432 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 11 
The European Earwig. Mr. Essig’s recent note (p. 338) leads me to record that I 
found a living specimen of Forficula auricularia while unpacking tulip bulbs received 
in Boulder direct from Holland. 
T. D. A. Cockerell. 
Apple Tent Caterpillar. In the Seventeenth Report of the State Entomologist of 
Connecticut (p. 363) reference is made to the practical disappearance of the apple 
tent-caterpillar (Malacosoma americana Fabr.) in many localities of that state in 1917. 
In describing a reason for this marked decrease after several years of great abundance 
the following statement is made:—“The reason for its disappearance cannot be ex¬ 
plained here, but is probably the effect of parasites or other natural enemies. ” The 
writer has also noted a similar phenomenon in several regions of New York but has 
ascribed it to entirely different causes. 
In the vicinity of Syracuse numerous colonies of recently hatched apple tent-cater¬ 
pillars were found during the last week in April following a week of mild spring weather. 
This week of spring weather was followed by five weeks of extraordinarily cool weather. 
Field notes made May 26 record very unexpected observations regarding the brood 
of the tent-caterpillar. Several trees of the wild cherry which for the preceding 
three years had been entirely stripped of their first crop of leaves, were observed 
to show no signs of defoliation. When a more careful examination was made, colony 
after colony of tent-caterpillars were found entirely exterminated, the small tents 
being occupied by the dead bodies of the minute recently hatched larvae. In a few 
of the nests were found from one to five living caterpillars a half inch or more in length, 
the dead larvae which comprised the remainder of the colony being less than a quarter 
of an inch long. According to a rough estimate made at the time, less than one per 
cent of the larvae had survived. It is likely that the ultimate survivers represent a 
much smaller per cent when it is taken into consideration that this species is so de¬ 
pendent upon their tent for protection from inclement weather conditions, and that 
the few survivers of a colony would probably be unable to construct an adequate 
shelter. 
The explanation which at the time we believed accounted for the extraordinary 
mortality among the larvae was the unusual weather conditions of the spring of 1917. 
A recent examination of the temperature records for April and May 1 of that year 
strengthen our belief in the validity of this conclusion. During the five-day period 
from April 18 to April 22 the maximum temperature each day at Syracuse varied 
from 66° to 71° and the minimum daily temperature varied from 42° to 51°. It was 
during this period that the eggs of the tent-caterpillar hatched. During the succeed¬ 
ing period of 26 days (April 23 to May 18) there was only one day (April 29) in which 
the maximum temperature was above 60° and only four on which it was above 55°. 
During the entire month of May the mean temperature for the entire state was 48.2° or 
an average deficiency of 8°. It is likely that the deficiency at Syracuse was even 
greater than 8° for the period from April 23 to May 18. 
During this period the buds of the wild cherry which had begun to open in April ceased 
developing and the prevailing low temperature and frequent rainfall (there being 
only 7 days in the 26-day period when there was no precipitation) prevented the 
caterpillars from feeding so that most of them were killed by starvation before the 
return of normal conditions. That the death of the larvae was not due to parasitic 
or predaceous enemies was evidenced by their size (less than \ of an inch) and by the 
1 Climatological Data, New York Section for April and May, 1917, U. S. Dept. 
Agri., Weather Bureau. 
