INSECT ENEMIES OF WESTERN FORESTS 89 
quently construct for their pupation. These are often formed on the 
debris of the forest floor, but may be attached to the needles or 
branches of the tree. 
Sawflies, for the most part, complete their life cycle with one gen- 
eration a year. With many species the winter is passed in the pre- 
pupal stage within the cocoon. In the spring the transformation to 
adult takes place. The adults emerge, mate, and deposit eggs in the 
new needles, leaves, or shoots. In some species part of the brood 
does not emerge from the cocoons until the second spring. The 
eggs hatch in about a week, and feeding starts on the foliage. Feed- 
ing 1s completed by the middle of summer, and the slugs drop to the 
ground to prepare for transformation, usually spinning the tough 
papery cocoons. Other species pass the winter in the eggs which 
hatch early in the spring, the larvae completing their feeding and 
transformation by fall, at which time flight and egg laying again 
take place. 
The native sawflies are attacked by numerous parasites that play 
an important part in holding them in check, but weather conditions 
seem to be even more important in determining the number of saw- 
flies in different seasons. 
Direct control can be effected where it is practical to apply arsen- 
ical poisons, such as on shade and ornamental trees, or to forest areas 
by means of airplanes. Usually, however, the cost of control is not 
justified, because of expense, the difficulty of application of dusts, 
and the fact that most outbreaks are rather quickly suppressed by 
natural control agencies. 
In the forests of western North America there are numerous native 
species of sawflies, which, although usually inconspicuous in num- 
bers, may periodically become prevalent enough to cause noticeable 
damage. So far, although extensive defoliations have occurred, the 
actual destruction of timber has been small, and the outbreaks have 
quickly subsided. 
SAWFLIES ON CONIFERS 
A number of species of sawflies belonging to several genera attack 
the needles of pines and other conifers. The adults are colored vari- 
ously, often black or brown, and with yellowish appendages. ‘They 
are usually from one-fourth to one-half inch in length. The males 
frequently have large, feathery antennae while those of the females 
are threadlike. Eggs are laid singly, in slits made in the needles. 
The young hairless larvae first feed in clusters on the nearest 
needles, then as they grow they scatter out over the fohage and feed 
singly. Upon reaching full growth, about the first of September, 
they are from one-half to 1 inch in length, usually greenish, with 
black or brown heads, and have eight pairs of prolegs. Upon com- 
pleting their feeding they usually drop to the ground and form 
brown, papery cocoons in the forest debris, but some may form co- 
coons on the needles or in crevices of the bark, while still others do 
not construct cocoons. The winter is usually passed in the prepupal, 
larval, or egg stage, and the new adults emerge the following spring. 
These sawflies are easily controlled where trees can be sprayed with 
lead arsenate or other stomach poisons. 
Se 6 OEE ar O MMi ad, a . - ~~ 
