278 



THE WINGS OF MEMBRACIDM 



(Fig. 277), there is a costal trachea; but is is closely oppressed to the sub- 

 costal trachea. 



This redtiction of the costal trachea is evidently correlated with an 

 even greater reduction of the corresponding vein in the adult wing. Funk- 

 houser states that "Costa never appears as a separate vein in the adult 

 wing." "In such genera as Thelia, Acutalis, and Glossonotus in which a 

 slight membrane is found cephalad of subcosta but no thickened ridge is 

 present, the vein is probably atrophied. In Ceresa, Micrutalis, Telamona, 

 etc., in which subcosta forms the cephalic margin, the tracheae for costa and 

 subcosta have coalesced. In Heliria, Vanduzea, and Enchenopa the trachea 

 has had an influence on the costal margin to form a thickening near the 

 base of the wing." 



The subcosta. — "Subcosta is constant in character throughout the 

 family. It is strong, straight, and unbranched, and extends the full length 

 of the wing. It is the anterior vein of the wing, owing to the atrophy of 

 costa, and as such often forms the cephalic margin." 



Fig. 282. — The tracheation of the fore wing of a nymph of Thelia bimacidata 



(After Funkhouser). 



The Radius. — An exceedingly interesting result obtained by Funkhouser 

 was the elucidation of the structure of the radius in this family. Here the 

 radius appears, as a rule, to be reduced to a two-branched condition with 

 what appears to be a cross-vein connecting the cephalic branch with sub- 

 costa. An extended study of this region of the wing revealed the fact that 

 this transverse vein is really vein Ri as indicated in the lettering of Figure 

 279. 



The identity of vein Ri was not apparent at first, as the trachea that 

 precedes it is frequently lacking (Fig. 282), and when present it appears to 

 arise in an abnormal position (Fig. 276). 



"The solution was first found in the wings of Vanduzea arquata and later 

 this, peculiar condition was verified in other genera. The trachea repre- 

 senting Ri, as will be seen from the figure (283), is weak and apparently 

 greatly reduced. It leaves the main stem in the normal position, but runs 

 in close juxtaposition to the radial sector beyond the point at which the 



