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 -i inches. In the spring- cocoons 

 can ])e found onl}^ in the more secure places, those spun in more 

 exposed places having been eaten b}^ their enemies. (See PI. VIII.) 



DESCRIPTION OF THE COCOON. 



The cocoon is composed of silk, which is the product of the pair of 

 silk glands common in many orders of insects. These glands are sit- 

 uated on either side of the alimentary 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 cavity or crack 

 in which it is placed. While spinning the larva is bent upon itself 

 and decreases considerably in size. When the cocoon is completed, 

 which takes usually about one day, the larva straightens out and con- 

 tracts in length. While the exterior of the cocoon maj^ 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, wath an average of about da3^s, 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 immediatelv repaired by the larva. 

 Professor Slingerlaud 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 very earl}^ in the si)ring 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 larvas 

 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 10 bands placed on the trees in the 

 early spring G larva3 which were 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 linds 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. 



