24 



MISCELLANEOUS FOREST INSECTS. 



frontal suture. The anatomical details are very similar to those of 

 Dcndroctonus. The frontal area is trianjjular, with a distinct median 

 line from the apex to or beyond the middle. The sutural margins 

 are irregular or sinuate. The normal arrangement of the hairs is 

 shown in figure 8. The antennx are very small, conical, 1-jointed, 

 and situated at the anterior extremity of the frontal suture. The 

 epistoma is represented by the thickened anterior margin of the front, 

 with which it is fused. It is usually darker in color, with the an- 

 terior margin declivous and nearly straight, and the lateral angles 

 slightly produced and elevated where they support the dorsal articu- 

 lation of the mandibles. The pleurostoma is represented by the 

 thickened declivous area surrounding the mandibular foramen. 



The mandibles are rather stout, 

 triangular, with 3 teeth on the 

 anterior half of the inner edge. 

 The apical tooth is usually 

 acute, the subapical acute and 

 near the apex, and the third or 

 median tooth obtuse, emargin- 

 ate, or triangular; usually the 

 basal or molar tooth is not rep- 

 resented. The articulation is 

 quite similar to that in larvae 

 of Dendroctonus. The dorso- 

 lateral area of the mandible has 

 a small impression and short 

 bristle. The eyes are repre- 

 sented in some species by mi- 

 nute ])lack spots beneath the 

 exoskeleton, but apparently 

 without lenses. The maxillse 

 (fig. 6) are much longer than 

 broad, with a distinct cardo, 

 and the stipes, palpiger, and 

 inner lobe are fused into one piece; the lateral area is elevated toward 

 the base, as seen in balsam and when removed from the head. The 

 palpi are 2-jointed, and the inner face of the lobes is armed with stout 

 lacinial teeth. The lahium (fig. 6), ventral aspect, has a large, mem- 

 branous submental lobe (o) attached to and contiguous with the integ- 

 ument of the prothoracic sterna and laterally to that of the maxilla; it 

 is also attached by ligaments to the intergular plate. The mentum is 

 represented by a median triangular chitinous ])late near the middle of 

 the submentum. The mentum, palpifer, and ligula are fused, and the 

 palpi are short, conical, and 2-jointed; the inner part of the ligula is 

 membranous and contiguous with the pharynx. The arrangement of 



Fig. 6. — Pissodis sit chensis: Head of larva, ventral aspect. 

 /, Apical papilla of labrum; i, labial hooks; /, gular 

 plate; m, gular area; n, location of gular apodenie; 

 o,sulimental lobe. (Original.) 



