THE GENUS DENDROCTONUS. 



63 



and the epimerum is obscurely represented by the epipleura, both 

 of which are but httle, if at all, different from those of the abdomen. 

 The epipleural lobe of the prothoracic segment has a spiracle, while 

 those of the mesothoracic and metathoracic segments are without a 

 spiracle, but has lateral lobes or areas for the embryonic wing. 



Spiracles. — It will be noted in figure 39 and Plate VIII that the 

 prothoracic segment has a spiracle situated on the epipleurite near 



Fig . 42.~Dendroctonus valens: Mandibles of larva. A, Latero-dorsal aspect; B, dorsal aspect; C, lateral 

 aspect; D, apical aspect; a, apical tooth; 6, subapical tooth; c, median tooth; i, molar tooth; c, extensor 

 tendon; /, retractor muscle disk; g, retractor muscle; h, extensor muscle; i, dorsal fossa; J, dorsal condyle; 

 1c, ventral condyle; I, basal ridge. (Original.) 



the epipleurite of the mesothoracic segment. The writer is not cer- 

 tain as to whether or not this really belongs to the prothoracic seg- 

 ment or, as in the abdomen, to the anterior or prescutal division of 

 the mesothoracic segment. The metathoracic segment is plainly 

 without spiracles, but the abdominal segments 1 to 8, inclusive, have 

 spiracles which are more or less distinct, being rather obscure in the 

 first division and in section a3 (see PL I) and without lateral tuber- 

 cles, while in section a4 and subdivision D both the spiracles and 



