AT THE bottom of lakes or ponds you will find soft tubes of mud which curve in every direction. Inside each tube is a small, red, worm-like animal, which is really an insect larva. This larva is commonly called a "blood-worm," because the red color of its blood shows through the clear, thin covering of its body segments. Its mud case is lined with "silk," much like the lining of a caddis worm's case, but it cannot carry its case around while it looks for food. It may leave its house and return to it later, or, if the case is broken or damaged, may simply build another one, since there is never any lack of building material.

This larva does not have jointed legs as a caddis fly larva does, and may at first be mistaken for a worm. However, you will know that it is not one of the true worms, some of which build mud cases and some of which are red, because of its distinct head, and its two pairs of prolegs near the ends of the body. Also, you will usually see two pairs of "blood gills" near the last segment of this larva's body, if you examine it through a hand lens.

A blood-worm eats algae and bits of dead plants. Many fish eat blood-worms. Sometimes a carnivorous nymph or larva eats the blood-worm, and then a fish eats the nymph.

A larva which escapes its enemies will one day become a pupa which breathes through a pair of air-tubes attached to its thorax. The insect which finally emerges from the pupal case is a small fly, called a midge, which looks much like a mosquito. You will often see midges flying in swarms near the shore or over the water.

Each midge has one pair of wings. Mosquitoes also have one pair. One way to tell whether you have captured a midge or a mosquito is to look at the wings through a magnifying glass. The wingveins of mosquitoes are covered with scale-like formations; those of the adult insect which develops from a blood-worm are not.