198 BULLETIN NO. 62. 



ihey reach the cavity in ascending- or descending the trunk. 



In the case of fruit that has been harvested the larvae in leaving 

 the fruit in the unnatural surroundings of the fruit cellar or mer- 

 chant's warehouse readily spin their cocoons in the cracks and 

 crevices of the containing boxes or any other similar places which 

 may be found. 



With the mandibles the larva gnaws out a shallow cavity in the 

 surrounding substance to receive the cocoon. The wall of the 

 coccoon is composed of silk which is produced by the glands in the 

 head placed there by nature for the purpose. With this silk are 

 mixed numerous bits of wood, bark or other substances gnawed 

 loose by the caterpiller and in this manner the cocoon is made to 

 closely resemble its surroundings. Having constructed the coccoon 

 about itself the transformations are begun. The body contracts, 

 changes color slightl}-, and is straightened out lengthwise in the 

 cocoon. The larval skin is molted and the pupa with a very deli- 

 cate covering is left. This covering soon hardens and takes on a 

 brownish color. This change occurs in about 3 days after the 

 cocoon is constructed in the case of the first generation, but in the 

 second brood of larvae, which reaches full growth in the fall, the 

 change from a larva to a pupa. does not occur until the following 

 spring, the larva remaining as such though dormant, through the 

 winter months. It has been shown that in some cases the larva 

 may change its cjuarters in the spring of year, though for what pur- 

 pose is not clear. 



MORTALITY AMONG LARVAE DURING HIBERNATION. 



Besides large numbers of larvae that meet death during the 

 winter by being eaten by birds, many die from other causes and 

 may be found during the winter or spring in a blackened condition 

 in cocoons. The cause of the death of these hibernating larvae 

 is unknown. From these causes it is probable that not over one 

 cjuarter of those larvae that form cocoons in the fall successfully 

 pass the winter and reach the moth stage. 



THE MOTH. 



Figure 2, Plate II. shows a cocoon and pupa shell vacated by 

 a moth in emerging, attached to the under side of a piece of bark. 



