THE WHITE-MARKED TUSSOCK-MOTH. ol 
“From the character of the injury, together with the abundant 
presence of the caterpillar upon the trees at the time, and of no other 
observed depredator, I believed that it was the work of the Orgyia. If 
so, it was of especial interest, as showing a new habit developed, for 
this form of attack had never been recorded of the insect. To verify 
the belief, after ascending some trees and examining branches within 
reach from windows, I went upon a house-top, where the limbs of a 
large elm projecting over the roof gave an excellent opportunity for 
examination. The larve were abundant upon the tree; the flat roof 
was strewn over and heaped in corners with the broken-off tips; very 
many girdled tips still held their place on the tree, and after careful 
search Orgyia larvee were discovered in the act of eating the bark at 
the girdled points. From later observations it appeared that the gird- 
ling had at this time nearly ceased. 
“The following explanation of the cause of the falling of the girdled 
tips seems a rational one. Upon the eating away of the bark by the 
Orgyia caterpillar, the wood rapidly dried from its exposure to the air 
and a‘rest of circulation, and soon became so brittle that from a mod- 
erate swaying of the branches the weight of a half dozen or more of 
large succulent leaves. would occasion the breaking off of the slender 
twig—oftten not exceeding in its dried state the diameter of an ordinary 
pin. 
«For the occurrence at this time of this novel form of Orgyia attack, 
I can only offer the following as a plausible explanation: The spring 
had been remarkably cold, and as a consequence the development of 
the foliage’ had been delayed to quite beyond the ordinary time. The 
sudden advent of warm weather caused a corresponding sudden start 
in vegetation, followed by a vigorous growth, and the young tips of 
the elim would, as the result, be unusuaily tender. The particular feed. 
ing ground of many of the lepidopterous larve is known to be selected 
ouly after repeated tastings and rejections of such portions of their 
food-plant as they traverse and a final acceptance of that most agree- 
able to them. By a process like this the Orgyia may have made the 
discovery that just at the commencement of the new growth, as the 
result of the seasonal conditions above mentioned, there was concen- 
trated in the tender bark nutriment far more acceptable to it than that” 
offered in the leaves, upon which alone it had hitherto been accustomed 
to feed. As the bark hardened with the advancing season it would 
cease to be desirable for food. * * * 
‘On my return to Albany for a few days, on the 21st of July, most of 
the tips then falling and manv of those upon the ground presented a 
new feature. The breaking, instead of being at the base of the girdling, 
just above the commencement of the new growth, was, in these, at the 
preceding node, vovering the growth of the former year. As a rule, 
the twigs showed a greater diameter at their decorticated portion, com- 
pared with those of the earlier fall, and the leaves attached to them had 
been all more or less eaten by the Orgyia. Their greater strength had 
permitted them to remain longer upon the tree, and until the death of 
the preceding internode, which soon followed the arrest of the circula- 
tion—its starvation ensuing—it being unprovided with leaves througli 
which a circulation could still be maintained. When dead, a slight 
movement of the branch by the wind, or even the weight of the terminal 
leaves, would be sufficient to disconnect it at its lower and weaker node. 
In a few instances, where the girdling had been at a little distance 
above the node marking the commencement of the present year’s growth, 
the separation had been at this point, while others separated in this 
