62 THE SCOLYTID BEETLES. 



of the maxilla and the anterior angles are extended forward to the 

 base of the palpi. The mentum is represented by the median tri- 

 angular chitinous plate, the posterior section ' of which is produced 

 and narrowed, and the anterior median section is produced ante- 

 riorly between the palpi and supports the ligula. The short, conical, 

 2-jointed palpi are situated on the anterior angles of the mentum 

 and are scarcely longer than the simple lobelike ligula which bears a 

 few simple papillae. 



Hypopharynx and epipharynx. — The position and character of these 

 important elements of the oral opening are shown in figures 40, D, 

 and 41, B. 



Mandibles (fig. 42). — The mandibles are stout, with the laterodorsal 

 surface rugose, except toward the apex, which is produced into an 

 apical tooth; the inner edge toward the apex is provided with a sub- 

 apical tooth and two small irregular medial teeth. The condyle of 

 the ventral angle is globular and fits into the concave fossa (fig. 40, g) 

 of the hypostoma, while in the dorsal articulation the fossa is borne 

 by the mandible and the condyle by the epistoma (fig. 40, d). The 

 small extensor muscle is attached to the outer basal margin midway 

 between the condyles, while the large and powerful retractor muscle 

 is attached to the margin of the more produced inner angle, thus 

 giving a direct lateral motion to the mandibles. 



Tergites (fig. 39). — -The dorsal area of the tergum of the prothoracic 

 segment is undivided, but evidently represents the scutum (e) and 

 scutellum (/) . The dorsal area of the mesothoracic and metathoracic 

 segments has two divisions. The anterior division evidently repre- 

 sents the prescutal lobe (g). There is evidence of a scutal lobe (e) on 

 the lateral area of both segments, as indicated in the abdominal ter- 

 gites, where the scutal lobe appears between the anterior and the 

 posterior lobe. Thus the latter evidently represents the scutellar 

 division, or scutellar lobe (/). 



Sternites. — The sternum of each of the segments has three sections, 

 anterior, median, and posterior, or sternal (h), sternellar (i), and post- 

 sternellar (j). In the thoracic segments the sternal is the larger and 

 projects posteriorly over the middle of the sternellar lobe, which is 

 represented by a coxal lobe each side of the sternal section. In 

 some of the species these lobes have a median chitinous spot or foot 

 callus at the point where a foot occurs in the legged larvae of other 

 Coleoptera. The abdominal sternites have the same number of sec- 

 tions, but the sternellar section i's not covered by the sternal. 



Plexites.— The pleurum of each segment is divided longitudinally 

 by an irregular pleural groove or suture (w) . The lobe immediately 

 below the groove at the end of the sternites may be referred to as the 

 hypopleural (k) and that immediately above it as the epipleural (l). 

 The hypopleura of the thoracic segments represent the episternum, 



