99 



which controls this tendency, and this factor is probably ot 

 considerable importance to the well-being and preservation of 

 the species. 



Mr. Tutt remarked that the rarity of a partial third brood 

 of P. napi in Britain was to be noted. It was a most 

 unusual occurrence, and possibly only took place in very 

 suitable summers, and then only in very occasional 

 individuals. There was perhaps a tendency for some fifty 

 per cent, of the summer-feeding- larvae to emerge in late 

 summer, the rest going over the winter. In P. brassicce a 

 still smaller proportion of second- and third-brood specimens 

 emerged, although in P. rapes a very large proportion of the 

 partial second and a fair proportion of the partial third brood 

 emerged. The occurrence of these individuals was always 

 worth noting in reared broods. 



As to the point raised by Mr. Main on the difference 

 between the pupae of summer- and spring-emerging speci- 

 mens, Mr. Tutt observed that it was a well-known fact that 

 the larvae of Anthocharis bclia collected in the south of 

 Europe in the spring gave rise not only to two forms of 

 pupae of different colours but also of different structure (the 

 summer-emerging pupae having one movable incision, the 

 others none) , and so far as the seasonal broods of these species 

 varied generally in size and form, so, of course, must there 

 be a corresponding variation in the pupal size and form, more 

 or less readily distinguishable by the expert. The winter 

 pupae of P. napi were said to be narrower, and usually more 

 heavily marked with black, whatever was their ground colour. 



The relation of the number of broods or partial broods to 

 latitude and altitude was also very interesting. At high 

 latitudes and altitudes the species was single-brooded, no 

 doubt in the extreme south of Europe, almost entirely double 

 with a large partial single brood. In Britain, in bad seasons 

 the species was almost entirely single-brooded (as were many 

 other partially double-brooded species), in favourable seasons 

 more complete and partially double-brooded. Among each 

 brood were individuals, "laggards" from the commencement, 

 and totally incapable of being forced into a second brood, 

 whilst others were just as certainly "forwards," and could 

 not be restrained ; the greater mass, however, apparently 

 were capable of responding directly to environmental 

 conditions. Merrifield noted, in his experiments in 1893, 

 certain individuals that refused to be forced in each of the 

 batches he dealt with. Mr. Joy had bred one example that 

 insisted on going over two winters as pupa. 



