NOCTUINA. 179 



Group 3. NOCTUINA. 



This is a group contrasting greatly with the last, in that 

 its species, though very numerous, are so closely allied in 

 structure and appearance that it is extremely difficult to 

 separate them into well defined and readily recognisable 

 families. Consequently almost every author has a different 

 arrangement, and each classification presents difficulties. 



That of Guenee, which was adopted by my late friend Mr. 

 Stainton in his valuable Manual, is on the whole the most 

 attractive, since by it the group is broken up into sections of 

 moderate extent, and consisting of species which in many 

 respects assort well with one another. Yet it hardly seems 

 to bear a strict examination ; the distinctive characters used 

 to separate families are hardly stronger than those defining 

 genera ; and the so-called sections are very vague, while 

 both seem to be cut to pieces by structural characters of 

 equal importance to those adopted. Indeed, on close exami- 

 nation of the two main divisions, their separating characters 

 as arranged by Guenee, do not appear to hold good. For 

 instance, in the second large division — the Quadrifidce — we 

 find that more than one-half of the species allotted to that 

 group actually possess the trifid arrangement of the median 

 nervure of the hind wings from which the other large division 

 — the Trifidoi — takes its name. Perhaps a slight explanation 

 upon this subject may be useful. The neuration of the fore 

 wings in this group presents no sufficient variation to be of 

 service, but that of the hind wings is more diversified. 

 These organs require in the majority of cases to be folded — 

 once or twice — in order that they may be concealed under 

 the narrower fore wings when the insect is quiescent. The 

 expansion of the wing, as well as its folding, is accomplished, 

 as every one knows, by means of nervures, or veins as they 

 are often called — ribs in fact, like those of an umbrella. 

 These ribs are three in number at the base of the wings, but 

 in the middle area they branch into a number of separate 



