No. 384.] THE WINGS OF INSECTS. 905 
principal trachez, and also surrounding the anastomosing 
tracheoles, which tend to group themselves in the positions 
of the cross-veins. 
The most anomalous thing seen here is the position of the 
radial sector, a character which is quite distinctive of this order. 
In the adult wing (Fig. 62) this sector appears to be a branch 
of the media, and it has always been so interpreted. The only 
indication of its connection with the radius is the persistent 
obliquity of an apparent cross-vein between veins M2 and Ry 
just beyond the nodus. 
The crossing of these trachez (Fig. 61) was first figured 
DE 
TOI 
a OO 
LRANS 
: 
Fic. 62. — Adult wings of Cordulegaster sayi, lettered as in Fig. 61. 
(incidentally) by Roster ;1 later it was described and discussed 
by Brauer and Redtenbacher ;? and it was again figured and 
described by Brogniart.? But the effect of this crossing upon 
the homologies of the veins seems to have been overlooked. 
The apparent cross-vein is, in fact, a part of the radial sector; 
the longitudinal trunk connecting the sector with the media is 
not homologous with any of the principal veins, but is a sec- 
ondary structure, developed for mechanical advantage, and the 
radial sector itself should be so termed, notwithstanding it 
appears to be a branch of the media and is far removed from 
1 Roster, D. A. Bull. Soc. Ent. Ital., vol. xvii (1885), Pl. IV. 
2 Brauer u. Redtenbacher. Zool. Anz., Bd. xi (1888), pp. 443-447. 
8 Brogniart. Recherches sur les Insectes Fossiles (1894), pp. 204-208, Pl. VIII. 
