INSECTS. 



that year they carried desolation 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 larvae, 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 necessary to develope one species is 

 not necessary to all, and hence the distribution 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 sterile ; and those which are carni- 

 vorous must be equally 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 races of in- 

 sects in geographical position 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 ascertained, a connection be- 

 tween the vegetable productions of the soil and the animals 

 might be traced ; and a clue might thence be procured for as- 

 certaining from their insect inhabitants to what portions of the 

 nearest continents 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 to the plants upon which they feed, De- 

 candolle conjectures, that 60,000 species being already known, 

 the total number of plants may extend to from 110,000 to 

 120,000. And Messrs Kirby and Spence, reasoning on this 

 calculation, and that several insect inhabitants are often found 

 upon the same plant, conjecture that 400,000 insect species 

 may exist on the surface of the globe ; and, proceeding on the 

 same data with regard to the plants of this country, that the 



