June, 1889] . 289 



SUBSTITUTION OF A WING FOE A LEG IN ZYQMNA FILIPENDULM, 

 AND NOTES ON THE YELLOW VAEIETY OF THAT SPECIES. 



BT NELSON M. EICHAEDSON. 



In the summer of 1887 I collected from a chalkpit near Cam- 

 bridge about 700 pupse of Zygcena Jllipendulce, in order to breed the 

 yellow variety of that species which occurred there. I bred a few 

 (five or six, as far as I can remember) yellow ones, and also one 

 specimen with five wings and only five legs : the left hind leg is absent, 

 its place being occupied by a fifth wing. This specimen is a male of 

 the ordinary red colour, of medium size (1" 3^'" in expanse of wings), 

 with the ordinary markings and perfectly developed ; in fact, there is 

 nothing at all unusual about it, except the extraordinary peculiarity 

 above mentioned. The extra wing resembles an ordinary hind-wing 

 of this species in shape and appearance, but is much smaller. It is 

 3'" in length and 2'" in breadth, whereas the hind-wing of this speci- 

 men is 4|"' long by 2\'" broad. The extra wing is much more thinly 

 clothed with scales than the others, being most covered near the base. 

 On the posterior margin of the basal half of this wing there is a 

 distinct blackish border corresponding to that on the hind- wing. There 

 is also a slight blackish border on the basal half of the under-side of 

 the anterior margin. The outer half of the wing has very few scales, 

 and these are mostly of a pale brickdust or brownish-red colour, some 

 being quite colourless and transparent, so that the wing is red at the 

 base, and shades off gradually into a faint brownish-red colour near 

 the tip. The fringe on this outer half is of the colour of the adjacent 

 part of the wing, but with a tinge of grey. 



This wing is attached to the body along the line in which the first 

 joint of the leg would lie if present, and by a junction rather more 

 than 1'" in length ; it would, therefore, probably have been quite 

 immovable when the insect was alive. It has one or two slight longi- 

 tudinal folds, but is not in any way deformed. The wing is inclined 

 to the horizontal at an angle of about 30°, and points downwards and 

 backwards, making an angle of about 45° with the body. 



The area over which this colony of Z.jHipenclulce was spread was 

 not a large one, as they were, so far as my knowledge goes, pretty well 

 confined to the old chalkpit, which was not very extensive. There 

 had probably, therefore, been much interbreeding since the colony had 

 settled down within these limits ; but as it is unlikely that the chalk- 

 pit had been unused and overgrown with herbage for a period reckoned 

 by more than tens of years, I do not think that much weight could 

 be attached to any theory founded on the fact of close interbreeding ; 



