THE WHITE LETTER HAIRSTREAK 
281 
serrated hairs of various lengths. There is great individual 
aberration in colouring. Most specimens have the ground 
colour a clear, light greenish-yellow, with the medio-dorsal 
and the side oblique stripes and lateral ridge, pale yellow; 
the ventral surface and the claspers are green. Others are 
less green in colour and variegated with rose-pink markings 
on the fourth and ninth segments. When ready for pupation 
the larvae turn duller in colour, the yellows and greens change 
to brown-olive and ochreous hues. 
The young larvae feed on all parts of the Elm blossom 
and grow rapidly. As they grow, they attack the buds and 
young leaves, but are especially fond of the former, which 
they perforate by boring into them, only half their bodies 
remaining exposed. Often they completely devour the whole 
of the interior, leaving only a thin outer covering. The 
larval stage occupies about forty-five days. 
The larva of this butterfly has no cannibalistic habits 
whatever during any stage. 
In a wild state this species pupates on both surfaces of 
the leaves of the Wych Elm, also, and more frequently, 
attached to a twig at the fork and among a few of the samara 
(winged fruit) spun around it; these closely harmonise with 
the. colouring of the pupa. 
Pupa. The pupa is stout in proportion to its length and 
measures 9 mm. long. The head and thorax are rounded ; 
the abdomen is swollen at the middle and rounded posteriorly ; 
the ventral surface is straight. The whole of the anal ex¬ 
tremity is amply furnished with hooks. The ground colour 
is pale ochreous-brown; the head purplish-black; the 
wings heavily blotched with deep purplish-brown, almost 
black ; a black band passes over the thorax and first two 
segments; the sides of the abdomen are sprinkled with 
dark brown specks. The thorax and abdomen are covered 
with finely-pectinated whitish bristles, and the whole surface 
with a network of reticulations and minute lenticles. The 
pupa is firmly attached to a layer of silk by the cremastral 
hooks and a cincture round the waist. The pupal state lasts 
twenty-six days. 
Imago. The sexes are easily distinguished by a small, pale, 
oval spot of androconial scales at the end of the discoidal cell 
