The mosquito population is starting to pick up, and it's enough to drive people insane, or indoors, or both. Looking for mosquito larvae is one way to make life a little more bearable, if you have any control over your outdoor living space.
Our local mosquitoes rarely travel far from where they hatch. If you can stop them from breeding in your neighborhood, it may be a lot more pleasant to go outside. Even small amounts of water can harbor mosquito larvae -- for tiger mosquitoes, as small as a few teaspoons. And the whole cycle from egg to adult can take as little as six days.
If you've got something that you want to hold water, like a birdbath, either replace the water every few days (we do this with our birdbath) or use dunks that include BT to prevent larvae from maturing (we do this with our pond).
But, when you can't completely beat 'em, just remember: mosquitoes are part of the bottom of the food chain. That blood you donate will be bird food soon.