Mosquito bites itch because a small amount of an anticoagulant, to which almost everybody is allergic, is injected by the insect when it strikes.

The anticoagulant keeps blood from clotting so that the mosquito can feed on it.

The intensity of the allergic reaction, which causes swelling and itching, varies among humans--some have it worse than others.

This information comes from entomologist E. Craig Turner, who can tell you everything you ever wanted to know about mosquitoes.

A few more tidbits:

* More than 100 species of mosquito are native to Virginia, and in all cases, only the female draws blood.

* Mosquitoes live only two to four weeks, and they usually don't travel more than three-quarters of a mile from where they hatch--unless there is a strong wind or they are really hungry. A female may breed anywhere from several hundred to several thousand offspring.

* There is no "cure" for a mosquito bite, although an ice pack will relieve the swelling. The only way to avoid getting bitten is to apply commercial repellents and to wear clothing that covers all exposed skin.

* Humans are not the only victims. Mosquitoes also attack animals and are known to cause heartworms in dogs. Some varieties of mosquitoes even prefer such coldblooded creatures as lizards and toads.