Habits \ and Power for Injury. 105 



toward the native breeding grounds of the species, and 

 that those which do not so perish reach the Rocky Moun- 

 tain region of the Northwest, whence their parents had 

 come the previous year. They are carried back with favor- 

 ing winds, in thinned and weakened ranks, and those that 

 did not start with the germs of disease, and which escape 

 from other vicissitudes, doubtless succeed in reaching those 

 conditions which favor the continued perpetuation of the 

 species. They do comparatively little harm on the way, 

 and are not, by any manner of means, to be likened to the 

 more disastrous swarms from the opposite direction in the 

 fall. 



