18 



and rivers, by valleys and by plains sheltered by trees. It 

 is impeded by mountains, deserts and the ocean. We have, 

 in North America, essentially one and the same general 

 Fauna, until we reach the Tropical Insular Fauna already 

 colonized in South Florida, and, in- the west, the Tropical 

 Continental Fauna which stretches upward from Mexico into 

 Texas and the South West Territories, while, on the high 

 lands of Mexico, it is probable that members of our Tempe- 

 erate Fauna drift down. Yet the Rocky Mountains, the 

 back-bone of our continent, has influenced a West Coast 

 fauna which, in several cases, has preserved more features 

 of the former Arctic fauna from which the European is also 

 descended. There is a constant flux of species from South 

 to North during the Summer of the year and in this way 

 we have received many tropical visitors whose foothold in 

 our colder climate is more or less precarious and uncertain. 

 The question of wintering comes up, which these summer 

 insects are not accustomed to discuss and cannot practically 

 solve. Hence the Cotton Moth (Aletia argillncea), notwith- 

 standing all its ravages, does not hibernate successfully over 

 most of its territory ; the line of its successful hibernation 

 not having been ascertained as yet and this point in its 

 Natural History, so necessary for the Practical Entomologists 

 to know, is neglected in the Reports I have yet seen. The 

 larvae of the Spliingidae have not yet received a comparative 

 study, although most of them are known; the descriptions 

 should be drawn up commencing with the thoracic segments 

 1 3 ; then abdominal 4 12 ; the head should be described 

 by itself; mere descriptions, however full, without comparisons 

 are tiresome and hard to understand. 



At mid-day the Bee Hawks, Hemaris, may be taken on 

 flowers as well as probably all the Macroglossians with entire 

 wings such as Lepisesia. Those with angulated wings, 

 Ampliion and Thyrens, also in the dusk of evening. I have 

 taken also the higher genera of the following tribe, Deikplnla, 

 Pliilampelus in the day, but the Smerintliini and Spliingini 

 are crepuscular and nocturnal in their habit, so far as I 

 know without exception. There is then a correlation between 



