34 NEW YORK STATE MUSEUM 
since some of our most destructive introduced species are of relatively 
slight importance in their native countries. The caterpillars feed 
upon the upper surface of the leaves almost entirely and it 1s, 
therefore, relatively easy to apply poison where it will do the most 
good. This considerably simplifies the problem of control and 
renders it fairly easy to keep this pest within bounds until its status 
can be determined or natural enemies have an opportunity to assert 
themselves and prevent widespread and material damage. The 
insect is already sufficiently numerous near the center of the infested 
area to defoliate entire orchards and conditions favor a continuation 
of the spread with its accompanying serious injury unless there is 
early, thorough and general spraying in the infested area next 
summer. 
Recognition characters. This pest skeletonizes apple leaves in 
much the same way as the well-known canker worms, except that 
these latter more usually devour all the vital tissues of nearly every 
leaf, whereas this newly introduced caterpillar generally confines 
its attack to portions of many leaves (frequently practically all the 
leaves on a tree may be eaten in this manner), feeding near the 
center under a slight web and extending upward and outward to 
include most of the tip of the leaf as illustrated in figure 1. Areas 
on each side of the basal part of the leaf are often untouched. 
Frequently the margins to the width of one-half of an inch or so are 
turned over and a badly eaten leaf may present the appearance 
illustrated in figure 2. There is no webbing together and inclosing 
leaves in masses so characteristic of the native fall web worm and 
also seen to a less extent in the nests of the brown tail moth cater- 
pillar. Both of these last-named species produce moderately firm 
to thick webs which inclose the 
leaves, something never done by 
this newly introduced insect. 
Moreover, the caterpillar of the 
apple and thorn skeletonizer is 
active, yellowish, black-spotted, 
practically naked and about half 

Fig. 3 Apple and thorn skeletonizer, : 
Aa eg 5 i an inch long, whereas both of 
an unusually well marked moth. The f 
coloration varies greatly. (X 4) (Au- the above-mentioned tent-mak- 
thor’s illustration) ing caterpillars are distinctly 
hairy, slower in movement and, 
when full grown, an inch or more in length. 
Description. The moth (figure 3) is an obscure grayish brown of 
dark brown, sometimes purplish tinged, insect with a wing spread o 
