242 OHIO EXPERIMENT STATION: BULLETIN 332 



They vary in number from 100 to 400 in each mass. The ends of 

 the masses are abruptly cut off, thus differing from the apple tent- 

 caterpillar, its nearest relation, the egg mass of which is more oval 

 in outline and with sloping edges. 



Life history and habits. — The winter is passed in the larval 

 stage, but within the shelter of the egg shell. Upon the arrival of 

 spring, the larvae emerge and begin feeding, provided foliage is on 

 hand, but if the buds are still closed, await the appearance of the 

 leaves. 



All the young of the brood do not appear simultaneously, but 

 there may be as much as a month's difference in the arrival of the 

 earliest and latest oncomers. During the earlier stages of growth, 

 the caterpillars are gregarious, feeding mainly at night or during 

 the cooler portions of the day. At other times they remain clus- 

 tered and at rest on the foliage of the host or on its trunk or 

 branches. When nearly full grown the larvae become restless and 

 wander about ; or in any stage, if the food supply is depleted, they 

 migrate to other plants in true army-worm fashion. In some 

 instances the migrating insects have been reported in such abun- 

 dance that when crossing railroad tracks the crushed bodies of the 

 caterpillars made the rails so slippery that trains were stalled. 



They do not spin a web as the name would signify but feed 

 unprotected on the foliage. They make frequent journeys from the 

 feeding ground to the larger limbs or trunk of the tree and as they 

 pass along leave a slight silken trail. This trail after continued 

 usage becomes well-defined. There is also to be found adhering 

 here and there to the bark of the host, the cast skins of the cater- 

 pillars. Usually about 6 weeks are required for larval development, 

 and at the end of this period each insect seeks a shelter to its liking. 

 Some select quarters among the hanging leaves, others in sheltered 

 situations on the trunk and branches, and still others in refuse on 

 the surface of the ground and Mndred places. Here the cocoon is 

 spun and the larva transforms to the pupal stage. 



The pupal period lasts about 2 weeks, whereupon the adults 

 emerge and pair and oviposition ensues. Since there is but one 

 brood per season, these eggs constitute the over-wintering shelter 

 for the insect. 



Nature of work. — The injury caused by the tent-caterpillar is 

 the destruction of the foliage of the host, and in cases of severe 

 outbreaks this may result in not only the defoliation of single trees 

 but the stripping of entire areas. When occuring on street and 



