cxcvi GENERAL SUMMARY OF SCIENTIFIC AND 



tribution of the genus CEneis had been changed from a high 

 northern region to one which may well have included por- 

 tions of the Southern States. And on its decline the ice- 

 sheet drew them back again after itself by easy stages ; yet 

 not all of them. Some of these butterflies strayed by the 

 way, detained by the physical nature of the country, and 

 destined to plant colonies apart from their companions." 



When the main ice-sheet left the foot of the White Mount- 

 ains, some of these CEneis butterflies were left behind. " At 

 a height of from 5600 to 6200 feet above the level of the 

 sea, and a mean temperature of about 48 degrees during a 

 short summer, the White Mountain butterflies {CEneis semi- 

 dea) yet enjoy a climate like that of Labrador within the 

 limits of New Hampshire. And in the case of moths an 

 analogous state of things exists. The species Anarta mela- 

 nopa is found on Mount Washington, the Rocky Mountains, 

 and Labrador. Agrotis Islandica is found in Iceland, Lab- 

 rador, the White Mountains, and perhaps in Colorado. As 

 on islands in the air, these insects have been left by the re- 

 tiring ice-flood during the opening of the Quaternary." 



Some studies by Mr. W. H. Edwards lead him to differ 

 from Mr. Scudder's conclusions in relation to the two 

 broods, vernal and aestival, of two butterflies, Argynnis 

 (Brenthis) myrina and bellona, which were published in the 

 American Naturalist in 1872. Mr. Edwards finds that in 

 Argynnis myrina the butterfly of the fall brood emerges 

 from the chrysalis about the 1st of September, lays eggs on 

 or before the 15th, the larvae hatch between the 20th and the 

 24th, and go at once into hibernation, to awake in May, and 

 reach the chrysalis state about the middle of June, and the 

 butterfly state about the 25th of June. If any of the sum- 

 mer brood of larvae hibernate after their third moult (a 

 fact not established), then the larvae of both broods would 

 awake at the same time and become butterflies at the same 

 time, making the summer brood. It is to be observed that 

 the several stages of the same brood of larvae do not occur 

 in exactly the same periods of time. From eggs laid on the 

 same day, by the same female, some of the larvae hatched 

 will reach the chrysalis state several days before others. In 

 the larger species of Argynnis there will be such a differ- 

 ence, amounting to two or three weeks. Therefore some of 



