THE CANADIAN ENTOMOLOGIST. 71 



margin. The secondaries are usually more or less rounded, shorter and 

 broader than the primaries. 



This is their form in the typical Nodua, but variations from it are 

 numerous ; sometimes the wings are short and broad, again they are nar- 

 row and equal, sometimes lanceolate, and occasionally falcate. In one 

 species only the primaries are divided to the middle, and this is the lowest 

 of our Noctuids, if indeed it belongs to the group. Some genera have a 

 tooth at the hind angle of primaries, some a slight projecting lappet, and 

 others have this angle either rounded or excavated. Little generic value 

 can be given to these variations, as in Pliisia all forms of wings can be 

 found. A lanceolate primary would however indicate a distinct genus, and 

 the same can be said of a decidedly angulated or falcate one. A broad 

 lappet at the middle of the hind margin would indicate a distinct genus, 

 but a merely sinuate hind margin would not. The proportion that the 

 wings bear to each other and to the body, have a high generic value, and 

 genera can be safely rested on that point ; be it understood, however, that 

 I do not mean by this that every difference in that respect authorizes a 

 genus. The proportion must be one striking the eye at first sight, and 

 not to be only discoverable by careful measurement. 



The venatiofi of the wings among the Noctuids varies very slightly, and 

 the variations have been very generally considered as having an absolute 

 generic value. 



The abdomen varies somewhat in shape and proportion, and also in the 

 tuftings. As to shape, it is usually more or less cylindrical, generally 

 reaching to and often exceeding the hind angle of the secondaries ; some- 

 times it is cylindro-conic, as in most Catocala, and sometimes it is flat- 

 tened, as in Scopelosoma and some species of O?rhodia ( Glaea). Its 

 variations of form do not afford good generic characters, nor does its 

 length, unless the proportion is exaggerated. 



The genitaltce of the males vary somewhat, but these variations, while 

 affording excellent specific characteristics, have no generic value. First, 

 because they are sexual merely ; second, because there is an insensible 

 gradation from one into the other, rendering separation impracticable ; 

 and third, because occasionally insects otherwise very closely related, 

 differ very widely in this particular. 



As to tuftings, these vary little in shape, being usually round bunches 

 of vertical hair or scales, varying in number and size. Their presence or 

 absence has no generic value, but aftbrds good specific characters. 



