76 REPORT UNITED STATES ENTOMOLOGICAL COMMISSION. 
move northward, as was the case in 1867 and 1874, and to a large extent 
in 1876. Experience has now also enabled those who have carefully 
studied their characteristics to distinguish, in most cases, " invaders" 
from those hatched in the temporary regions. A corresponding fact in 
the case of A. peregrimtm will hereafter be noticed, where the difference 
in color alone is sufficient to distinguish between the invading and 
returning swarms. In the case of C. spretm the difference in color is 
slight, the most marked being the somewhat fiery red of the pronotum 
in the invaders; and the position of the wings in repose presents also a 
variation. Practice and experience will even enable those who have 
never paid any attention to the study of entomology to distinguish 
between the two. 
The first supposition, which appears very plausible, fails also, in part 
at least, when we test it by the facts. In the first place, the intermediate 
plains where he swarms would have todevelop are so frequently traversed 
now by stockmen that the fact of their presence would be communicated. 
In the second place, it is now a well-ascertained fact that locusts hatched 
anywhere in the temporary region south of the southern line of Dakota 
-almost always move northward when they begin to fly, whereas the sup- 
position requires them to go south or southeast. Thirdly, as we know, 
from positive data, the returning swarms from as far south as Texas 
reach Western Dakota and even into Montana, it is therefore highly 
probable that the invading swarms extend their flight in a single season a 
like distance southward. Lastly, the facts ascertained, although showing 
some exceptions, warrant the general conclusion as we have stated it.* 
As illustrating this, we present the following facts in reference to 
1875 and 1876, the former being considered a year of " returning swarms" 
from the temporary region, and the latter a year of " invading swarms" 
from the permanent region. Most of the facts stated will be found scat- 
tered through our former report. 
1875. — In Texas a swarm arrived at Eagle Pass from the north in 
September, " but north of this State up to the United States boundary 
line there was no general invasion from the northwest." 
In Indian Territory locusts hatched out this year in large numbers, 
and "during the month of May they departed in a generally north and 
west direction." Large numbers flew westward. 
In reference to Kansas, the record states that " the locusts hatched 
jout mostly in April and early May, and became fledged May 28 to June 
15, and then all flew in a general northwest direction,*' and that "there 
were no invasions from the north or west that year." 
The same thing was also true in reference to Nebraska, but some of 
•the swarms which flew north in June appear to have returned southward 
in August, the diseased condition of the latter showing that they had 
^evidently been hatched in the temporary region. 172 
172 See Appendix, pp. 129 and 130, First Report, 
Note. — Facts recently ascertained appear to somewhat modify this conclusion. 
