Wet tree holes can persist even in Florida’s dry winter season, and they serve as an enticing habitat for mosquitoes that harbor the eastern equine encephalitis virus. “Those tree holes are apparently the key that allows Culiseta melanura to really get going and why there are much more of them at high-risk sites than low-risk sites,” says Thomas Unnasch, Ph.D., of the University of South Florida. Shown here is a larval sampling tool being used to collect Cs. melanura mosquito larvae living in standing water near tree roots in Connecticut. (Photo by U.S. Centers for Disease Control and the Connecticut Agricultural Experiment Station, via CDC Public Health Image Library)