104 



As the young hatched, they spread in great numbers over the vege- 

 tation in the vicinity of the trees where they had their origin, and 

 attached themselves to a great variety of plants, both shrubby and 

 herbaceous, besides those mentioned above. We found them upon 

 the bass-wood, green ash, American elm, black locust, osage orange, 

 plum, and cherry, and in their second stage upon leaves of clover 

 and smartweed, upon wild cucumber, and upon the gooseberry. 

 In fact, their young occurred, in the middle of July, upon nearly all 

 the herbaceous plants within one or two hundred feet of infected 

 trees ; clover, plantain. Polygonum, mustard, various grasses, and 

 Bidenfi frondosa, being the species apparently preferred. The latter 

 plant seemed to suffer considerably from their attacks, the leaves 

 being paled, spotted with yellow, and slightly curled when worst in- 

 fested. By the latter part of July the larvie in the second stage 

 were common upon the under sides of the leaves of strawberries 

 near infested trees, causing them to contract and curl. 



The ultimate fate of these individuals which fixed themselves upon 

 herbaceous plants and throve there, for a time at least, we neglected 

 to make out, but it is probable that the greater part of them per- 

 ished in autumn, although some may have succeeded in migrating 

 at this period (when the young upon the trees are passing from the 

 leaves to the twigs) to woody plants on which they could maintain 

 themselves until the following season. The fact that in nurseries we 

 sometimes found the young very abundant upon the suckers at the 

 bases of the trunks of trees which were themselves but little infested, 

 tended to confirm this supposition. 



I noticed a marked difference in the stage of advancement of the 

 brood upon different trees, some retaining still a considerable per- 

 centage of the eggs unhatched in the cottony masses attached to the 

 twigs, after others had practically yielded all their young, and the 

 obsolete bodies of the females and the egg masses had fallen to the 

 ground, or were hanging in ragged shreds from the branches of the 

 trees. As late as July 13, on some trees in Bloomington, fully 

 twenty-five per cent, of the eggs were still unhatched. By the 20th 

 of the month the young had nearly all left the nests of the mother 

 bark lice and were established on the leaves, although a few eggs 

 could occasionally be found which were still unhatched. 



By the 16th August the injury effected by this new brood was at 

 its height, and many trees in the vicinity of Bloomington lost a 

 considerable part of their leaves, and the others were blackened and 

 dwarfed, giving the branches a bare and unthrifty look. 



By the 30tli October all the living bark lice had deserted the 

 leaves, except a few found occasionally upon the petioles, but 

 thousands of them occurred upon the under sides of the twigs and 

 branches of nearly every tree of the species worst infested, {Acer 

 dasycarpum) , the twigs bemg often crowded to their very tips. 



The common insect enemies of the species were moderately abun- 

 dant throughout the season, the small black Coccinellid beetle, 

 Hyperaspis signata, whose larva is found embedded within the egg 

 mass devouring the eggs, being the most destructive. 



