IMPERFECT SOCIETIES OF INSECTS. 



13 



a leaf ; when hatched, the little larvae feed side by side very ami- 

 cably, and a pleasant sight it is to see the regularity with which 

 this work is often done, as if by word of command ; but when 

 the leaf that served for their cradle is consumed, their society 

 is dissolved, and each goes where he can to seek his own for- 

 tune, regardless of the fate or lot of his brethren. Of this 

 kind are the larvae of the saw-fly of the gooseberry, whose 

 ravages I have recorded before, and that of the cabbage but- 

 terfly ; the latter, however, keep longer together, and seldom 

 wholly separate. In their final state, I have noticed that the 

 individuals of Thrips Physapus, the fly that causes us in hot 

 weather such intolerable titillation, are very fond of each 

 other's company when they feed. Towards the latter end of 

 last July, walking through a wheat-field, I observed that all 

 the blossoms of Convolvulus arvensis, though very numerous, 

 were interiorly turned quite black by the infinite number of 

 these insects, which were coursing about within them. 



But the most interesting insects of this order are those 

 which associate in all their states. Two populous tribes, the 

 great devastators of the vegetable 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 speaking 

 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 produced 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 Professor 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. 

 e( In serene warm weather," 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 



