XVI 
PREFACE. 
Eocky Mountain locust is shown to be migratory within the limits of its 
permanent range, and the source of the invading swarms of our own 
species, and the differences, both in direction and character, of return 
swarms, are set forth. These return swarms do little or no injury, and 
the migratory locusts of other parts of the world appear to manifest the 
same disposition to return to the country whence their immediate par- 
ents came, as in the case of our own species. The distance to which 
swarms may migrate in the course of a season, the. position of the insects 
in flight, the influence of the winds on the flights, the height of flight, 
and other questions in reference to the movements of winged locusts, 
whether in this country or abroad, are discussed, as also the causes, 
both remote and immediate, of migration. 
Chapter V, also prepared by Mr. Thomas, deals with the influence of 
meteorological conditions on the development and migrations of locusts, 
as also on the development of the eggs. 
Chapter VI, prepared by Mr. Packard, deals with the subject of the 
southern distribution of Caloptemis spretus, and gives the history of 
locust invasions in New Mexico. 
In Chapter VII Mr. Packard gives a summary of locust flights during 
the years 1877, 1878, and 1879. 
In Chapter VIII, also by Mr. Packard, an accouut is given of the 
western cricket, an insect that proves extremely destructive in the mount- 
ain regions of the West, and about which the Commission has had 
many inquiries. Its ravages, enemies, and parasites, breeding habits, 
and geographical distribution, are set forth, so that they can be com- 
pared with those of the Eocky Mountain locust. Eemedies are sug- 
gested, and the chapter concludes with a study of the external and in- 
ternal anatomy of this large cricket. 
In chapter IX Mr. Packard treats of the air sacs of locusts, with a 
view of indicating their origin, and of showing their use in flight. 
Chapter X, by Mr. Charles S. Minot, is the result of careful histological 
study of the locust, and of the cricket before mentioned. 
Chapter XI, by Mr. Packard, on the brain of the locust, is the result 
of similar study of the nervous system and the brain of the locust. 
Chapter XII, by Messrs. Eiley and Thomas, treats of the destructive 
locust of California, and shows, that while the species is distinct from 
the Eocky Mountain locust, yet in size, habits, destructiveness, and even 
in natural enemies, the two strongly resemble each other. 
Chapter XIII, by Mr. Eiley, gives further facts about the natural ene- 
mies of locusts, and deals more particularly with the locust egg-feed- 
ing habit of the larvae or the Bee-flies (Bombyliidce), a large family of 
two-winged flies, quite abundant in the West, and the larval habits of 
which were not previously known. 
In the closing chapter, XIV, Mr. Eiley has endeavored to present 
more accurate data than had hitherto been given concerning the perma- 
nent breeding grounds, with a view of ascertaining what courses the gov- 
