INSECT ENEMIES OF WESTERN FORESTS gQ 



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 is 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 feed.ing 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 w^estern North America there are numerous native 

 species of saw-flies, 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 saw-flies 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 foliage 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, paper^^ 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. 



