36 
spin its cocoon. These cavities are often found in the interior of 
rotten trees, stumps, and fence posts, with passages excavated into 
these rotten pieces of wood from 2 to tt inches. In the spring cocoons 
can be found only in the more secure places, those spun in more 
exposed places having- been eaten by their enemies. (See PI. VIII.) 
DESCRIPTION OF THE COCOOM. 
The cocoon is composed of silk, which is the product of the pair of 
silk glands common in man}^ orders of insects. These glands are sit- 
uated on either side of the alimentarv canal, and consist of three parts, 
each of which has a separate function. The cephalic portions unite to 
form a single tube in the head of the insect, which extends to the 
external opening or spinneret. The spinneret is a chitinous projection 
on the under side of the labium or lower lip. Throughout its life the 
larva makes use of this silk in various ways. 
When a suitable place has been selected for the spinning of a cocoon 
the larva begins to weave about itself this single thread of silk. The 
exterior outline of the cocoon conforms to that of the cavit^^ or crack 
in which it is placed. While spinning the larva is bent upon itself 
and decreases considera))ly in size. When the cocoon is completed, 
which takes usually about one day, the larva straightens out and con- 
tracts in length. While tne exterior of the cocoon may be rough, the 
interior is always smooth and oval in shape. At completion of the 
spinning of the cocoon the alimentary canal, silk glands, and other 
organs peculiar to the larva begin to disintegrate. 
In from 1 to 19 days, with an average of about days, the larval 
skin is shed and the insect becomes a pupa. The cast larval skin can 
always be found at the caudal end of the body, shriveled into a rounded 
mass. 
Various authors have noted that when the cocoon of the codling 
moth is torn or cut open, it is immediately repaired by the larva. 
Professor Slingerland states that the damage is repaired in winter. 
He has also had a larva spin two or three complete cocoons after hav- 
ing been removed A^ery earl}^ in the spring from the one in which it 
had hibernated. The writer had one spin two new cocoons during 
the sunmier. Professor Gillette notes that in Colorado the larvae 
leaving the cocoons in the earh' spring leave those in which they have 
hibernated and seek other places in which to spin new ones and 
pupate. He reports that under lU bands placed on the trees in the 
early spring 6 larvae which w^ere spinning new cocoons were taken. 
Various reasons might be assigned for this habit of the insect. It 
might be that the cocoons are too deep in the wood of the trunk of 
the tree for the moth to emerge without materially injuring itself, or 
it may be that the larva on becoming active in the spring finds itself 
in a wet place, and, for either of these or some other reason, migrates 
to a better place and spins itself a new cocoon. 
