140 Mr. F. Merrifield's systematic temperature 



The deaths were very few, apparently not more than 

 would have occurred if the pupse had not been iced ; 

 there were no cripples, and the moths emerged with 

 such perfect regularity that when the temperature in 

 which the pupa was placed after removal remained 

 about the same, I could always foretell within a day 

 when the moth would emerge. 



Effect on colour and markimis. — As might have been 

 expected, there is no change in size, but I am not sure 

 there is not a slight difference in form caused by the 

 icing, in a less rounded costa and a rather narrower 

 wing. The difference in colour, however, is great, and 

 in markings striking. In colour a general warm brownish 

 hue with a considerable increase of darkness prevails. 

 One of the most striking differences between the ordinary 

 summer and spring form is in the shape of the outline 

 of the dark inner portion of all the wings. In the 

 summer form this outline approaches a half circle, but 

 is very sinuous, with a conspicuous break of continuity 

 where it passes from the anterior to the posterior wing, 

 caused by curves inwards, and with several angles, of 

 which the most salient is on the anterior wing, near the 

 costa, with the outer portion of which it consequently 

 forms an acute angle. In the spring form the dark 

 inner portion approaches the shape of a lialf hexagon, 

 the most salient angle being on the posterior wing, the 

 other angles and curves being straightened out, an 

 obtuse angle being substituted for the acute angle on the 

 costa, and the outer edge of this dark part becoming 

 continuous from the anterior to the posterior wing. 

 This edge is also more blurred in the iced than in the 

 uniced specimens. The first appearance of these changes 

 in markings was in a female iced 28 days, and after 56 

 days they became frequent in both sexes, a male of 

 20 weeks' icing and two females of 18 weeks' seeming 

 the most marked. As may be gathered, the change is 

 not a gradual and regular one from fortnight to fort- 

 night. Still there are some intermediate specimens 

 that appear to show the i)rocess of transition — an 

 interesting subject for investigation, which, however, I 

 must leave to those who are better qualified to jnirsue it. 

 I think it is of consequence to observe that the moth 

 from the iced summer pupa, though there are chauges 

 causing it to bear a considerable general resemblance to 



