120 THE CANADIAN NATURALIST. [Vol. viii. 



Union are concerned, in his Seventh Annual Report, to which 

 my information could only enable me to add a few particulars. I 

 therefore present here in a summary form the facts collected 

 from the region lying north of the forty-ninth parallel, as a con- 

 tribution to the history of the invasion of the summer of 1874, 

 and a slight addition to the general knowledge of the locust and 

 its migrations. 



My thanks are due to the gentlemen who have kindly answered 

 the questions addressed to them, and especially to those who 

 have furnished me in addition with general results of their 

 experience. 



It now seems certain that the locusts causing such widespread 

 damage on the western plains, belong to a single species, known 

 to entomologists by the name of Caloptenus spretus. For its 

 description, Prof. Thomas' Synopsis of the Acrididae, or Mr. 

 Riley's report above mentioned, may be referred to. The locust 

 is a native of the high and dry western portion of the interior 

 plain, and not of the alpine vallies of the Rocky Mountaius, as 

 at one time supposed. North of the forty-ninth parallel, the 

 whole area of the third, or highest prairie-plateau, and probably 

 much of the second, are congenial breeding places, and here the 

 locusts are always in greater or less numbers, but in certain 

 seasons they sweep eastward and southward in immense hordes, 

 reaching to, and even beyond the limits of the region of prairie. 

 In range, the insect is not bounded westward by the Rocky 

 Mountains, save where they coincide with the eastern unbroken 

 front of the western forest region, as in British America. They 

 extend southward at times to the Raton Mountains, and iuto 

 Texas, while to the east they have spread to the prairie country 

 of the Mississippi, and on more than one occasion have penetra- 

 ted far into Iowa. Northward, they appear to be limited by 

 the margin of the coniferous forest which opportunely follows 

 the line of the North Saskatchewan River. 



It is difficult to ascertain exactly what the causes are which 

 lead, or drive the locust in certain years to leave its western 

 habitat, though it is possible that simply an excassive increase 

 in numbers may bring about that result. Only a mere fraction 

 of the vast multitude of eggs deposited can under ordinary cir- 

 cumstances come to maturity, and their vitality and the survival 

 of the young insects, may depend on so many circumstances, 

 climatic and otherwise, that even on the above simple supposi- 



