NO. lO 



MORPHOLOGY OF GNATHOTRICIIUS — SCIIFDl, 



51 



TracJication. — All six primary veins (fig. 27) are present and 

 these run roughly parallel and equidistant from each other the whole 

 length of the wing. The costal vein is fused with the corrugated and 

 thickened anterior margin (b) forming an anterior ligature of the 

 wing. The subcostal (Sc), medial (Me), cubital (Cu) and anal veins 

 (An) are simple ; the radius is split into two branches (Rai, Ra2) . The 

 finer divisions of the tracheae permeate the spaces between the veins 

 producing a fine network. Between the adjacent veins there are situ- 

 ated two fairly well defined rows of punctures. 



Sculpture and vestifure. — The occurring punctures are as previously 

 mentioned arranged in approximate rows, being more confused 



h i 



Fig. 28. — GnatJwtrichus matcriarius Fitch : Mandibles of the larva. 



a, apical tooth; b, subapical tooth; c, median tooth; d, molar tooth; e, lateral bristle, or 

 seta (seta mandibulae lateralis) ; /i_2, dorsal setae, or bristles (seta mandibulae lateralis) ; 

 g, retractor tendon; g\, extensor tendon; h, retractor disk; i, extensor disk. 



laterally and on the declivity. The interspaces are minutely recticu- 

 late and punctulate and in all three species about alike. From the 

 punctures originate minute hairs which are slightly longer on the 

 declivity. There also occur longer bristles but they are scarce and 

 scattered over the entire surface, being more numerous on the declivity. 



Lateral unng lock. — On the inner lateral side of the elytra at the 

 level of the anterior margin of the hypopleura a short transverse ridge 

 (fig. 27, Wl) is situated. That ridge is recurved, fitting into a similar 

 formation which is formed by the anterior margin of the hypopleura 

 (fig. I, f, fig. 17, ii). These two parts interlock and are apparently 

 intended to keep the elytra closed. 



Declivity. — The extreme lateral margin of the elytra is subacute. 

 The declivity itself is sloping with a more or less distinct sulcus on 



