Tiger mosquitos are here!

• Author: Barrett, Wayne M.

Despite a lifespan of only four to six weeks and an inability to fly more than a few hundred yards, the dreaded Asian tiger mosquito (Aedes albopictus) has been reported in 351 counties in 24 states since its August, 1985, discovery in Houston, Tex. Normally, another pesky mosquito messing up summer barbeques would be no big deal. However, the tiger mosquito adds a deadly wrinkle - it can transmit eastern equine encephalitis, a rare, but usually fatal, brain disease. It also is a vector for dengue or breakbone fever, a non-fatal disorder endemic to the tropics and subtropics.

There are 3,600 types of mosquitos throughout the world, indicates Carl J. Mitchell, Chief of Medical Entomology at the National Center for Infectious Diseases, Ft. Collins, Colo. What makes this Asian variety especially dangerous is the insect's habit of living near humans and the fact that it is a very aggressive biter. For instance, Florida's salt marsh mosquito, which carries yellow fever, "tends to hover around your ankles, but the tiger mosquito will come right up in your face. They bite more rapidly, and many people say their bites are more painful," explains Charlie Morris of the University of Florida's Medical Entomology Laboratory.

Mitchell and Morris will be part of a collaborative effort this summer investigating the proliferation of Aedes albopictus in Florida. "Although the tiger mosquito has spread across the country and is found as far north as Minnesota, it is very widespread in Florida; that's where the greatest concentration is found," says Mitchell, pointing out that the potentially deadly insect has invaded 64 of the state's 67 counties.

The tiger mosquito was first introduced in Jacksonville in 1986 and initially moved north, not south, because it thrived in temperate, not hot, climates," Morris reports. "But it is a very adaptable insect. What triggers its hatching is light, not temperature. In the fall, there's less daylight than in summer. This tells the eggs that cold weather is coming and not to hatch. That's why it's proliferating in some of the so-called cold weather states." Eventually, in Florida, the tiger mosquito also moved south, altering its biology so it could breed all year long because there is no real change of seasons.

"This insect requires relatively high humidity in the adult stage," Mitchell points out. "It's no accident that it has not been distributed in arid states or the western half of Texas. It's found in Japan, Korea...