152 



MISC. PUBLICATION 273, U. S. DEPT. OF AGRICULTURE 



SAWYERS 



The larvae of the genus Monocharnus^ known as sawyers, are re- 

 sponsible for extensive damage to dying and recently killed and 

 felled trees throughout the United States. The females ch^w irreg- 

 ular pits in the bark, and in these from one to six eggs are placed. 

 The larvae, which are elongated, footless, whitish grubs, feecl from 

 4 to 8 weeks between the bark and wood, loosening the bark and 

 filling the space between bark and wood with long fibrous borings. 

 Later the larvae enter the Avood, forming small oval holes, that 

 become nearly round as the larvae mature. These tunnels extend 

 through the sapwood, often into the heartw^ood, and then turn out- 

 ward to the bark several inches from the point of entrance, thus 

 making U-shaped burrows in the wood. During the early stages of 



larval development 

 the borings are 

 dropped from the 

 galleries a n d form 

 small piles of saw- 

 dust. As the larva 

 nears maturity t h e 

 borings are no longer 

 ejected, and the gal- 

 leries are packed 

 solid, with the ex- 

 ception of a small 

 cell at the end of the 

 gallery in which pu- 

 pation occurs. The 

 mature adult emerges 

 by gnawing a round 

 hole through the thin 

 laver of wood a n d 



Figure To. — Spotted pine st: 



wyers (MonocJiamus macidosus) . 

 X 1.5. 



bark which separates 

 the pujoal cell from the surface. Though the life cycle of these insects 

 is usually completed in 1 year, in the northern portion of the range 

 two seasons are often required. The adult beetles, during flight and 

 egg laying, feed upon the needles of conifers, and some species gnaw 

 the bark from young twigs, many of which are killed. 



The spotted pine sawyer (Monochamiis maculosus Hald.) (fig. 75) 

 is from one-half to 1 inch in length, drab brown, with grayish, 

 irregular-shaped markings. The prothorax is of the same width as 

 the head and has a prominent toothlike projection on each side. The 

 larvae, which range from 1 to 1% inches in length, are destructive 

 to fire-scorched, clying, or recently felled pines and Douglas fir 

 throughout the Western States. 



The Oregon fir sawyer (Monochamus oregonensis Lee.) is a stout, 

 black beetle, approximately one-half to l^^ inches in length, with 

 gray markings, antennae about twice as long as the body, and a 

 toothlike projection on each side of the prothorax. The larvae range 

 from 1 to 1^4 inches in length and are destructive to fire-scorched, 

 injured, dying, or recently felled Douglas fir, balsam firs, and other 

 coniferous trees of the Western States. This is the western variety 

 of the eastern black pine sawyer {M, scutellatus Say). 



