FAMILY ZYG.ENID.ffl. 17 



row, less triangular than usual, and less angular at its centre 

 and broader end. The fourth median arises much farther out 

 beyond the middle of the wing than usual, and hence much 

 nearer the three first, the three interspaces being of nearly the 

 same size. 



Secondaries nearly twice as long as broad, though more 

 generally one half longer than broad, reaching half way 

 to, or more rarely beyond the tips of the abdomen. Costa 

 straight, but a little convex in the middle. Apex acute and 

 much produced, or obtuse. The outer edge is nearly as long 

 as the costa, the internal angle much rounded, and the internal 

 edge is one half to a third shorter than the outer edge. The 

 neuration differs greatly as in the primaries. In the typical 

 Zygagnidas the subcostal goes straight to the apex, and the sin- 

 gle fifth nervule arises by an angle connecting with the discal 

 nervules, being equal in length to the four median nervules 

 which are remarkably short, arising at the outer third of the 

 wing. In Ctenucha and also in Alypia the subcostal sends off 

 a branch as usual, which is not angulated near its origin, 

 while the median nervure has only three branches, which arise 

 near the middle of the wing. 



The legs are rather stout, but well proportioned, the joints, 

 in the typical species of very uniform size throughout, and 

 thinly scaled, while in the Castniares they are stouter, more 

 sphingiform with long sharp spines, and hairy femora, while 

 the anterior tibia3 are densely pilose. 



Abdomen short, being generally twice the length of the tho- 

 rax, and thick, obtusely pointed at the tip, sometimes partly 

 truncate. The scales in this family are fine, powdery and 

 scattered thinly over the surface, often leaving naked spots on 

 the wings. Upon the thorax and head the squamation is so 

 fine and thin that the different parts beneath can be often 

 easily distinguished. In the Castniares the scales become 

 larger, more hair-like, approaching somewhat the Sphingidse 



Often when in doubt about the position of some genera of this 

 family, the peculiar dark coloration of this group aids to settle 

 the question. The general color of the Sphingidas is cinereous, 

 that of the Bombycidse is brown, the JEgeriadee and Zygaenidse 

 differ wholly in being bluish, with purplish shades of black or 

 entirely black alternating with gay colors, golden, bronzed, 

 or white and red. However the typical genera are ornamented 



ESSEX INSTITUTE PROCEED. VOL. IV. C. 



