OF NORTH AMERICA. 41 



lengths, the thin! not branched and equal in length to the fourth, 

 while the origins of each are opposite the inner third of the fifth, 

 which arises near the middle of the discal space. Two discal nervules 

 of equal length meet to form an angle pointing inwards, from which a 

 fold is thrown inwards along the middle of the discal space. Median 

 nervules much straighter than usual, their interspaces oblong, and of 

 very equal size. Origins of second, third and fourth equidistant. Sub- 

 median nervure long and distinct. 



" Secondaries long and narrow, the apex much produced, the inner 

 angle not reaching to the tip of the abdomen. Costa convex, a little 

 excavated just before the apex. Outer margin two-thirds as long as the 

 costa, angulated slightly on the second median. Inner edge very short, 

 being one-half as long as the costal. First and second subcostal ner- 

 vules nearly equal in length. The upper discal is very long and ob- 

 lique, and with the lower discal is parallel with the outer edge of the 

 wing. But three median nervules present. First, obsolete ; second and 

 third, parallel ; third and fourth shorter than the second and directed 

 downward. Distance between the two first median nervules one-third 

 as great as that between the third and fourth. 



" The slender abdomen is a little more than twice the length of the 

 head and thorax. 



"The coloration is Prussian blue, with saffron bases to the wings, 

 somewhat as in Pyromorpha. 



' ' Compared with other genera of the sub-family, this interesting ge- 

 nus presents some notable differences, all the characters being, as it 

 were, influenced by the close relationship to the Lithosise. This is 

 seen in the dentated antenna, neither simple as in the Lithosi^, nor 

 pectinated as is the rule in its own group. The Lithosian characters 

 also appear in the head, in the form of the clypeus especially ; and in 

 the unusually slender body, with its narrow wings, and elongated scu- 

 tellum of the meso-thorax. Though after all the Zygcenic characters 

 prevail so extensively that it is a little strange that observers after Dr, 

 Harris' time should change his location of the genus to a place among 

 the Lithosiidas. Though the larva is a lichen-feeder and thus in this 

 early stage is like Lithosia and allies, we must consider the insect as 

 simply analogous in its habits as well as structure to that genus, and 

 not be misled by these strong resemblances." 



Packard, Proc. Essex Inst., April, 1864. 



