INSECTA. 819 



labors, collecting honey and wax from sources inaccessible to hviman 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 migratortus, 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 tliem 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 m.any of these animals, and 

 above all the larva;, pass the winter in a state of torpor. 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 beequally deprived of subsistence. 

 Those countries richest in vegetable productions, are therefore the most prolific 

 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 

 being 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 a clue 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 actual 

 number of insects distributed over the surface of the globe. In reference lo 



