414 FIFTH REPORT OF THE ENTOMOLOGICAL COMMISSION. 



with the words : "I do uofc feel fully prepared to agree with Mr. Riley aud Miss 

 Smith iu regarding all the Pulvinariw found on 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 (Ampelopsis veitchii) on our resi- 

 dence 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 difiScult one. When we consider the great activity of the young lice, however,^ 

 and their propensity for fearlessly crawling upon anything which happens to be in 

 their immediate vicinity, the difficulty is lost sight of. We may recognize as aids in 

 transportation (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 undoubtedly 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-shell 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 interlock, is by a few of 

 the very young larvae, when they are first hatched and are scattered over the limbs of 

 a tree iu 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 particu- 

 lar 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. * * » jf q\i the birds in the world were killed ofi", 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 Hyperaspidius coccidivorus, 

 Chilocorus bivubierus, and others, while feeding upon the young larvse of orange scale- 

 insects, carry many of them from one tree to another attached to their backs and 



Mr. Hubbard has more recently come to the conclusion that spiders are very im- 

 portant 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 consid- 

 eration, 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 

 assisting the spread of scale-insects than any other insects. From the beginning of 

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

 together for their nests or lairs almost always proved infested with scale, if infested 

 trees were found in the neighborhood. This I was at first inclined to attribute solely 

 to the protection from enemies and parasites aff'orded by the web and presence of the 

 spider. No doubt, where the source of infection is near at hand, this may give a 

 sufficient explanation of the observed facts. Lately, however, I have been examin- 



