40)4 PHYSIOLOGY. 



propelled at the rate of twenty miles an hour. This carriage was 

 accompanied a considerable distance by a humble-bee (Bombus subinter- 

 ruptus, Kirby), not merely with the same rapidity, but even Avith 

 greater, as it not unfrequently flew to and fro about the carriage, or 

 described zig-zag lines in its flight, in addition to which the wind was 

 against them. Leeuwenhoek relates an instance in which a swallow 

 in a long avenue pursued a Libdiula of the genus Agrion for the space 

 of an hour without catching it*; the little creature continued at least 

 six feet below its pursuer, and at last escaped it. These few instances 

 will convince us of the muscular power of insects. A detailed descrip- 

 tion of their different modes of flight would lead us too far ; we 

 consequently refer to Kirby and Spence's Introduction to Entomology: 

 in the 23rd letter in the second volume will be found an interesting 

 collection of such instances. 



We have as yet cited no convincing instances of the duration of 

 muscular motion, but they are in fact of rarer occurrence than those 

 which exhibit the power and rapidity of flight. Certain phenomena, 

 however, namely, the migrations which certain insects occasionally 

 undertake, prove that even in this view the power of insects is not 

 insignificant. As a wandering insect, the migratory locust is most 

 celebrated. We do not here speak of the devastations that this terrible 

 creature frequently produces, but merely of its flight. This is indeed 

 but slow and heavy, for the locust flies but a short space above the 

 ground, unless opposing objects intervene and cause it to rise higher, 

 yet still of not shorter duration. In their migrations, which, in 1 774, 

 devastated Siebenburgen and Hungary, and which even advanced as 

 far as Vienna, swarms were observed several hundred fathoms thick, 

 one of which occupied four hours in passing a high tower, and thus 

 long at least must every individual have flown. The intelligence of 

 an American newspaper is still more striking-}-, which relates that the 

 ship Georgia, upon its voyage from Lisbon to Havannah, upon the 21st 

 of November, was in the vicinity of the Canary Islands, but yet 200 

 English miles from land. A calm came on, which was succeeded by a 

 light wind from the north-east. Now for the space of a whole hour 

 locusts fell upon the ship and the surrounding sea, which covered its 

 entire surface, yet they were not at all fatigued, but jumped and 

 endeavoured to escape their pursuers. If we even conclude that these 



* Kirby and Spence, Introil. vol. ii. -J- Ib. vol. i. 



