INSECTA. 819 
labors, collecting honey and wax from sources inaccessible to human means, 
and presents a model of industry and foresight which has often been held up 
by moralists as instructive to man. 
The migrations of insects, or rather their appearance in certain countries, 
at certain periods, laying waste whole territories by destroying the crops, 
and eating up every green leaf and blade of grass, do not seem referable to 
the same causes as the migration of birds and fishes. The appearance of 
locusts (Gryllus migratorius, Lin.) in Barbary, Egypt, and Tartary, and their 
occasional irruptions into the south of Europe, are rather to be attributed to 
the excessive multiplication of the species, from causes favorable to repro- 
duction, than to any periodical, instinctive impulse; and their occasional 
dispersion, in countless numbers, over the neighboring countries, may origi- 
nate in the necessity of finding a supply of food. The direction of their 
flight, in their migration, is generally regulated by the blowing of the wind. 
In places visited with this scourge, the inhabitants eat these insects, either 
using them when recent, or drying and grinding them as a substitute for 
bread. Since the year 1749, though certain parts of Russia, Poland, and 
Hungary are occasionally visited by flights of locusts, Europe has been free 
from any very alarming influx of these animals. In that year, they carried 
destruction over the fairest provinces of Germany, and even extended their 
flight across the Baltic to Sweden. The temperature of the bodies of insects 
is very nearly that of the atmosphere, and thus many of these animals, and 
above all the larve, pass the winter in a state of torpoy. In those which 
live in society, however, such as bees, the temperature of the hive is always 
somewhat higher than the external air. But the temperature which is neces- 
sary to develope one species, is not necessary to all, and hence the distribu- 
tion of insects over the world, in every variety of climate. It has been observed 
that where the empire of Flora terminates, there also terminates the domain of 
Zoology ; for animals which feed on vegetables cannot live in places totally ste- 
rile; and those which are carnivorous must be equally deprived of subsistence. 
Those countries richest in vegetable productions, are therefore the most prclifie 
in insects; and as vegetation diminishes, the number of insects decreases. But 
the proper limits of the different insects in geographical positions, are far from 
heing ascertained; and all that is generally known is, that there are tribes 
peculiar to the warmer regions of the globe, and others that belong to the 
temperate latitudes; that some are extremely local; and that others feed on 
vegetables of extensive dissemination. M. Latreille is of opinion, that, if 
the geographical range of insects were well known, and the species ascer- 
tained, a connection between the vegetable productions of the soil, and the 
animals, might be traced; and aclue might be thence procured for ascer- 
taining from their insect inhabitants, to what portions of the newest con- 
tinents the multitude of islands in the Asiatic ocean originally belonged. 
There is no data for ascertaining with any degree of accuracy the actuai 
number of insects distributed over the surface of the globe. In reference to 
