Emergence characteristics of Aedes sierrensis (Diptera: Culicidae) from California treeholes with particular reference to parasite loads.

ABSTRACT

Wing lengths, emergence times, and parasite loads were determined for 8,444 newly emerged adult Aedes sierrensis (Ludlow) collected from 17 treehole emergence traps during a sampling period of 149 d. Peak adult emergence occurred in late spring and early summer, but a small second cohort developed in treeholes retaining water through the dry season. Mosquito production was significantly and positively correlated with the maximum volumes of treeholes. Male and female wing lengths and eclosion times varied significantly among populations from different treeholes; within a population, these variables were highly correlated, suggesting that larvae of both sexes respond similarly to treehole conditions. Egg number (but not longevity) was correlated with adult size for laboratory-maintained females collected from emergence traps. These results suggest variation in the vector potential of adult populations produced from different treeholes. Newly emerged mosquitoes were infected by five parasite species that depend on adult hosts for their dispersal. The mermithid nematode Octomyomermis troglodytis Poinar and Sanders and the ciliate Tetrahymena sp. were very rare in adult populations. Gamontocysts of the ascogregarine Ascogregarina clarki Sanders and Poinar infected the Malpighian tubules of adults from six treeholes. Ectoparasitic larval water mites (near Euthyas) were found on 12% of all adults eclosing from eight treeholes and selectively parasitized female hosts over males. The ciliate Lambornella clarki Corliss and Coats was the most common parasite; it infected males and females from seven treeholes in equal proportions. L. clarki had a significant negative impact on adult populations in that 13% of all females from L. clarki-positive treeholes were infected with ciliates, and infected females are parasitically castrated.