= BULLETIN 205, U. S. DEPARTMENT OF AGRICULTURE. 
degree until pupation, which takes place in the third season after the 
deposition of the egg. 
The head is small and rounded; the body cylindrical, rather slender 
in comparison with that of the larve of other sesiids. When full 
grown it is from 1 to 13 inches long. 
THE PUPA. 
The pupa is shining brown, armed with transverse rows of spines 
on the back of the abdominal segments, by aid of which it moves 
back and forth at will in the tunnel made by the larva before pupa- 
tion in the covering pitch mass. When ready for the final trans- 
formation the pupa uses these spines for working its way through 
the thin layer of pitch at the mouth of the tunnel, by projecting its 
anterior segments to at least one-half of the entire pupal length 
through the opening, and holding itself securely during the escape 
of the moth. 
SEASONAL HISTORY. 
The pupal period as observed in the laboratory is 30 days, but 
under adverse weather conditions it seems to be prolonged a few 
days. Usually moths appear in greatest numbers the first sunny 
day after a rainy spell. | 
The general emergence of the Douglas fir pitch moth occurs dur- 
ing the month of June, although individuals emerge in Montana as 
early as May 15, and farther west adults may be found by the first of 
that month. On May 20 the writer noted the first female (no maie 
was observed at large during two years of observation) flying up 
and down a Douglas fir tree, evidently in the endeavor to locate a 
favorable spot for oviposition. Fresh empty pupal shells were 
observed protruding from pitch tubes on infested trees as early as 
May 15. A living chrysalis was found early in April, which, 
allowing 30 days for pupation, would evidently result in adults 
appearing early in May. It is rather striking that most of the 
early chrysalids were found at the highest altitudes in which the 
moth is active. This makes it probable that the shortened seasons 
at high altitudes are frequently responsible for an extension of the 
larval period into the fourth year, just as, in consequence of late 
August oviposition at lower altitudes, a certain percentage of the 
insects do not attain maturity during the three years that this species 
requires for development from egg to adult. In such instances the 
larva pupates during the first warm days of the fourth season. 
Occasionally adults emerge up to the last of July and the first part 
of August. 
The mature insect lives only about five days after emerging from 
the pupa, which accounts for its scarcity. Even where its work 
