Learn about caddies worms in this "worming around" activity. Caddis worms are the larvae of caddisflies. The worms carry around the silken cases the flies live in. The word "caddis" comes from an old European word meaning "cotton wool."
Moth-like caddisflies lay their eggs in ponds, marshes, or streams. The nymphs that hatch are aquatic. To protect themselves, they build cases from the materials around them. The nymphs, camouflaged in their cases, can extend their bodies to feed. One kind of caddisfly builds a case resembling a miniature pine cone, bristling with bits of dead leaves. Another builds a long, narrow, cone-shaped case.
What You'll Need:
Caddisfly nymphs (collect from a pond)
Natural material for case-building, such as sand and bits of dead leaves
Step 1: Watch caddisfly nymphs build their cases from material around them. Find caddisfly nymphs in clear, shallow water at ponds and streams. You may be able to catch them with your hands. You can also catch them with a dip net.
Step 2: When you've collected several nymphs, fill some plastic cups with pond water, one for each nymph. Gently remove a nymph from its case and put it in a plastic cup.
Step 3: In one cup, break apart the nymph's old case and see if the nymph will use it. In another, try broken-up dead leaves. In another, try sand, dry grass, or anything else "natural."
Step 4: Time the nymphs to see how long it takes them to build cases.
Does it take longer to build a case from one material than another?
Before letting the nymphs go, offer them the same material their original cases were built from and let them make new protective cases.
On the next page, learn how to look for insects in leaves.