NO. 10 MORPHOLOGY OF GNATHOTRICHUS — SCHEDL I9 



Sculpture. — The front and the elytral declivity are the only bearers 

 of specific modifications. The sculpture of the pronotum and the 

 elytra, which is very useful in distinguishing the species in many other 

 genera of the Scolytidac, does not vary to any extent in this genus. 



Secondary sexual characters. — Secondary sexual characters were 

 found in the development of the hairs on the antennae, the number of 

 fully developed tergites and in .the number of spiracles mainly. 



THE HEAD 



The head capsula or cranium (figs. 4-7) is dorsally divided by the 

 epicranial suture. The sutura fronto verticale Berlese or coronal su- 

 ture (figs. 5, 6, Cos) is distinct in all three species examined. In 

 Gnathotrichus retusus Lee, and less pronounced in Gn. materiarius 

 Fitch, this suture and a short piece of the sutura metopica da Miall 

 and Denny or frontal suture become elevated near the junction, form- 

 ing a Y-like ridge. The slightly raised line (figs. 4, 5, a) which origi- 

 nates at the upper margin of the antennal groove (figs. 4, 6, b, 7, c) 

 and which is directed toward this junction may be considered a rem- 

 nant of the frontal suture. These anterior remnants of the frontal 

 suture are never connected with the posterior portion. 



Front.- — The area between the frontal sutures is largely occupied 

 by the frons (figs. 4, 5, 7, Fr). The shape of the front is plano- 

 convex; the median line is slightly raised, and there is a shallow de- 

 pression on each side of the latter. The front is sculptured by scratches 

 which radiate from the center of the anterior margin, and which ex- 

 tend over the entire sclerite, becoming less distinct and less dense 

 towards the outer margin. These scratches look as though they had 

 been made with a needle point, and therefore have been called accicu- 

 lation by several authors. Scattered over the acciculate area are small 

 but deep, sparse punctures. Bristles varying from short to moderately 

 long occur over the entire front ; most of these originate in punctures. 

 They are more numerous in the antero-lateral corners. 



Specific modifications : — 



A — Acciculation strongly developed, close ; front with punctures near 

 the outer margin and antero-lateral region only, with bristles 

 very sparse in the acciculate, area (fig. 5, Ac). 



Gn. snlcatus Lee. 



AA — Acciculation weakly developed or obsolescent, more or less re- 

 stricted to the median anterior area ; front elsewhere punctu- 

 late, bristles more numerous. 



Gn. retusus Lee. and materiarius Fitch. 



