Handbook of Nature-Study · Lesson LXXVI · Topic 9: Butterflies and moths
76. The codling moth
Goal: Your child can read the story of a wormy apple: where the caterpillar went in, what it ate, and where it went to spend the winter.
You'll need
- Several apples from an old tree or orchard, some of them wormy (windfalls are fine for looking, not eating)
- A cutting board and knife (for the adult)
- 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 the codling moth: its pinkish caterpillar in the apple, its tunnel to the core, its cocoon under loose bark, the small bronze-marked moth, and the birds that eat it. Then Lesson LXXVI with a long method, fall and spring observations, photographs of young apples at spraying time, and a list of government bulletins.
The lesson, step by step
When and where
Fall, when apples ripen and fall: Comstock's method is to begin "with a study of wormy apples, preferably in the fall when the worms are still within their burrows." In March or early April, look under loose bark on old apple trees for the silk cocoons.
Safety first
An adult does the cutting. Don't eat apples picked up from the ground. Spraying the trees, which Comstock asks about in question 6, is a job for adults with the right gear; the sprays used in her day contained arsenic and are no longer used.
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 codling moth is a tiny brown moth with bronze markings which lays its egg on the apple. The larva hatching from the egg enters the blossom end and feeds upon the pulp of the apple, injuring it greatly.
Outside the apple
Look at a wormy apple. How can you tell it is wormy from the outside? Can you see where the worm entered the apple?
Look at the blossom end (the end opposite the stem) with the hand lens.
Inside the apple
Cut a wormy apple in half from stem to blossom end.
Find an apple with a codling moth larva in it. How large is the worm? How does it act when disturbed?
Make a sketch or describe the evidence of the caterpillar's progress through the apple. Do you find a web of silk in the wormy part? Why is this? Does the worm eat the seeds as well as the pulp of the apple?
Count them
Take a dozen rotting apples, how many of them are wormy? Do the parts of the apple injured by the worm begin to rot first?
Have your child make a tally and say what fraction were wormy.
Bird helpers
How do the nuthatches, downy woodpeckers and chickadees help us in getting rid of the codling moth?
These birds search bark all winter for hidden cocoons. Then ask your child to tell the life story of the moth, and read the leading thought aloud.
Nature notebook
Draw the cut apple, showing the tunnel from the blossom end to the core and out the side. Label where the egg was laid, where the caterpillar ate, and where it left.
Afterwards
In early spring, peel back a little loose bark on an old apple tree (with an adult) and look for small white silk cocoons. Put the bark back.