Cljc dTanairiau Entomologist. 



VOL. III. LONDON, ONT., OCTOBER, 187 1. No. 8. 



NOTES ON SOME INSECTS OF NOVA SCOTIA AND 



CANADA. 



BY FRANCIS WALKER, F. L. S., LONDON", ENGLAND. 



The following communication is introductory to a few remarks on the 

 Nova Scotian and Canadian Insects which I have received through the 

 kindness of J. M. Jones, Esq., W. Saunders. Esq., and Prof. Croft. 



The study of the geographical distribution of Insects has become 

 more interesting by the difference of opinion as to the origin and diffusion 

 of species. The insects of separate arctic regions have a great mutual 

 resemblance, and the difference between them increases in the successive 

 concentric circles from the above regions towards the equator. It lias 

 been said that the advance of the glacial period was accompanied by the 

 migration of insects southward, and that the present distribution of insects 

 was effected by the prevalance of this epoch and by the succeeding tem- 

 perate epoch. During the diminution of the glacial, the arctic species of 

 the present time migrated northward or ascended the mountains, and thus 

 caused the partial identity of the insects of the Alps with those of the 

 North. The similarity of insects of widely separated regions, such as 

 North Europe, North America, and North-east Asia, chiefly consists in 

 the arctic or northern forms ; the difference between them is found in the 

 species that have advanced northward in later times. Some species inhabit 

 both the South and the North, and occur in Hindostan as well as in 

 North Europe, but the rest appear either to have wholly continued in the 

 South, or to have wholly migrated thence to the North. The insect-fauna 

 of North America appears in two aspects — the northern aspect, which 

 closely and in some cases wholly resembles that of North Europe ; and 

 the southern aspect, which is very different from that of North Europe, 

 and consists of species that have migrated from the South as for as 

 Canada. 



The Diptera in the following list are natives of Nova Scotia, and those 

 marked thus " also inhabit Europe. 



