Elizabeth Lamb, age 10, of Allen Town,  Virginia for her question:

Why does a mosquito bite itch?

The mosquito does not mean to give you an itchy sting, All she wants is a little sip of your blood. She zooms in for a landing on your soft skin and gets ready to pierce a hole with her beak. Next she puts the tiniest of hypodermic needles down into the hole and injects a fluid. The itchy sting is caused by this fluid which is saliva flavored with a very strong acid.

The mosquito must have fresh,, liquid blood. If the blood clots, she cannot draw it up with her tiny siphon. The acid saliva thins out the blood and prevents it from clotting. If you let the bloodthirsty little creature finish her meals she will draw most of the acid liquid out of the wound. The sting is worse when you shoo her away before she has finished her dinner.