riERID,E. 23 



observed to reacli land, or have been found in great multi- 

 tudes on the coast, wliere they had evidently just landed. 

 Perhaps one of the most striking accounts is that by Mr. 

 J. E. Kobson of a visitation at Hartlepool, in which the 

 butterllies in immense numbers were coming straight from 

 the direction of the sea, and all travelling steadily towards 

 the north-west continuously for three hours, until stopped by 

 a violent storm, after which they discontinued the concerted 

 migratory movement, and flew about generally. 



Universally distributed, except in the Shetland Isles. 

 Also found in most temjierate regions, extending as far as 

 Japan. 



2. P. rapse, Z.— Expanse, If to 2 inches. Wings of 

 moderate size, white with grey tips, female with two round 

 spots, hind wings yellow beneath. 



Male creamy white, base and extreme apex of fore wings 

 grey, sometimes a more or less distinct black spot beyond the 

 middle. Female varying from creamy white to pale oclireous 

 or much suffused with greyish scales, fore wings having the 

 apex dark grey and two blackish spots beyond the middle, 

 hind wings tinged with grey, and having a costal black spot. 



Under side of fore wings white with greyish-yellow costa 

 and apex and two black spots (in the male occasionally with 

 only one), hind wings rich yellow with a grey shade down the 

 middle, and sometimes suffused with grey scales. Double- 

 brooded— May and July— but actually upon the wing all the 

 summer. 



Variation is in the male mainly in the extent and colour of 

 the apical blotch, and in the presence or absence of a blackish 

 spot above and below; in the female in the colour of the 

 wings, the extent of grey shading, and the size of the spots. 

 The brightest ochreous specimens seem to occur in the south 

 of England in hot seasons, but ochreous and greyish-ochreous 

 forms are found in the north of Scotland and the west of 

 Ireland. The latter locality also furnishes wliite males with 



