The Asian Tiger Mosquito (Aedes albopictus) is an introduced species of day-biting mosquito which has been making summers unbearable in parts of the Washington area for the last fifteen years or so. The adults die off during the winter in temperate climates; populations survive via eggs.
Much of the country experienced an abnormally cold winter in 2014, which, I thought, might have had an effect on this obnoxious species. A recent study discovered that Aedes albopictus eggs will suffer 100% mortality after being exposed to temperature of 10° F (-12° C) for four hours, or 5° F (-15° C) for one hour. On January 7, the low temperature at Reagan National Airport was 6° F; on this day the temperature may possibly have met the condition of four hours at 10° F or lower. For most of the spring I held out hope that the cold might have locally eliminated the Asian Tiger Mosquito (until it could recolonize from warmer areas, which one hopes would take a few years).
But then on May 21, I received the first Asian Tiger Mosquito bite of the year. Asian Tiger Mosquitoes are still here, bringing another summer of misery. I assume that ultimately it was a problem of microclimate. Members of the species lay their eggs in holes in trees and other cavities where rainwater accumulates. These cavities presumably created sheltered environments in which the temperature was significantly warmer than that of the surrounding air.