250 
LYCAENIDAE 
loses its hold, probably caused by the movements of the 
ants, and the pupa then lies at the bottom of the chamber. 
After remaining as a pupa for about twenty-one days, the 
butterfly emerges and finds its way through the passages in 
the nest to the outer world of warmth and sunlight, when it 
immediately ascends some stem or other object to cling to 
for the expansion of its wings, until fully developed and ready 
to take wing. 
Pupa. The pupa measures 1270 mm. in length. The head 
is rounded ; the thorax is convex and rises dorsally into a 
slight ridge, sunken at the waist; the abdomen is swollen 
and curves to the posterior segments; the anal segment is 
without cremastral hooks ; the wings are ample and swollen. 
The whole surface is minutely granulated and covered with 
very fine, deep amber-coloured reticulations. At first it is 
of a pale, clear, apricot-yellow, which very gradually deepens 
to a dark amber colour, except for the wings, which remain 
light ochreous. The above description applies to the first 
pupa discovered, which I found wild on the surface of the 
ground in a shallow depression under the shelter of a stem of 
Furze, on July 12th, 1905, and from which an imago, a male, 
emerged on July 16th at 8.30 a.m. Previous to this discovery, 
nothing whatever was known of the pupa of M. arion. I 
had, therefore, the gratification and privilege of discovering 
both the larva and pupa of the Large Blue. The larva found 
pupated on June 10th, and the imago emerged on July 1st, 
the pupal state lasting 20 days. 
Imago. The sexual difference is usually distinctly marked. 
The expanse of the wings in the male averages 40 mm., and in 
the female, 44 mm. 
Male . (Upper Side.) The ground colour is a light, silvery, 
iridescent blue. The fore wing has the costal margin narrowly 
edged with white. There is a black lunule at the end of the 
discoidal cell, between this and the outer margin is a curved, 
transverse series of black, wedge-shaped spots, usually four 
or five in number, then an indistinct sub-marginal row of 
spots at the edge of the outer marginal black border. The 
hind wing usually has one or two small median black dots, 
and a sub-marginal series of spots, the outer margin being 
narrowly outlined with black. The fringes are white. The 
