THE CANADIAN ENTOMOLOGIST. 185 
generally to the freshness and newness which they possessed at the close 
of the glacial period. The beginning of the cessation of this period 
_ corresponds with the origin of the present distribution of insect life, or. 
with the commencement of the ascent of the individuals from the tropics 
towards the poles. This is represented on a small scale every year in the 
change from winter to summer, and the two periods of timé agree with 
two aspects of the earth, the transition from the tropics towards the 
_poles, and the upward extent of an alp, the latter being more or less an 
epitome of the former. It may be said by those who do not believe in 
the migration and settlement of insects, that the species were created in 
the districts which they now occupy. In this case it would appear that 
their creation was successive, and that they came into existence more — 
northward and southward in proportion as the glacial climate receded. 
But, as each district became fitted for the maintenance of insect life, 
the inhabitants of the neighbouring district would be ready to occupy the 
vacant ground, and it is well known that the same species of insect often 
occurs in two or more widely separated regions. One species inhabits 
Europe and Chili, and may have migrated from the tropics northward and 
southward as the climate changed. There are indications that the tropic 
land was formerly much larger in extent than it is now, and would have 
afforded space for the multitude of insects which now inhabit the com- 
‘paratively narrow temperate regions. A third explanation of the distri- 
bution of insects is the supposition of the origin of existing species by 
modifications of previous and now extinct organisms. No kind of insect | 
life has been traced back to its beginning, and the blending of species 
which occurs in some genera locally (e.g. the Dipterous genera Laphria 
and Dacus), and which may be interrupted in other genera by the extinc- 
tion of former connecting links, is no proof that each species did not 
first appear in the form which it now assumes, and the blending before 
mentioned represents the oneness and harmony of creation, and the 
unity of its Author. 
The word ‘‘species” is only conventional, to express a difference, 
and there is no proof as to its beginning in two, in a few, or in many 
individuals, or that the differences were not formerly closed up by the 
links which are now extinct. Long periods of time have been described 
in the figures of short and regularly recurring divisions, and thus the 
occurrences therein are more readily comprehended, and in like manner 
the long space of earth and the long extent of time before mentioned are 
