52 



SOME INSECTS INJURIOUS TO FORESTS. 



retiring into their holes to rest and for protection from their enemies. 

 The chips cut in excavating the hole in the wood, as well as the excre- 

 ment, are packed between the bark and wood and are not thrown 



a l 



Fig. 19. — The pine sawyer. Gallery: a, Entrance hole in wood; b, emergence hole; c, pupal cell; 

 d, surface scored by larva before entering wood. About natural size. ( Original. ) 



out upon the ground, as appears to be the case with some other species. 

 In moving about from the entrance of the hole in the wood to the 

 place where food is obtained, very distinct channels are made through 

 this mass of refuse (fig. 21). This habit appears to continue until the 



larva is ready to pupate, when, of 

 course, it retires to the pupal cham- 

 ber (fig. 19, c) already constructed, 

 where it remains until the adult 

 stage is reached. Previous to pu- 

 pation the larva extends the gallery 

 in the sap wood until the heartwood 

 is reached. As a general thing the 

 gallery here turns in a longitudinal 

 direction for 2 or 3 inches, then 

 turns again toward the surface, 

 giving the entire gallery a U-shaped 

 appearance (fig. 19). Sometimes 

 the bottom of the "U" extends a 

 short distance into the heartwood, 

 but as a usual thing it merely reaches it. In the bottom of the " U " is 

 to be found the pupal cell. The gallery is here greatly widened and 

 enlarged in order to accommodate the insect while going through its 



Fig. 20.— The pine sawyer: Cross section of pupal 

 cell. About natural size. (Original.) 



