326 The American Naturalist. [April, 
THE WHITE-MARKED TUSSOCK-MOTH (ORGYIA 
LEUCOSTIGMA SMITH AND ABBOTT) IN 
CHICAGO. 
Dr. Josera L. Hancock. 
Throughout the months of June and July 1893, there were 
myriads of caterpillars of the White-Marked Tussock-Moth 
(Orgyia leucostigma) crawling on the sidewalks, in the grass 
and in the streets in the section south of the river in Chicago. 
These caterpillars could be seen constantly changing their 
positions, drifting from place to place. One need not have 
searched far to determine the cause of these shifting move- 
ments—for the White Elm trees ( Ulmus americanus) which are 
set out in some of the resident portions, on the sides of the 
streets, at-that time were almost completely defoliated ; show- 
ing that they were infested by this insect. As soon as one 
tree became despoiled of its leaves the caterpillars centered 
their attacks upon other trees adjacent to them. The beauti- 
ful hairy larva of Orgyia marked with yellow, black, and two 
little bright vermillion red: spots on the ninth and tenth joints 
is a conspicuous object. It seems to have few natural enemies 
and parasites that are menacing its welfare here. 
Notwithstanding the possible existence of a few deadly foes, 
it enjoys immunity from these to a larger extent than many 
other insects, as shown from the fact of the growing prepo™- 
derance of individualsin the last three years. The Wheel-bug 
sometimes attack the caterpillars, but the former does not 
occur in the city, whereas bats, cuckoos and robins | 
insufficient numbers to make any appreciable impression eee 
them. In the middle or latter part of August, the male moths 
are most abundant, flying about at night. Attracted by artifi- 
cial lights, they frequently are seen on the glass of the shop 
windows along the streets. One appeared ọn the inside wa 
of a house (August 28, 1893) and was caught by the writer. 
The position of the hairy forelegs placed in front of the body, 
bins are 12 
