March, 1917.] FORBES : HyDRIOMENIN^ OF THE UNITED STATES. 57 



Mdcv. of hind wing bent, though short, wings acute, ace. c. at end of discal cell. 



lignicolorata. 

 Mdcv. of hind wing straight, wings rounded, ace. cell before end of discal cell. 



obscurata. 



16. To judge by the South American fauna Eudule is one of a 

 considerable group derived from Stamnodes or a closely similar form, 

 in fact the genera seem to intergrade through CEiiotrus. In some of 

 these the wings are practically normally scaled, but may be distin- 

 guished from Stamnodes, etc., by the characteristic single large ac- 

 cessory cell. Typical Eudule has small hind wings and the abdomen 

 extending well beyond them. Typical examples are E. pidchricolora, 

 venata and invqxia (of which nigricosta and our species unicolor 

 appear to be synonyms). E. helveta is transitional to group Eupha- 

 nessa, whose pattern it shows. Mennis is a further exaggeration in 

 the same direction where the body exceeds the wings by a fourth its 

 length (bimacida, ficidnea, cythena, una, fidentia, bipcnnis, leopar- 

 dina, orsUochia and sceata were seen). These two groups have a 

 distinct tendency to enter mimicking associations. Our eastern 

 species (mcudica and mcridiana) , with short bodies and ample hind 

 wings belong to group Euphanessa, from which group Leptidule, of 

 South America differs in the strongly tufted fore wing with dis- 

 torted venation (L. medca, didcifera). 



17. There is a strong tendency in all parts of the world for arctic- 

 alpine species of all families to show these characters. In South 

 America such forms have developed from Stamnodes, and from its 

 black-marked variant, Heterusia; in North America Euchxca shows 

 the same tendenoy, for from genitalic characters this is where " Hy- 

 driomena" rubrosuffusata belongs. It is also very doubtful if our 

 species of Trichochlamys are really close relatives. Hagnagora 

 (catagrammina and buckleyi of South America) is easily recognized 

 by its much enlarged tympanic opening and blue-marked hind wing. 

 Bombia also has hairy vestiture and simple antennae; both wings are 

 broad and somewhat lobed at middle of outer margin, and there is a 

 single large ace. cell connected with Sc. Heterusia is the South Amer- 

 ican representative of Stamnodes distinguished by the larger area of 

 black, the usually squarer wings, and the strong tendency to develop 

 frontal hair. Our 5". albida is in all except its lighter coloring, a 

 Heterusia. H. edmondsii of Chili carries the hairiness to the extreme. 



