NO. lO 



MORPHOI.OGY OF GNATHOTRICHUS SCIIEDL 



25 



Mandibles.- — The mandibles (fig. 9) are very much aUkc in all 

 three species, so much so that it is not possible to distinguish them 

 by mandibular characters. The shape is stout and triangular as in 

 most Scolytidae. The apical tooth (fig. 9, a) and the subapical tooth 

 (fig. 9, b) are well developed and separated by a deep emargination. 

 In contrast to other genera, two median teeth (fig. 9, c) occur. The 

 latter are rather feebly developed and the separating emargination is 

 shallow. The molar tooth (fig. 9, d) is evenly rounded. There are 

 one lateral and two dorsal setae (fig. 9, f, g). Other details are 

 illustrated in figure 9. No specific differences have been found in 

 these. 



Fig. 9. — Gnathotrichus materiarhis Fitch : Mandible, dorsal aspect. 



a, apical tooth; b, subapical tooth; c, median teeth; d, molar tooth; e, dorsal area; /, lateral 

 bristle; g, dorsal bristles; h, transverse ridge; i, anterior fossa; k, condyle; /, posterior 

 fossa; m, posterior impression; n, condyle of ventral articulation; o, extensor tendon; p, 

 retractor tendon; g, extensor disk; r, retractor disk. 



The Maxilla. — The maxillae (figs. 2, 6) are exposed on each side 

 of the labium. Each is held in such a way that the cardo is parallel 

 with the long axis of the head ; the stipes, lacinia, and galea are at 

 right angles to the cardo; the second and third palpial joints are 

 slightly curved outwards. The galea and lacinia are represented by 

 two lobes which are fused except at the apex where they are sepa- 

 rated by a moderately deep notch. The stipes is separated from these 

 fused lobes by a very fine, feeble suture on the outer side ; on the 

 inner side, no suture is evident. Another paper will deal with the 

 generic differences in the maxilla of Gnathotrichus Eichh. and re- 

 lated genera. Nevertheless, it should be noted that, as far as known 

 at present, the labium and the maxillae in the genus Pityophtorus 

 Eichh. always bear at least a few feathered bristles ; in Gnathotrichus 



