Mosquitoes are known for the irritating bites they cause. These are always the females; the males are innocent. The females need the blood to lay their eggs. When they bite, they release an anti-coagulating substance in the body, so they can suck the blood without it solidifying. This substance causes itching and mosquito lumps. Mosquito larvae are aquatic. They hang just under the water surface in fresh water, where they filter algae and small particles out of the water. The larvae are prey for fish, beetles and other predators.