54 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82 



costal hinge (fig. 30, c), is attached by tendons giving the motion of 

 a hinge joint. This attachment enables the subcostal head to move in 

 the pocket. 



Suhcosta. — The subcosta (figs. 3, Sco, 17, Sc, 30, Sco) consists of 

 a chitinous band extending apically as far as the costa and strengthened 

 by two ridges of dense chitin. The basal part, or subcostal head (fig. 

 30, ScoH), as it was called by Hopkins, is anteriorly formed into a 



CqH n SCO Co 



Fig. 30. — Gnaihotrichus rctusus Lee. : Basal area of the wing, wing articulation. 



Co, costal vein; CoH, costal head; Cu, cubital vein; Me, medial vein; Sco, subcostal 

 vein; ScoH, subcostal head; ax, axillary plates; a, costal condyle; b, costal pocket; c, 

 subcostal hintje; d, subcostal labrum; e, condyle of first axillary; /, subcostal fossa; g, 

 membranous fold connecting Me and a.r^; /i, membranous fold connecting Me and Cu; i, 

 membranous fold connecting Cti and a.rs; j, epicondyle of axi; k, scapula arm; I, axillary 

 horn; m, axilla; n. anterior process of axn; o, articulatory margin; p, scapular hook of 

 prescutum; q, apical margin; r. lateral groove; s, axillary tendon; t, u, lateral emarginations; 

 V, posterior part, or handle; zv, anterior part, or blade. 



projection which is composed of a circular band of chitin (fig. 30, c), 

 articulating with the costal pocket. The posterior part forms a fossa, 

 the subcostal fossa (f), which articulates with the condyle (e) of 

 the first axillary. The labrum (d) of the fossa is deeper on the outer 

 side than on the inner. The outer side of the labrum is divided at 

 its free edge by a V shaped groove. 



Radius. — The radius (figs. 3, R, Ri, R2, 17 R) is not directly fu.sed 

 with any of the axillary plates but is basally closely connected with 

 the subcosta. From the point of fusion with the subcosta the radius 



