INTRODUCTION. xlX 



the sub-median nervure, so as to enclose a space, it is called 

 the interno-median nervule. 



Below the median nervure runs the sub-median nervure (e) 

 which is never branched. Below this again, is the internal 

 nervure (/), which is generally very short, or wanting on the 

 fore-wings. When present, it may either run to the inner maigin 

 near the base, or may unite almost immediately with the sub- 

 median, giving the sub median the appearance of being forked 

 at the base. On the hind-wings it is generally fairly well 

 developed ; and although it is absent in the Papilionidce, in 

 the Pieridce it is generally almost as long as the sub-median 

 nervure ; and indeed, in many species, marked like our Green- 

 veined Whites, a line of colour runs down between these 

 nervures, giving the insects the appearance of possessing three 

 sub-median nervures instead of two. If the term "internal 

 nervure " was not in general use, it would perhaps be better to 

 call these nervures the upper and lower sub-median nervures. 

 The presence of the internal nervure on the hind-wings of the 

 Pierida, contrasted with its total absence in \h.zPapilionidce, and 

 combined with other equally constant and important characters 

 which will be mentioned in their place, seems to indicate that 

 these two groups are sufficiently distinct to be treated as 

 families, instead of as sub-families, as is usually the case. 



ON COLLECTING BUTTERFLIES AND MOTHS. 

 The most useful implement for collecting Butterflies and 

 Moths on the wing is the ring-net. It is a ring of iron, jointed 

 so that it can be folded up, and put into the pocket when not 

 in use. It is made to screw on to the end of an ordinary walking- 

 stick. Neither the ring nor the net should be heavier than 

 needful to give a proper balance in the hand. The ring should 

 be about a foot broad, and the net should be made of green 

 gauze, or some similar material. It should be somewhat 

 tapering, but rounded at the end, not square or pointed, for it 

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