Vol. LIX. No. 2633. 
NEW YORK, JULY 14, 1900 
*1 PER YEAR. 
THE PALMER WORM IN WESTERN NEW YORK 
RENEWED ACTIVITY OF AN OLD PEST. 
Its Habits and Means of Control. 
AN UNEXPECTED APPEARANCE.—Early in June 
some of the western New York apple orchards sud¬ 
denly became overrun with small, active caterpillars 
that devoured both foliage and fruit. By June 12 nu¬ 
merous inquiries and specimens began arriving at 
the Station. Nearly every correspondent stated that 
the insect was new to his vicinity. At the time of 
writing, June 27, we have the insect in all of its 
stages, with the exception of the egg. It is undoubt¬ 
edly the same species that, more than 100 years 
ago (1791) was christened “Palmer worm” by the 
people of New England when the caterpillars sudden¬ 
ly appeared in great numbers in many parts of New 
England and New York State. There are but few 
references to this species in our literature on economic 
entomology, but from these it appears that the cater¬ 
pillars have only occasionally appeared in sufficient 
numbers to do serious 'injury. One of the earliest 
references is in the Transactions of the New York 
State Agricultural Society for 1853, pages 190-192. 
This is by Dr. Harris, who gives a brief account of its 
life history and a technical description of the adult. 
He suggested the scientific name Rhinosia pometella, 
which was later changed to Ypsolophus pometellus. 
Dr. Harris states that in June of that year (1853) the 
caterpillars were observed in great numbers through¬ 
out the greater part of New England and in the valley 
of the Hudson. They were found not only upon apple 
trees, but upon other varieties of fruit trees, includ¬ 
ing cherries and plums, and also upon forest trees. 
In 1856 Dr. Asa Fitch, then State Entomologist of 
New York, published in his second report a detailed 
description of the insect 'in all of its stages, with 
the exception of the egg, and the most extensive ac¬ 
count of its life, history and habits that we have 
seen. It was again briefly referred to by Mr. T. 
Glover in the report of the United States Commission¬ 
er of Agriculture for 1864-5, and by Dr. Lintner in his 
first report, pages 300 and 329. 
APPEARANCE OF THE INSECT.—Although it is 
not improbable that the caterpillars can be found in 
limited numbers in orchards throughout the State, 
the reports received indicate that the most serious in¬ 
jury has been confined to Cayuga, Wayne, Monroe, 
Orleans and Niagara counties. None of the reports 
have mentioned serious injury except in apple or¬ 
chards, and at the time of our trip to one of the 
worst-infested districts no indications of important 
injury except to apple trees were found. When full 
grown the caterpillars measure about half an inch in 
length. The most prominent markings are the three 
broad lines extending the full length of the back. 
Although the colors vary, the middle line is 
light yellow with a fine brown line extending 
the middle. The lateral lines vary from a light 
deep reddish brown. The sides and under surface 
the body are sulphv yellow often tinged with green. 
On the sides are numerous small black dots, from 
eaoh of which a small hair arises. The head is pol¬ 
ished and light brown in color. There are 16 legs. 
NATURE AND EXTENT OF THE INJURY.—'The 
caterpillars like to hide uuring the day, but 'if the 
limb is suddenly jarred they will drop into the air 
and hang suspended by a silken thread in much the 
same manner as the Canker worms. They are very 
active, and when confined will tumble about in a 
lively fashion whenever touched. Although both 
foliage and fruit are eaten, the latter seems to be 
preferred. When feeding on the leaves the caterpil¬ 
lars often make shelters for themselvs, although 
many will be found feeding openly. The shelters are 
made in a variety of ways. Very often the tip or 
ragged edge of a leaf 'is folded over and held in place 
by a silken thread, as shown in Fig. 155. This pic¬ 
ture, like all the others accompanying this article, is 
from life. Figs. 155, 157, 158 and 160 are enlarged. 
The others are natural size. Often several small 
leaves will be drawn together forming a kind of nest 
quite similar to that made by the Bud-moth cater¬ 
pillar. A very interesting method of forming a shel¬ 
ter is shown in Fig. 157. The caterpillar has eaten 
YOUNG APPLES EATEN. Flo. 156. 
into the leaf near the middle, and as the injured 
tissue began to wither threads of silk were spun 
across from side to side. At this stage the picture was 
taken. Later, as the surrounding tissues withered 
still more, the edges come closer and closer together. 
They were fastened from time to time with silk, and 
when they finally touched were fastened securely, 
thus forming a somewhat cylindrical shelter. The 
nature of the injury to the leaves is shown in Figs. 
158 and 160. At first only the soft parts are eaten, 
but finally portions of the smaller veins are devoured. 
INJURY TO THE FRUIT.—The injury to the fruit 
is quite similar to that made by the Green fruit- 
worm. The principal difference is that the holes made 
by the Palmer worms are usually smaller and more 
irregular. Very often, also, the young apple is eaten 
into for a short distance over nearly all of one side, 
and within this area deeper holes are made, as shown 
in Fig. 156. It is also very common to find a nearby 
leaf fastened to the side of the fruit in such a man¬ 
ner as to hide the entrance of the burrow. The 
leaves thus brought inio use are usually partially 
eaten and withered, and hence indicate wnere the in¬ 
truder may be found. Judging from the reports re¬ 
ceived, and our own observations in some of the in¬ 
fested orchards, the amount of damage done by this 
insect is considerable. But so far as we are able to 
learn, it is the unsprayed orchards that have suffered 
the most. In the vicinity of Albion I could find but 
very little evidence of injury in the orchards that 
THE WORM FORMING ITS HOME. Fig. 157. 
had been thoroughly sprayed the usual number of 
times, while some of the ursprayed orchards, and one 
in particular, were overrun with the caterpillars, and 
very little fruit was left uninjured. 
DURATION OF FEEDING.—The individual cater¬ 
pillars probably do not feed more than two weeks, 
but they may be found upon the trees for a week or 
more longer. This is probably because some of the 
eggs are laid earlier than others. At the time of 
writing a few caterpillars are left on the trees, and 
they vary in size from about one-eighth inch to nearly 
full grown. After the caterpillars have become full 
grown and are through feeding, they change to the 
pupa or chrysalis stage. This may take place openly 
upon the leaf, as shown in Figs. 157 and 160, or in 
the retreats formed by the caterpillars. In either 
case they are fastened co the leaf by silken threads 
attached to the posterior end. This stage probably 
lasts about 10 days. Caterpillars kept by the writer 
in the laboratory pupated June 18, and emerged as 
moths during the night of June 26. 
THE MOTH AND ITS CONTROL.—The adult in¬ 
sects are slate-colored moths measuring about three- 
eighths of an inch in length, and a little over half 
an inch from tip to tip of the expanded Wings. They 
are rather obscurely marked by a few darker spots 
on the wings. The moth rests with the anterior part 
of the body well up, and the wings folded roof-shaped 
over the back. Viewed from above they are wedge- 
shaped, the head being at the narrow end. They are 
very active, especially toward dusk, and probably 
during the early evening. As the caterpillars feed 
upon the leaves, spraying with the arsenicals will un- 
YOUNG WORMS INJURING TREES. Fig. 158. 
HOME AT TIP OF LEAF. Fig. 155. 
