6 
every green thing they find. At this time they become, when very 
abundant, an extremely destructive and annoying pest. 
They are about an inch long when full grown, varying from pale 
yellow or grayish to a dark bluish-black hue. (Fig. 4, a, h.) The 
body is covered with long straight hairs grouped in tufts rising 
from small black or orange-yellow tubercles, of which there are a 
number on each segment. When mature, the caterpillars go to the 
ground, into which they burrow a short distance, or they creep 
under shelter above ground, where they form slight cocoons of 
silken web interwoven with the hairs from their bodies. Within 
these they change to dark brown pupae (Fig. 4, c), and in this con- 
dition they pass the winter. The moths emerge in spring and 
lay their eggs in broad patches of several hundred each, on 
the under side of the leaves near the end of a branch, late in 
May and early in June. The adult insect is usually pure white, 
but is sometimes white spotted with black. There are either one 
or two broods of this species, according to the latitude, two in 
southern and central Illinois and probably but one in the northern 
part of the state. 
The simplest and most effective method of controlling these 
insects is to destroy their webs, and the caterpillars within them, 
either by cutting off the twigs which bear them and crushing or 
burning them immediately, or by burning the webs on the tree. 
A bundle of rags or a few corn-cobs, or even a porous brick, wired 
to the end of a pole long enough to reach the nest and saturated 
with kerosene, makes a good torch for the purpose. Care must 
be taken, however, not to injure the tree, and to destroy the scat- 
tering worms which may drop from the nest without being killed. 
Where the infestation is too general to make this method con- 
venient, or where the webs are so high in the trees that they can 
not be readily reached, a spray of arsenate of lead will eventually 
kill the web-worms as they extend their webs over the poisoned 
foliage. Paris green may be used instead, but the lead arsenate 
is to be preferred because, being much more adhesive, it lasts longer 
on the tree. This method is most effective when the caterpillars 
are young, since they are then extending their webs rapidly and are 
likely to be more promptly poisoned than when they are virtually 
full grown. 
The Yellow Poplar - Caterpillar 
{Apatela populi Riley) 
The prominence of the Carolina poplar as a city tree, especially 
in situations where it is difficult to find any other which can en- 
dure the conditions prevailing, makes it the duty of the Entomolo- 
gist to discuss the insect enemies of even this rath.er inferior va- 
riety. 
