Mosquito :: Mosquito (n.) Any one of various species of gnats of the genus Culex and allied genera. The females have a proboscis containing, within the sheathlike labium, six fine, sharp, needlelike organs with which they puncture the skin of man and animals to suck the blood. These bites, when numerous, cause, in many persons, considerable irritation and swelling, with some pain. The larvae and pupae, called wigglers, are aquatic..