106 Geographical Distribution of Insects. 



of the latter, and may even go so far as to put almost a com- 

 plete stop to it, in localities of an insulated description. In 

 the last century, the inhabitants of the Isle of France intro- 

 duced a species of Alcedo or kingfisher, to destroy the locusts 

 which ravaged their plantations, and these birds freed them 

 from the evil in a short time. They had even a considerable 

 effect on the entire entomology of the island. 



Enemies not less numerous nor less formidable are to be 

 found in their own class. Not only do the carnivorous spe- 

 cies devour each other, but many of those which are phyto- 

 phagous feed their larvae with other insects. This is probably 

 the reason, at least in part, of the preponderance of certain 

 families over others. May we not, for example, to a certain 

 degree, account for the multitudes of phytophagous coleoptera 

 in intertropical countries, by referring to the limited number 

 of carabida; which exist there .'* 



There is still another way in which insects exercise influ- 

 ence on each other, by modifying their stations. In our la- 

 titudes, the carabidae, vdth very few exceptions, Uve on the 

 surface of the ground. In equatorial America, on the con- 

 trary, the greater part live on trees. This appears to arise 

 from the innumerable legions of ants which have taken pos- 

 session of the soil, and constrained them to take refuge on ve- 

 getables.* 



Finally, man himself is not without exercising a great in- 

 fluence on insects, both with regard to their habitation and 

 stations. He has transported them either voluntarily or with- 



* The cause here assigned by M. Lacordaire for the difference in ques- 

 tion, scarcely seems satisfactory, for, even though adequate to produce the 

 alleged effect, its operation must be confined to particular localities. It 

 must doubtless be sought for less proximately in the benign ordination by 

 which every animal is adapted to the circumstances in which it is destined 

 to exist. In countries so densely clothed with vegetation, the expansive 

 and almost continuous foliage forms the platform on which insects live, ra- 

 ther than the surface of the ground, which is frequently in deep shade, and 

 therefore uncongenial to their nature. The habits of tropical carabidae are 

 therefore primarily and necessarily arboreal, because it is on trees that they 

 find theii- appropriate food. No change of condition in the soil itself could 

 change the habits of the carabi of northern latitudes so far as to make 

 them frequent trees, because they are often apterous, and otherwise un- 

 fitted for such a mode of life. 



