THE MAPLE SCALE. 415 



ing with great care a lot of one and two year old trees which I set out myself last 

 March. The stock from which these trees were taken was to my certain knowledge 

 almost absolutely free from scale-insects. At the time of setting, the weather was 

 excessively dry and unfavorable; in consequence of which the trees, 600 in number, 

 were badly checked, and to a great extent lost their tops and nearly all their leaves, 

 so that the present growth is all new, produced during the past summer. Notwitli- 

 standing, I find, to my surprise, scale-insects beginning to appear on a large proper 

 tion of the plants. Upon some of them the insects have begun to spread over the 

 branches, and the exact spot where the trouble began is no longer ascertainable. In 

 a strikingly large number of instances I find two or more leaves bound together with 

 silk and occupied by a spitfsr, and the inner surfaces of these leaves completely coated 

 with scale-insects, when not a trace of the insect can be found elsewhere upon the 

 tree. Furthermore, this lot of trees occupies a position west and north of the re- 

 mainder of the grove, in the path of the prevailing [S. E.] winds. The adjoining 

 rows of older trees, on the southeast, are many of them quite badly infested with, 

 for the most part, chaff-scale (Parlatoria pergandii), there being usually a relatively 

 small number of long-scale {Mytilaspis gloverii) mixed with the other species. As is 

 often the case, the proportions of this mixture of species remain quite constant 

 throughout the infested part of the grove. Now, I find in the newly-infested young 

 grove these two scales mixed in about the same proportions, so that no doubt exists 

 in my mind as to the source of their infection. As to the manner in which it has 

 been accomplished, I submit that if, as many persons think, the young lice are trans- 

 ported bodily by the winds, we would have had a very different distribution from that 

 which exists upon the older trees. The larger and heavier young of the chaff-scale 

 would have been carried to a less distance and in smaller numbers than the long 

 scale. (There have been no unusual storms or very high winds during the past sum- 

 mer.) Again, in a chance distribution by the wind I can see no reason for any evi- 

 dent connection with spider-web shelters such as I have mentioned. Individual 

 scale-larvae do not, so far as I have observed, wander far in search of such protec- 

 tion, and do not need it until the colony becomes sufficiently numerous to attract 

 enemies and parasites. The part played by winds is evidently a secondary one, inas- 

 much as nearly all the web-inhabiting spiders make use of the wind to carry them- 

 selves and their bridges of web from tree to tree, and the spiders transport as passen- 

 gers upon their bodies the migrating larvae of the scale insect." 



The agency of winds is, as just stated, a secondary one of great importance in 

 transporting spiders, and is of primary value in the carrying of infested leaves and 

 twigs to greater or less distances. That the young lice are blown bodily from one 

 tree to another by heavy winds, as formerly supposed, has been disproven by the 

 experiments of Mr. Hubbard, who has shown that they will cling tenaciously to a 

 twig or leaf under a heavy blast from a bellows or from the mouth. 



Natural enemies, — The cottony maple scale is subject to the attacks of very much 

 the same natural enemies as other scale-insects. A number of predaceous beetles 

 feed upon the eggs and young larvae. We have observed the common- lady-bird, 

 Chilocorus bivitlnerus, engaged in this work, and also the Coccinellids Hyperaspis sig- 

 nata and H, bigeminata. In addition to these Putnam mentions Anatis Ib-punctata, 

 "the larva of a species of Ch ysopa," and "the larvaj of two species of Reduviidw." 



The interesting lepidopterous insect DaJcruma coccidivora Comstock, was originally 

 bred from this bark-louse. Its larvw construct tubular passages ot silk and wax 

 from one Pulvinaria to another on a thickly infested branch, and eat both the eggs 

 and the waxy filaments which surround them. This insect and its curious habits 

 were described at length by Professor Comstock in the annual report of this Depart- 

 ment for 1879, pp. 241-243. It has been found preying upon Pulvinaria only in the 

 vicinity of Washington, but in Florida destroys both a large Lecanium on magnolia. 



