[Span., from L. musca, a fly.] A species of gnat that abounds in marshes and woods, and whose sting is very painful. They are very widely distributed, being found in the coldest as well as in the hottest countries. A long proboscis or sucker projects from the head, with several little bristles or lancets sharper than the finest needle. These bristles prick the skin, and the insects draw up the blood through the proboscis, and a poisonous juice is squirted into the wound, which causes great itching, and sometimes a bad sore. It is supposed also that the microbe of malaria is thus implanted in the blood of man. Mosquitoes feed chiefly on the juices of plants, rarely on blood.