32 STEUCTUEE AND LITEEATUEE. 



of the thorax and abdomen on the dorsal line need 

 attention, and for this perfect specimens are requi- 

 site. The wings may have the outer margin scal- 

 loped {Trigo7iophora), even (Conservula), uneven 

 (Brotoloviia), or angulated {Scolioptei^yx). There 

 is a variation in the costal curve, and the apices 

 may be either sharp, pointed, or produced. As a 

 rule the wings are short rather than long ; but in 

 Cleoplicma and CiiculUa, especially the latter, the 

 wings are long and narrow. In approaching the 

 lower group, or Fasciatce, the wings broaden. The 

 veining is usually but little varied. The fore wings 

 have twelve veins, counted on the external and 

 costal margins,' and usually a small accessory cell 

 above and beyond the discal cell. Variations are 

 oifered by the method of branching of tlie sub- 

 costal nervules ; and in a paper published in the 

 ' Canadian Entomologist,' vol. xi. p. 231 et seq., 

 I have discussed these variations in closely allied 

 genera ; they chiefly affect veins 7 to 9. In a few 

 genera the males have an aberrant neuration, and 

 this becomes a sexual character. Such, for instance, 

 is the genus SeliocMlus, found from Alabama to 

 Colorado, and figured by me in the ' Proceedings of 

 the Entomological Society of Philadelphia,' vol. iv. 

 plate ii. figs. 3 6 , 4-5 $ . The subcostal vein is 

 bent downwards, leaving a large space above the 

 discal cell and between it and the costa, which 

 latter is thickened about the centre (see figure of 

 venation, ibid. p. 328). The Southern genus Fterae- 

 tholix, collected by me in Alabama, is also charac- 

 terized by a large pellucid impression near the base 



