260 



THE WINGS OF CORRODENTIA 



In the remarkable genus Neurostigma described by Enderlein ('oo) from 

 Peru, the pterostigma of the fore wing is crossed by from eight to ten cross- 

 veins. 



Enderlein ('03) in a paper on the Corrodentia of the I ndo- Australian 

 fauna adopts the uniform terminology of the wing-veins and gives an 

 extended discussion of the venation of the wings of this order; this has been 

 of much aid in the making of the following generalizations: 



The costa. — In Psocus, according to the observations of Comstock and 

 Needham, the margin of the adult wing is tubular throughout, there being 



present an ambient vein 

 R 



^^2 + 3 



Fig. 258.^Vings of Stenopsocus (After Enderlein '03). 



A diagram in which the coalesced veins are 



represented separate. 



The costal and anal 

 portions of this vein 

 doubtless represent the 

 costa and the third anal 

 vein respectively, al- 

 though the con^espond- 

 ing tracheae are appar- 

 ently lost. The distal 

 portion of this ambient 

 vein was preceded by 

 the anastomosing tips of 

 all of the wing tracheae, 

 as is shown in the figures 

 of the wings of nymphs. 

 The subcosta. — The 

 subcosta is not forked. 

 In the fore wings of 



nymphs of Psocus (Fig. 256 and 257), the subcostal trachea extends 

 unbranched to the apex of the wing, where its tip enters the forming ambient 

 vein. In the wings of an adult Psocus (Fig. 255), the subcosta is short, and 

 its tip coalesces with the radius in the fore wing and with the costa in the 

 hind wing. In many genera the subcosta consists of two parts : a basal 

 part which lies in the basal part of the costal cell and a distal part which 

 extends from vein Ri to the costa at the base of the pterostigma, the inter- 

 mediate part of the vein being lost. This condition is well shown in the fore 

 •wrng oi Stenopsocus (Fig. 258). 



The radius. — The first forking of the radius, the separation into veins Ri 

 and the radial sector, is quite typical. In the fore wing vein Ri curves 

 back from the costa, bounding the pterostigma; in the hind wing the 

 pterostigma is wanting. The radial sector is usually reduced to a two- 

 branched condition, as in Psocus (Fig. 255) ; in some fomis it is reduced to 

 an unbranched condition, and in others it is not reduced, the four branches 

 remaining separate. 



