NO. lO MORPHOLOGY OF GNATHOTRICHUS — SCIIEDL 55 



extends to the folding hinge on the wing gradnally increasing in 

 width. The anterior horder of the radins becomes the anterior border 

 of the wing just after the reduction of the costa and subcosta. The 

 folding hinge occurs as a V-shaped plate, the point of the V being 

 anterior. From the folding hinge the radius is divided into two 

 branches (Ri and R2). Radius i extends as a broad chitinous band 

 along the anterior border of the wing to its apex gradually diminishing 

 in width. Radius 2 is slightly narrower than Ri, running two-thirds 

 with, and parallel to it. 



Media. — The media (figs. 3, M, 17, M and 30, Me) is connected 

 to axillary four (lig. 30, axi) by a "membranous fold (g) of L shape. 

 Another fold (h) runs posteriorly to the cubitus (Cu). From the 

 base to the level of the folding hinge it is continued as a single vein. 

 At the latter point it is divided into two branches (fig. 3, Mi and M2), 

 both of which extend to the anal margin. The connection between the 

 single basal part of the media and Mi is membranous, while M2 is 

 a direct continuation of the former. 



Cubitus. — The cubitus (figs. 3, Cu, 17, Cu and 30, Cu) is con- 

 nected with axillary three (fig. 30, ax^) by a membranous fold (i) 

 which runs from the base of the cubitus anteriorly. From its base 

 the cubitus proceeds toward the anal margin which it does not reach. 

 No other branches of the cubitus nor an anal vein are present. 



Wing articulation. — The articulation of the wings (figs. 3, 17 and 

 30) is brought about by means of the costal and subcostal heads, the 

 axillaries of the wings, the clavicle and coracoid process of the meta- 

 episternum, the scapular hook of the posterior prealar process of the 

 prescutum and a series of muscles and tendons connecting and moving 

 these parts. The connection of the costa and subcosta to each other 

 and the costa with the metapleuron was discussed before. In the 

 following lines the axillaries and their connection with the meta- 

 tergum and metapleuron will be explained. 



The axillaries are chitinous plates, differing in number in the dif- 

 ferent orders and also it seems in the genera of the Scolytoidea, which 

 function as articulatory accessories. In the genus Gnathotrichus 

 Eichh. four of such plates are distinctly developed. The heads of the 

 costal and subcostal veins are here not counted as axillaries because 

 they are fused with the veins in such a way that separations seem 

 unnecessary. 



First axillary. — The first axillary (fig. 30, axi) or scapular plate, 

 as it was called by Hopkins, is very similar in shape to that of Den- 

 droctonus valens Lee. as it was illustrated by Hopkins. Anteriorly it 

 is produced to a condyle (e) with a distinct epicondyle (j), articulat- 



