102 BRITISH BUTTERFLIES AND MOTHS 



The expansion of the wings is from 2^ to 3^ inches. 

 The brilliant bluish-purple gloss is peculiar to the male, 

 and is only visible when we look at the wings in a par- 

 ticular direction ; a specimen which appears at one 

 moment of a most brilliant purplish-blue will the next 

 instant seem of a dull blackish-brown ; the fore-wings 

 have three small white spots near the tip, five others 

 placed nearly in a curve from the middle of the costa to 

 near the anal angle, and a white band in the centre 

 half-way across the wing ; in the hind- wings the central 

 white band is continued across nearly to the anal angle, 

 where the colour of the wing becomes fulvous ; between 

 the white band and the hind margin, near the anal 

 angle, is a black spot in a fulvous ring. 



The curious-looking larva is pale green, with oblique 

 yellow lines, and a yellow stripe on each side ; the 

 head bears two green tentacle-like horns, whence the 

 larva, which is very stout in the middle and much 

 attenuated towards the tail, has been not inaptly com- 

 pared to a green slug ; it feeds in May and at the 

 beginning of June on sallows and poplars. 



The perfect insect appears in July, and soars on the 

 tops of oak-trees. Occasionally it descends lower down 

 so as to come within the reach of the collector, but 

 unless we resort to stratagem it is not easy to obtain a 

 series of this handsome insect. The dead stoats, weasels, 

 etc., nailed by gamekeepers to the sides of barns, are 

 found to be a favourite repast with the Purple Emperor, 

 and when these happen to be placed in a wood frequented 

 by Apatura Iris, a goodly number will descend to regale 

 on these delicacies. In 1857, one collector captured 

 thirty-seven specimens in two days by this means. 



