C. SPRETUS ALWAYS MIGRATORY. 
73 
When Mr. Thoinas begun to study them in the field in 1809, he was 
led to believe from his observations of that season that they are nor- 
mally sedentary, but subsequent investigations have served to convince 
him as well as the other members of the Commission that they are es- 
sentially migratory in their native habitats. 
The evidence upon which this conclusion is founded consists of the 
numerous facts gathered from the various sections of the mountain area, 
showing that year after year they are observed migrating in greater or 
less swarms from point to point within that area. Also the fact that 
in the mountain valleys and canons, during years when there is no gen- 
eral movement, little swarms may be seen rising and flying away to other 
points. Last season Mr. Thomas, while on the top of Pike's Peak, cap- 
tured two or three full-fledged individuals which had probably been 
brought down by the rain of the preceding evening in their attempt to 
pass over, yet no swarm was observed passing during the entire season. 
It is, therefore, evident that their flights do not depend upon numbers, 
but that the brood of a single female, when they attain the proper age, 
will migrate. 
Another fact, which has been repeatedly observed, tends to confirm 
this opinion, to wit, that they do not breed annually over the entire Per- 
manent area. In passing over the mountain section of Wyoming, Col- 
orado, Utah, Idaho, and Montana, we have found it universally the case 
that they are confined to limited districts which are much more extended 
in some years than others. A section infested in one year may be en- 
tirely free the next. That certain favorable points are more generally 
selected as breeding grounds than others is certainly true. 
It is true, there is some evidence which tends to cast doubt upon the 
correctness of our conclusions on this point ; for example, the repeated 
finding of specimens throughout the summer in localities where no migra- 
tions have been observed ; but the flight of a few grasshoppers in these 
sections is so common an occurrence that it is not likely to attract at- 
tention. It is more than probable that many individuals never fly, but 
these are exceptions which do not invalidate the general rule. That 
they are not habitually sedentary in any known locality, as A. american- 
wm is, is certainly a fact that cannot be denied. 
FLIGHTS. 
As the subject of flights is one of the most important relating to the 
history and habits of the migratory locusts, the Commission has taken 
special care to procure all the data possible in reference to the flights of 
C. spretus. Our success in this respect may be seen by referring to our 
former report. That we have exhausted the subject we do not contend, 
but we may fairly claim that now the movements of C. spretus are better 
known to the world than those of any other locust ; and although we 
<lo not wish to appear as boasting, we do feel as we think a justifiable 
pride in asserting the fact. 
