Iwao's density-contagiousness coefficient indicated that larvae were aggregated in distribution. Regression of larval numbers on quantified habitat variables in quadrats of 1986 showed a positive relationship between length of downed, floating plant stems and larval density, where 66% of the variation in larval density was explained by variation in this variable. Direct observations of larvae showed that typical larval posture was with body perpendicular to a downed plant stem-water interface and tail-end to the interface. However, an experiment showed that larvae did not preferentially select interfaces in the laboratory.