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-iusects. 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. Notwith- 
standing, I hud, to my surprise, scale- insects beginning to appear on a large propor 
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. Iu 
a strikingly large number of instances I find two or more leaves bound together with 
silk and occupied by a spidsr, and the inner surfaces of these leaves completely coated 
with scale-iusects, 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 loug-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 passeu- 
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 bivulnerus, engaged in this work, and also the Coccinellids Hyperaspis sig- 
nata and H. bigeminata. In addition to these Putnam mentions Anatis \b-punctata, 
"the larva of a species of Ch ysopa," and "the larvae of two species of JReduviidce ." 
The interesting lepidopterous insect DaTcruma 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, 
