6 LFPIDOPTF.RA. 



at least, but in many species for weeks or months, and even 

 in some instances for years, with this peculiarity, that however 

 long it may so remain after the first year, it will only produce 

 the perfect insect at that season in which it would have made 

 its appearance if perfected in the first year. This emergence, 

 whenever it takes place, is the last of the series of changes of 

 skin, and the comparatively inert and shapeless object breaks 

 open at certain defined lines or sutures, and so allows the 

 perfect insect (imago) to escape. The creature is now perfect 

 so far as the organs of the head and the legs are concerned, 

 but the body is somewhat distended with fluid, and the wings 

 are totally useless and imperfect, being mere soft flaps of very 

 small size close to its sides, but having the shape, markings, 

 and generally the colour of the developed wings. When the 

 colour is different it arises from the fact that the tips of the 

 scales — the only portions then visible — are of a different 

 colour from their surfaces. Thus, in Thccla ruhi the un- 

 developed wings are of a golden-brown beneath, although 

 they become green as they expand. This expansion in most 

 species takes place in a few minutes, or at any rate in less 

 than an hour after emergence, and is caused by the fluid in 

 the body being forced into the nervures and between the 

 membranes of the wings, and, if the insect be undisturbed, 

 full extension is soon reached. Then, after the wings have 

 hung loosely for a short time to gather strength, they are 

 usually raised from the sides and placed perpendicularly (as 

 regards the insect) from the back, still, however, being kept 

 as far as possible pendant, until comparatively dry and firm, 

 when they are brought to their ordinary position and are 

 soon ready for use.- Occasionally, and for no apparent reason, 

 a moth will defer the expansion of its wings for hours or even 

 until the next day. 



Species varj as much in the duration of theii" perfect state 

 as in the earlier stages, except that life in the perfect con- 

 dition is never known to exceed a year. Probably this length 

 of existence is very nearly reached by some of those species 



