The tree-hole developing mosquito Aedes triseriatus (Say) is the major vector of La Crosse encephalitis virus in the upper mid-western United States (Calisher and Thompson 1983). This virus overwinters in the eggs of this mosquito, and in the summer infects chipmunks and squirrels which have been bitten by infected mosquitoes (op. cit). Non-infected mosquitoes may become infected when they blood-feed on viremic sciurid rodents (Pantuwatana et al. 1972).
Walker, Edward D.
"Field Evidence Against Rodent Burrow Entering by Aedes Triseriatus (Diptera: Culicidae),"
The Great Lakes Entomologist: Vol. 17
, Article 12.
Available at: http://scholar.valpo.edu/tgle/vol17/iss3/12