290 
PIERIDAE 
ground colour of the male is milk-white ; a grey cloud extends 
along the basal half of the costa, and a short, darker grey 
dash along the base of the inner margin of the fore wing ; 
at the apex is a large oblong grey or black blotch, also usually 
two blackish streaks along the nervures below the blotch. 
The hind wings are white, faintly clouded with pale grey, 
caused by the under side markings showing through the wing. 
( Under Side.) The fore wing has the under side clouded 
with pale grey similar in pattern to the upper side, with the 
apex more or less tinged with lemon-yellow. The hind wing 
is clouded and streaked with grey, forming two curved trans¬ 
verse bands. Sometimes the whole of the ground colour is 
tinged with lemon-yellow, producing a greenish-grey hue. 
Female. The female has the fore wings broader and more 
rounded than the male, and generally the apical spot is less 
developed, often consisting only of pale streaks along the 
nervures. 
Life of Imago. The natural duration of life of this delicate 
little butterfly is probably about fifteen days. 
Aberration. In the second brood the males have the apical 
blotch smaller and usually blacker; the females have the 
markings more or less obliterated, and sometimes entirely 
absent. Such examples are wholly of a milk-white colour 
above, and almost entirely white below'. This white form 
is known as ab. erysimi. 
A striking albinistic aberration of this butterfly was captured 
in Monmouthshire on May 22nd, 1914, having all the normal 
markings replaced by ochreous-buff. 
