REPORT OF THE ENTOMOLOGIST. 



353 



these plants as identical, but there is enough evidence to show that 

 this insect is capable of thriving on quite a variety of food plants, and 

 in the cases where it has been directly introduced from the maple there 

 is no question of its identity." We have also found what is evidently 

 the same species doing considerable damage to the Woodbine (Am- 

 pelopsis veitchii)' on our residence at Washington. 



MODE OF SPREADING. 



Owing to the wingless, degraded, and inactive character of the female 

 and the limited capabilities of the young for extended locomotion, the 

 problem as to how the insect spreads from one locality to another seems 

 at first glance rather a difficult one. When we consider the great ac- 

 tivity of the young lice, however, and their propensity for fearlessly 

 crawling upon any tiling which happens to be in their immediate vicinity, 

 the difficulty is lost sight of. W T e may recognize as aids in transporta- 

 tion (1) the transplanting of trees from infested localities to places free 

 from this insect, (2) birds, (3) other insects, (4) winds, and (5) water. 

 The first of these methods needs no comment. The second is undoubt- 

 edly one of considerable importance, though scarcely deserving the 

 prominence given it by some writers. Mr. Walsh, in his first report as 

 State Entomologist of Illinois (p. 41), in speaking of the oyster-sheli 

 bark-louse of the apple (Mytilaspis pomorum), made the following state- 

 ment: 



"In my opinion the only way in which, as a general rule, bark-lice 

 can spread from tree to tree, when the boughs of those trees do not in- 

 terlock, is by a few of the very young larvse, when they are first hatched 

 and are scattered over the limbs of a tree in such prodigious numbers, 

 crawling accidentally onto the legs of some bird that chances to light 

 upon that tree and afterwards flies off to another. I have long observed 

 that when a tree first begins to be attacked by bark-lice, it is only par- 

 ticular limbs and branches that are at first infected, and that these will 

 be swarming while the rest of the tree will be free from lice. And I 

 have further observed that it is the lower horizontal limbs, or branches, 

 or such as birds, with the exception of woodpeckers and nut- hatches, 

 would most naturally perch on, that are first attacked. * * * If all 

 the birds in the world were killed off, I believe that these bark-lice in 

 a very few years would cease to exist." 



This is an extreme view, and we have already shown (First Missouri 

 Ent. Report, p. 15) how little the agency of birds is to be compared 

 with that of insects. In the case of the species under consideration, 

 the copious secretion of honey-dew attracts many honey-loving insects, 

 such as bees, wasps, and flies, and these without doubt carry many of 

 the restless young larvse from tree to tree. Even the natural enemies 

 of the bark-lice assist in this transportation, and Mr. Hubbard states 

 (American Naturalist, May, 1882, Vol. XVI, p. 412) that the Coccinellid 

 beetles Hypcraspidius coccidivorus, Chilocorus bivulnerus, and others, 

 while feeding upon the young larvae of orange scale-insects, carry mauy 

 of them from one tree to another attached to their backs and legs. 



Mr. Hubbard has more recently come to the conclusion that spiders 

 are very important agents in the distribution of scale-insects, in fact, 

 the most important of all agents, and as his remarks apply quite well 

 to the insect and the topic under consideration, we quote from a letter 

 published in Bulletin No. 2 of this Division, pp. 30-31: 



I have reached the conclusion that spiders play a much more important role in as- 

 sisting the spread of scale-insect thau any other insects. From the beginning of my 

 observations I have noticed that leaves which spiders had folded or webbed together 

 23 A — '84: 



