We recently received this message (with a little editing on our end) from one of our readers: “I found these larvae inside a big water bin. Are they harmful or helpful/harmless and should be left alone? A few of them swim, but most of them are lurking at the bottom. The body looks like a knot, with a triangle head, and something resembling a scissor at the end of the tail. I have a dog and am curious if they are harmful to him as well?” Here is a photograph he sent us:
We believe that these mysterious larvae are actually mosquito larvae, which are sometimes referred to as “wigglers” or “wrigglers”. While adult mosquitos are not aquatic, the larval stage of mosquitoes are! Adult female mosquitos lay their eggs on or near water, or damp soil. Within a week, the eggs hatch and the larvae, or wigglers, emerge! Mosquito larvae look like small, hairy worms. They are less than 1/4 inch long with a hard round body, a segmented abdomen, and a siphon tube at the end of its abdomen. We believe the “knot” our reader described is the hard round body, and the “scissor at the end of the tail” is the siphon tube, which is a tubular organ that serves as a breathing tube. Mosquito need a lot of energy to grow, and feed constantly on algae, fungi, and other microorganisms in the water. As they eat and continue to grow, the larvae molt (shed their skin to prepare for new growth) 4 times before they pupate and mature into adult mosquitos.