135 



Palpi short, not extending far beyond the head; the second joint wide; third 

 short, conical, and usually merged in with the second joint, not free as in 

 Petrophora. Fore wings slightly subfalcate, with the costa regularly arched, 

 the apex acute, and the outer edge very oblique; or the wing is shorter, 

 scarcely subfalcate, and the apex obtuse. The hind wings are short, full, and 

 either shaped as in Petrophora or slightly angled ; on the outer edge, some- 

 times the angle is well marked. The wings project well beyond the end of 

 •the abdomen, which is short and thick ; much shorter than in Petrophora, 

 with similar, but less marked, dorsal and lateral tufts, and with an obtuse 

 anal tuft. The venation differs from that of Petrophora in the first subcostal 

 venule being longer, while the second and third are shorter. The discal 

 venules are always perfect; the anterior one being straight or oblique, and the 

 posterior one oblique and usually much bent. There are usually two sub- 

 costal cells, either very unequal (O. ferrugata, pi. 1, fig. 8), or large and sub- 

 equal, as in the closely-related species O. designata (fig. 8a) ; or, as in O. lignl- 

 colorata (fig. 8b), there is but one small cell, and the first costal arises some 

 distance from it. Hind tarsi a little shorter than the tibiae. Coloration: 

 usually with many zigzag lines on the fore wings, arranged sometimes in a 

 broad, dark, conspicuous, median band, and toothed prominently externally; 

 numerous fine, scalloped, more or less distinct, lines on the hind wings. 



This genus differs from Petrophora by the shorter palpi, the pectinated 

 antenna?, or, when ciliated, by the dense cilia, and by the short, thick male 

 abdomen not extendins; as far as the inner angle of the wing, which is some- 

 times distinctly angled. 



There is a good deal of variation in the generic characters given above 

 in the different species, particularly in the condition of the palpi and antennae, 

 as well as in the venation ; but there is much similarity in the markings, and, 

 as a whole, the genus is tolerably easy to distinguish, certainly as much so as 

 some of the genera in other subfamilies; as, for example, the Acidalinai or 

 Geometrlnce. 



Larva. — "Caterpillar elongated, attenuate anteriorly, cylindrical, marked 

 with black points in the incisions; head small and globular; living on low 

 plants. Pupa subterranean." — Guenee. 



