SEASONAL POLYMORPHISM. 



91' 



radial nervures) than the average size of the species (mm. 34 to 88) ; 

 on this account I call it grandis. 



Grade III. : hivittata, Vrty., Ent. Bee, 1916, p. 98, with pattern 

 above as in grade II., but with the grey suffusion at the base of fore- 

 wing also on upperside ; the apical patch is never as reduced in extent 

 as it somtimes is in that grade ; two sharply defined, though narrow, 

 dark streaks across the underside of hindwing. This grade too has 

 a collateral variation consisting in a greater wing-surface, due to 

 broader wings and more convex margins, which make it appear 

 considerably larger, although the expanse is not as much more as one 

 would expect it from the look of the insect. My "types" of 

 bu'ittata are of the second generation, from Mt. Conca, m. 400, 

 above Fontebuona di Vaglia, a cold and damp locality, although 

 not many miles away from the blazing hot Pian di Mugnone, 

 where grandis is produced. The large form of grade III., just 

 described, I propose calling magna, taking as " typical " a little 

 series of the second generation collected by me at the Baths of 

 Valdieri, m. 1875, in the Maritime Alps ; in this locality sinapis, like 

 P. iiapi, actually succeeds in producing a second generation at the end 

 of July, when latJu/ri laggards of the first are still surviving, and a 

 third at the end of August ; the latter consists in form hivittata, with 

 a few diniensis, all strikingly smaller than the second generation. I 

 expect this may be the rule in most Alpine localities, because I have 

 found it in b. Tyrol wherever I have collected. It is interesting to 

 record that the second brood collected by Querci on the Coast Range of 

 Calabria at 900 m., is perfectly identical with the Valdieri one, thus 

 differing, as noted in several species, from the other races of Peninsular 

 Italy, and resembling the Alpine one. Occasionally and more or less 

 frequently, according to localities, one meets amongst the magna with 

 individuals exhibiting very slight or no traces of dark pattern on 

 underside of hindwing ; they difler, notwithstanding, from grandis, by 

 their expanse never being so large, by the broader and convex wing 

 noted in magna, by the presence of the gray suffusion at base, by the 

 apical patch above not being quadrangular nor nearly as extensive as 

 in grandis, although it is usually a little more so in the second brood, 

 and consequently in magna, than in the third one. This individual 

 form, combining the features of magna and those of diniensis, I should 

 deem it useful to designate by the name of magna-uiniensis. In the 

 same way the minority of grandis which have the dark streaks of 

 hivittata on underside might well be called grancis-bivittata. A 

 record of their percentage in the different localities and years will be 

 interesting. 



Grade IV. : transiens, Vrty., Ent Rec, 1916, p. 98, similar in size, 

 shape, and upperside pattern to hivittata, but on underside of hindwing 

 the two dark streaks are more broad, diffused, and shadowed in outline, 

 and the latter gives out projections along the nervures which often 

 connect the two streaks ; a cloud of a lighter gray, because it consists 

 of more sparse dark scales, is seen in some individuals between the 

 streaks and along the dorsal margin ; the ground colour is, on an 

 average, of a brighter yellow than in the preceding grades ; the under- 

 side thus approaches lathgri more or less considerably, whereas the 

 upperside has distinct summer features. I pointed out in my original 

 description that the English summer brood generally consists of this 



