46 ASSOCIATION OF ECONOMIC ENTOMOLOGISTS. 



As the great majority of the worms traveled eastward to the choke- 

 cherry bushes and westward to the hackberry tree, it seems plausible 

 to assume that the worms have some sense of direction, probably 

 being guided by the proximity of the trees to which they migrated. 

 But I do not think that they have the " keen sense to guide " them 

 which Riley states to have been the case for the worms in Washing- 

 ton. Judging by my observations upon the stragglers, namely, that 

 they wandered very much in all directions from the cherry trees, and 

 would wander 10 and 100 feet when there were plenty of food plants 

 (choke-cherry) within 10 or 15 feet, it appears to me that the cater- 

 pillars wander very much at random, depending upon chance to find 

 some other food plant. In fact, it seems to be very much of a " cut 

 and try " method. In abundance there probably was a straggler for 

 about every 5 feet of ground surface. In the afternoon I found very 

 few of them. 



One may contrast the infestation of a tree by migrants with the 

 normal infestation from eggs by stating that in the former case it is 

 centrifugal and in the latter centripetal. When it is centrifugal the 

 migrants travel from the trunk to the larger limbs and then to the 

 smaller ones, building their webs on the limbs or in the crotches. 

 From these webs they go out to the leaves to feed. When infestation 

 is centripetal eggs are laid upon some of the outermost leaves, from 

 which the larva? then work toward the center of the tree, eventually 

 traveling down its trunk, provided their number is so great that they 

 require more food than the tree furnishes. 



FEEDING HABITS. 



My observations in this direction clearly show that the worms feed 

 but little, if at all. during the day. At night they leave the nests, or 

 thicker parts of the webs, and move about freely upon the leaves in 

 the thinner parts or those bordering the webs. To determine the 

 periods of feeding I made observation at all hours of the day. but 

 rarely found any but young broods, below the second moult, busy 

 feeding. The few exceptions to this rule were several broods lined 

 up to feed at about 11 a. m. on a rainy day and now and then a colony 

 in some shady place. 



At night this is altogether different. With the beginning of dark- 

 ness the worms break camp and move out upon the leaves, even to 

 the extent of 2 feet and farther from the nest, to feed. Then they 

 may leave the web altogether and feed unprotected except by the 

 darkness, without even a thread of silk to cover them. a This observa- 



« There may have been a fiber of silk connecting the worms with their web. 

 although I have no observations on this point. It is generally understood, how- 

 ever, that such is the case. 



