10 A FIELD GUIDE IN NATURE-STUDY 



crawl? How does it eat? Where does it come from? The Cecropia 

 larva, when full grown, spins a silken cocoon in which the chrysalis remains 

 during the winter. Look for such cocoons, not only of the Cecropia but 

 of other moths. Collect several for study (see directions, below). The 

 tomato hawk moth larva burrows into the gound, transforms to its chrysalis, 

 and the chrysalis remains there until the moth comes out of it the following 

 spring. After the larva has disappeared in the soil of the pot leave it a few 

 days before digging up the pupa. 



The leaves of the following plants are the food of many larvae; look 

 over such plants to secure specimens which can be reared. Basswood, 

 butternut, cherry, hickory, pawpaw, poplar, sassafras, walnut, willow, 

 grape, carrot, parsley, everlasting, thistle, and violet. 



The silkworm. -One of the most interesting moths, because of its 

 economic value, is the one that gives us our silk. Send fifty cents to the 

 Kny-Scheerer Co., 410 W. Twenty-seventh Street, New York City, for a 

 batch of silkworm eggs. They will come on a small piece of card which 

 may be put in a covered tumbler with a few fresh mulberry leaves. The 

 eggs will hatch in a few days and the tiny larvae will crawl onto the leaves 

 to feed. Add fresh leaves as necessary and as the larvae grow transfer them 

 to an insect cage where more sprays of leaves may be kept. Keep record 

 of the length of a newly hatched larva and of its length on successive days 

 as it feeds. The full-grown larvae will spin their cocoons. How do they 

 do it? Is the silk thread continuous? How long is it before the moth 

 hatches after the cocoon is complete ? Mating and egg-laying follow, and 

 the eggs will start the cycle again. 



Study of the Cecropia cocoon. -The Cecropia is known as the American 

 silkworm. Note and draw shape of cocoon. Cut it open carefully so as 

 not to injure the contained pupa. Is the silken covering tough ? Is there 

 variation in the thickness of the silken covering? (Compare yours with 

 your neighbors'.) Can you see in the pupa the eyes, legs, antennae, abdom- 

 inal segments ? What advantage is the cocoon to the animal ? Draw the 

 pupa. In the spring the pupa transforms to the moth and comes out of 

 the cocoon. Watch the process either in this or some other moth. Let 

 the moth, limp and bedraggled as it comes out, crawl up on some support 

 like the wire sides of the large insect cage and expand its wings. Watch 

 it to see how this is accomplished. 



Parasitism. -You will be quite sure to find that some of the Cecropia 

 cocoons are full of small silken cocoons instead of the usual pupa. These 

 cocoons will develop into ichneumon flies that lay their eggs in the larvae 

 of Cecropia. The young feed on the blood and later on the internal organs, 

 killing the animal but often not until it has spun its cocoon. If opportunity 



