112 
NYMPHALIDAE 
The inner margin is also bordered with silver and a small 
central costal silver spot. 
The sexual difference is very distinct owing to the thickening 
of the nervures in the wing of the male. The ground colour 
of the female is a paler ochreous-brown, and her under side 
is much more richly marked ; the silver spots are larger and 
those on the apex of the fore wing are usually much more 
developed. The female is also, as a rule, much larger. 
Life of Imago. About four weeks appears to be the life of 
this butterfly. 
Aberration. This butterfly is somewhat liable to striking 
aberration, both as regards the upper and under surface. 
Occasionally, the greater part of the upper side is black with 
only the marginal area fulvous, but with the marginal spots 
missing. On the under surface of the hind wing the basal 
silver spots are confluent, forming one large silver patch, cut 
through only by the nervures, but all the other normal silver 
markings are absent. Between this type of partial melanism 
and the typical A. cydippe , a gradation of intermediate 
aberrations occurs. In very rare instances this species tends 
to albinism. In complete albino examples, the normal black 
markings are all replaced by a delicate pale leaden or pearl- 
grey colour, while the silver spotting of the under side remains 
as informal specimens. In the Tring Museum are two perfect 
examples of this rare type of aberration, both males ; one was 
captured in the New Forest in July, 1901, and the other taken 
in Kent on July 7th, 1888. 
Another type of aberration has occasionally occurred in this 
country. It is known as ab. cleodoxa , having the silver spots 
replaced by ochreous ones, excepting the sub-marginal red 
spots, which are sometimes centred with silver. 
Males with the marginal series of spots ochreous instead of 
silver are of frequent occurrence, but otherwise they are 
normal. 
Argynnts niobc 
Although specimens of this common continental species have 
been recorded as occurring in England, there is no authentic 
evidence to regard it as a British butterfly. 
