SUBSTITUTION OF A WING FOR A LEG IN A MOTH. 67 



I will now proceed to those cases in which an extra wing 

 exists in an insect, but the usual 4 wings and 6 legs are all 

 present. Such cases have been occasionally recorded, and are well 

 known and authenticated, though not common. I have never 

 myself met with one. I have four of these instances to mention, 

 which are all upon which I have up to the present time been able 

 to get information. 



The first three are described fully in Transactions Entom. Soc. of 

 London, 1879, p. 219, in a paper "On some Unusual Monstrous 

 Insects," by Professor Westwood. 



The first of these is a specimen of the common brimstone 

 butterfly (Gonepteryx rhamni), in which the right-hand hind-wing 

 is double, the fifth or extra wing being affixed at the base of the 

 true wing, which is scarcely more than two-thirds of the natural 

 size, the extra wing being still smaller. Both the right hind-wings 

 are somewhat abnormal in their veining. There were only 5 legs 

 on this specimen, but Prof. Westwood was unable to examine it 

 so as to see if one had been broken off. 



The second case is a specimen of a small tortoise-shell butterfly 

 ( Vanessa urticw). Here the right hind-wing is also double, but 

 the extra wing is much less developed than that of the G. rhamni. 

 The true hind-wing is smaller than the normal size. The supple- 

 mental wing is, in both these cases, affixed at the base of the costal 

 portion of the right hind-wing, but here it is implanted upon the 

 upper side of the wing, and in the specimen of G. rhanmi on the 

 under side. 



In the third case mentioned by Prof. Westwood, that of a male 

 specimen of the common meadow brown butterfly (HipparcMa 

 Janira), a narrow longitudinal strip is, as it were, let in in the 

 middle of the left hind-wing, which, were it not for this strip, which 

 appears from its orange colour and eyelet marking to be a portion 

 of a fore- wing of a male of this species, would be somewhat smaller 

 than the right hind-wing. 



The fourth case is that of a specimen of Saturnia jxivonia, in 

 the possession of Mr. P. 15. Mason, of Burton-on -Trent, who has 



