298 IMPEKFECT SOCIETIES OF INSECTS. 



in all their states. Two populous tribes, the great devastators of the vege- 

 table world, the one in warm and the other in cold climates, to which I have 

 already alluded under the head of emigration you perceive I am speak- 

 ing of Aphides and Locusts are the best examples of this order : although, 

 concerning the societies of the first, at present we can only say that they 

 are merely the result of a common origin and station; but those of the 

 latter, the locusts, wear more the appearance of design, and of being pro- 

 duced by the social principle. 



So much as the world has suffered from these animals, it is extraordinary 

 that so few observations have been made upon their history, economy, and 

 mode of proceeding. One of the best accounts seems to be that of Profes- 

 sor Pallas, in his Travels into the Southern Provinces of the Russian Empire. 

 The species to which his principal attention was paid appears to have been 

 the Locusta Italica, in its larva and pupa state. " In serene warm wea- 

 ther," says he, " the locusts are in full motion in the morning immediately 

 after the evaporation of the dew; and if no dew has fallen, they appear as 

 soon as the sun imparts his genial warmth. At first some are seen running 

 about like messengers among the reposing swarms, which are lying partly 

 compressed upon the ground, at the side of small eminences, and partly- 

 attached to tall plants and shrubs. Shortly after, the whole body begins to 

 move forward in one direction, and with little deviation. They resemble a 

 swarm of ants, all taking the same course, at small distances, but without 

 touching each other : they uniformly travel towards a certain region as fast 

 as a fly can run, and without leaping, unless pursued; in which case, in- 

 deed, they disperse, but soon collect again and follow their former route. 

 In this manner they advance from morning to evening without halting, 

 frequently at the rate of a hundred fathoms and upwards in the course of 

 a day. Although they prefer marching along high roads, footpaths, or 

 open tracts, yet when their progress is opposed by bushes, hedges, and 

 ditches, they penetrate through them : their way can only be impeded by 

 the waters of brooks or canals, as they are apparently terrified at every 

 kind of moisture. Often, however, they endeavour to gain the opposite 

 bank with the aid of overhanging boughs ; and if the stalks of plants or 

 shrubs be laid across the water, they pass in close columns over these tem- 

 porary bridges, on which they even seem to rest and enjoy the refreshing 

 coolness. Towards sunset the whole swarm gradually collect in parties, 

 and creep up the plants, or encamp on slight eminences. On cold, cloudy, 

 or rainy days they do not travel. As soon as they acquire wings they 

 progressively disperse, but still fly about in large swarms." 1 



" In the month of May, when the ovaries of these insects were ripe and 

 turgid," says Dr. Shaw 2 , " each of these swarms began gradually to dis- 

 appear, and retired into the Mettijiah, and other adjacent plains, where they 

 deposited their eggs. These were no sooner hatched in June, than each of 

 the broods collected itself into a compact body, of a furlong or more in 

 square, and marching afterwards directly forwards toward the sea, they let 

 nothing escape them they kept their ranks like men of war ; climbing over, 

 as they advanced, every tree or wall that was in their way ; nay, they en- 

 tered into our very houses and bed-chambers, like so many thieves. A day 

 or two after one of these hordes was in motion, others were already 



Pallas, ii. 422426. Travels. 187. 



