in Pedujree ^L)tk-hfeedi)Uj. 85 



emergences of illnstraria. — This difference is easily seen, 

 but is perhaps not so easily defined. Besides size and 

 general look, the differences ap[)ear to be mainly these : 

 — (1). The contrast between the outer edge of the dark 

 transverse band and the light ground colour of the part 

 of the wing outside it is generally much stronger in the 

 spring emergence, and, indeed, does not usually exist 

 in the summer emergence. (2). The costa is more 

 rounded in the summer emergence, rarely becoming 

 slightly concave in the outer half of the wing, as it 

 often does in the spring emergence. (3). TheW'ings are 

 longer, narrower, and more pointed, and generally, 

 more angulated in the spring emergence. (4). The 

 outer edge of the dark transverse band on the fore 

 wing of the spring emergence, before it curves, almost 

 always forms an obtuse angle with the line of the costa. 

 beyond it ; in the summer emergence almost always an 

 acute or at most a right angle. (5). The same outer 

 edge, where it approaches the inner edge of the fore 

 wing, generally bends sharply towards the body in the 

 summer emergence : slightly so, or not at all in the 

 spring emergence. [(6). The transparent lunules are 

 generally broader and more conspicuous, when the 

 insect is held up to the light, in the spring than in the 

 summer emergence. (7). The body in the spring 

 emergence is more hairy.] Of all these I think Nos. 1 

 and 4 the most constant. It may here be observed that 

 in both illunaria and illnstraria, and in both emergences, 

 the female is more angulated, and has more pointed 

 wings than the male ; this seems not unusual with 

 those of our Gcometrce which have any tendency to be 

 angulated. 



The variety in markings and colour, and also, I think, 

 in size, I have found much greater in the summer than 

 in the spring emergence [as Prof. Weismann leads us to 

 expect that it would be]. I have endeavoured to increase 

 these differences by selection, and with a beginning of 

 success, as may be seen in the examples I have brought 

 of the extreme forms yet obtained. Some are of a 

 chestnut colour, with few markings above, and of a 

 bright orange, with faint lilac markings beneath. 



Effect of fore in [I on illunaria, illustraria, and ((utitm- 

 naria. — There is a difference of a general kind resulting 

 from the forcing of the larva or pupa, or both, a 



