DOUGLAS FIR PITCH MOTH. 8 
f 
the seasonal history and habits of insects affecting the growth and de- 
velopment of trees, though a number of caterpillars, of what later 
proved to be this moth, had been caged during the autumn of 1912 for 
observation. Active cooperation in collecting larvee and field notes 
with Messrs. Edmonston, Miller, Burke, Harvey, and all the entomo- 
logical rangers assigned to the various western field stations from 
April, 1918, until late autumn, 1914, made it possible to determine not 
only the insect’s distribution, but its comparative abundance and de- 
structiveness in widely separated regions of the Douglas-fir range and 
also to make this investigation pretty thorough west from the eastern 
boundary of the State of Montana, toward the coast, and north ct 
latitude 41° 30’ to the boundary of the United States. 
LIFE HISTORY. 
THE ADULT. 
The Douglas-fir pitch moth, like all the members of the Sesiidie, 
much resembles, in general appearance, certain wasps and flies. Tlus 
resemblance is especially strong when the insect is in flight. 
The ground color of the insect is black, with rich orange-red spots 
on the thorax and with all! the segments, except the last, banded’ with 
the same color. Underneath the whole insect is rich orange-red. 
Aberrations in color are not frequent but exist, as the rearing of a 
wholly black female would indicate. 
The forewings are transparent, opalescent, with black borders and 
prominent discal mark; the hind wings transparent, with slight discal 
mark and narrow black margin. The spread of wings is from 30 to 
385 mm., about the size of an ordinary “ yellow jacket.” The male 
is about one-third smaller than the female and more slender. 
THE EGG. 
The eggs are brownish, slightly oblong, and are laid singly. A 
single female appears to produce slightly in excess of 30 eggs, the 
issue from two specimens being 34 and 37, respectively. In the field 
their incubation period is about two weeks. 
THE LARVA. 
With the exception of the head, which is dark brown, the larva (fig. 
1) is white; through the transparent skin the darker intestines and 
their contents are plainly visible, thus making this larva readily dis- 
tinguishable from that of Vespamima sequoia Hy. EKdw., which, to a 
slight extent, also infests Douglas fir, but which is more robust, has a 
denser skin, and is dirty white. Especially is this internal dark spot a 
feature in 1 and 2 year old larvae, although it is retained to a marked 
