Handbook of Nature-Study · Lesson LXXXVI · Topic 12: The aquarium and pond insects
86. Caddis-worms and caddis-flies
Goal: Your child can find caddis-worms in their little houses of sticks or stones, describe how they build and move, and recognize the adult caddis-fly.
You'll need
- A clear stream or pond
- A dip-net or kitchen strainer and a white tray or dish of water
- The aquarium from Lesson LXXXIV (optional)
- A hand lens (magnifying glass)
- A nature notebook and a pencil (colored pencils if you have them)
What's in the book
Comstock's story of lying face down by a brook and watching the bottom, where bits of rubbish turn out to be caddis-worms in their cases; the many kinds of cases, how the larva builds and breathes, and the moth-like caddis-fly. Then Lesson LXXXVI's leading thought, method and fourteen questions.
The lesson, step by step
When and where
Spring through summer. In clear streams, pick up stones and look on the bottom side for little tubes of sand grains or tiny pebbles. In ponds, look for moving bundles of bits of stick and leaf. Comstock's method: the caddis-worms "may be captured and then may be placed in the school aquarium."
Safety first
Water safety: an adult stays within arm's reach of young children at the water's edge. Keep back from steep or slippery banks, and wash hands after handling pond water, mud or water creatures.
Put each stone back the way it was. When you have finished looking, put every creature back where you found it.
Keep the big idea in mind
Comstock's "leading thought" is the one idea the lesson is meant to lead to. Read it to yourself now, and save it to share at the end, after your child has looked and answered:
The caddis-worms build around themselves little houses out of bits of sticks, leaves or stones. They crawl about on the bottom of the pond or stream, protected from sight, and able to withdraw into their houses when attacked. The adult of the caddis-worm is a winged moth-like creature which comes in numbers to the light at night.
Find the houses
Where do you find the caddis-worms? Can you see them easily on the bottom of the stream or pond? Why?
Of what are the caddis-worm houses made? How many kinds have you ever found? How many kinds of materials can you find on one case?
Watch one walk
Put a few in the tray of water and wait until they come out.
What does the caddis-worm do when it wishes to walk around?
What are the caddis-worm's enemies? How does it escape them? Touch one when it is walking, what does it do?
Touch it with a grass stem, not a finger.
The builder
If you keep some in the aquarium for a few days:
How does the caddis-worm build its case? Watch one when it makes an addition to its case, and describe all that you can see.
Comstock also asks children to pull a caddis-worm out of its case. We skip that: it can hurt the larva, and an empty case found on the bottom shows the inside just as well.
Put it into words
Ask your child to tell you how a caddis-worm is like a hermit crab or a snail, and how it is different. Then read the leading thought aloud.
Nature notebook
Draw two or three different cases, life size, and label what each is made of. Add a picture of the grown caddis-fly from the book, with its wings folded like a tent.
Afterwards
On a summer night, look at the insects around a porch light near water. Comstock's last question asks: "Can you tell the caddis-flies from other insects?"
Tip
Most caddis-worms need clean water, so people who check the health of streams count them. Finding many kinds is a good sign.