THE WHITE LETTER HAIRSTREAK. 145 



female agrees in colour with the male, but the tails are longer, 

 and there is no sex mark on the fore wings. The under side is 

 brownish, with a white line on each wing, that on the hind 

 wings forming a W before the inner margin ; the hind wings 

 have a black-edged orange band on the outer margin which is 

 finely tapered towards the costa. Captured specimens are 

 usually browner than those that are reared from caterpillars. 



The species does not exhibit much tendency to variation. 

 The white lines on the under side may be rather broad or very 

 narrow, and that on the hind wings is sometimes so broken up 

 towards the inner margin that the W character disappears ; 

 when absence of the anal orange spots on the upper side is 

 associated with the broken line, the form is known as butlerowi. 

 I have several males without the W, and some of these have 

 the orange spot above, whilst others are without it. Barrett 

 refers to a specimen in which there is "on the under side 

 an extension of white colour from the white line towards the 

 margin, in the fore wings forming a broad wedge-shaped band, 

 but in the hind wings occupying the whole space from the white 

 line to the orange band." 



The egg has been described as whitish in colour, and in 

 shape something like an orange with a depression on the top. 

 The eggs are laid on twigs of elm in July, and, according to 

 some writers, remain thereon throughout the winter. The 

 caterpillar when full grown is yellowish-green and covered with 

 short hairs ; the ridges on the back are yellowish, and there are 

 oblique whitish streaks on each side of the darker dorsal line. 

 The head is black. When about ready to assume the chrysalis 

 state, the whole body becomes purplish-brown. The chrysalis 

 is brownish, sometimes tinged with purple ; covered with tiny 

 bristles except on the blackish wing cases, and there are two 

 purplish lines on the back. It is attached by the tail, and has 

 a strand or two of silk around it, generally on the under side of 

 a leaf. 



