PIERIS NAPI. 51 



the centre of the fore-wings, and another in the middle of 

 the costal margin of the hind-wings. The female (Fig. 28) 

 has in addition a second black spot on the fore-wings 

 between the central one and the hind-margin, and a club- 

 shaped mark along that margin, starting from near the 

 second spot and tapering towards the base of the wing. 

 The sexes do not differ on the under-surface (Fig. 30), 

 where the two dots of the female are repeated in both ; 

 the tip of the fore- wings is yellow, and the hind-wings are 

 yellow, slightly sprinkled with black scales. 



P. napi, Linn. (Green-veined White) (Figs. 32 to 36), 

 received its specific name from the Rape, Brassica Napus, 

 which was thought to be its special food-plant, though 

 this does not seem to be the case. A glance at the under- 

 surface of the imago will give a sufficient reason for the 

 bestowal of its common name, except that the veining 

 is often dusky-brown instead of green. It is not easily 

 distinguished from P. rapce on the wing, and probably is 

 not quite so common, as it certainly is not so homely. 



The eggs, which should be sought for in April and 

 May and again in July and August, are laid chiefly on 

 various cruciferous plants, the commonest being Garlic 

 Mustard (Sisymbrium alliaria\ Early Winter Cress 

 (Barbarea prcecox)^ Watercress (Nasturtium offirinale), &c. 

 They are hatched in a little less than a fortnight, and are 

 full-fed during June and September. The imagines result- 

 ing from the early brood come out in July and August, 

 while those from the later appear in the following April 

 and May. P. napi is therefore on the wing almost 

 continuously from the end of April till August. 



The larva (Fig. 34) is of about the same size as that 

 of rapce, and very closely resembles it. The ground-colour, 

 however, is a slightly paler green ; there is no dorsal yellow 

 line, and but one lateral yellow spot in each segment. 



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