FAMILY ZYG^BNID^. 41 



in Ctenucha, since it is a little broader than the pro-thorax, 

 while in Ctenucha it is not as broad. The vertex is not so 

 thickly scaled, the front edge of the clypeus is broader and 

 straighter, thus making the whole clypeus square, as long as 

 broad since the sides do ^not narrow so much as usual towards 

 the front edge. Upon removing the scales, the occiput and 

 epicranium are together equal in length to the clypeus. The 

 occiput is transversely oblong, and divided by a mesial impres- 

 sion into two halves, considerably shorter than broad. The 

 epicranium is subtrapezoidal, narrowing rapidly in front, and 

 bilobed anteriorly by a deep mesial impression. The two 

 ocelli are situated, not on either of the pieces, but just below 

 the antennae, and at each side of the suture between the two 

 above mentioned pieces. The clypeus is a little longer than 

 broad. At its base it is obtusely angular between the antennas ; 

 its sides narrowing slightly towards the front edge, which is 

 nearly square. On the basal half of the piece is a narrow 

 ridge. Mandibles very slender, directed outwards, with long 

 fine dense bristles. Labrum small, equilaterally triangular. 

 Maxillas well developed, reaching when unrolled beyond the 

 base of the abdomen. 



Antennae like those of Ctenucha, but with longer and more 

 hairy pectinations. Jn the female the pectinations are stouter, 

 clavate, ending in setae which are more apparant than in Ctenucha. 

 Palpi ascending, acute and slender, reaching beyond the front 

 by a distance equal to that between the bases of the antennae. 

 Thorax rather slender, a little longer than broad. The scutal 

 pieces of the pro- thorax are united closely along the medial suture, 

 each half not being so separate, or so orbicular as in Ctenucha. 

 The patagia are narrow, not reaching to the end of the meso- 

 scutellum. Owing to the thin scanty squamation the form of 

 the tergal pieces of the thorax can be very distinctly seen : the 

 meso-scutellum is hardly as long as broad, and is very obtusely 

 pointed behind. It is much narrower and longer than in Cten- 

 ucha : so also the meta-scutellum, which is rounded behind, and 

 very slightly produced into a slight obtuse angle. 



Primaries thsee times as long as broad, being long and nar- 

 row. Costa straight to the outer third, where it is curved slowly 

 around to the somewhat produced apex. Outer margin one- 

 half as long as the inner, very oblique. 



The costal nervure terminates at the outer third of the wing, 

 and runs very close throughout its length to the edge of the 



ESSEX INSTITUTE PROCEED. VOL. IV. F,. 



