THE GENUS DENDEOCTONUS. 



53 



In the fourth subdivision the sexes are more difficult to recognize, 

 but the males are distinguished by stouter, more opaque mandibles, 

 broader front, and by a narrower and more elongate antennal club. 

 Whenever there is doubt as to the sex of an individual it can be settled 

 by examining the pygal segments for the characters shown in figures 

 23 and 24. 



Fig. 36. — Dendroctonus valens: Fore intestine, showing details. A, Fore intestine; B, transverse section 

 of proven triculus; C, longitudinal section of same; Z), single plate; ^, teeth; i^, plates; (3, hypopharynx; 

 a, muscles; 6, proventricular teeth; c, posterior condyle of mandibular articulation; d, median fossa 

 of same; «, anterior condyle of same; /, hypopharyngealbracon; .(/, anterior margin; /», hypopharyngeal 

 papilli. (Original.) 



PXJPA. 



The general structure, proportions, and anatomical details of the 

 Dendroctonus pupa are shown in figures 37 and 38. 



Among the distinctive generic characters are the large prominent 

 head and broad pronotum, while among the divisional and specific 

 characters are the sculpture, armatures, etc., of the head, pronotum, 

 elytra, and abdominal segments, as shown in the figures and defined 

 in the synoptic tables and descriptions. 



