IMPERFECT SOCIETIES OF INSECTS. 297 



Bombay, as he was playing at chess one evening with a friend in Old 

 Woman's Island, near that place, witnessed an immense flight of bugs 

 (Geocoris<B) which were going westward. They were so numerous as to 

 cover every thing in the apartment in which he was sitting. When staying 

 at Aldeburgh, on the eastern coast, I have, at certain times, seen innume- 

 rable insects upon the beach close to the waves, and apparently washed up 

 by them. Though wetted, they were quite alive. It is remarkable, that 

 of the emigrating insects here enumerated, the majority for instance, the 

 lady-birds, saw-flies, dragon-flies, ground-beetles, frog-hoppers, &c. are 

 not usually social insects, but seem to congregate, like swallows, merely 

 for the purpose of emigration. What incites them to this is one of those 

 mysteries of nature, which at present we cannot penetrate. A scarcity of 

 food urges the locusts to shift their quarters, and too confined a space to 

 accommodate their numbers occasions the bees to swarm ; but neither of 

 these motives can operate in causing unsocial insects to congregate. It is 

 still more difficult to account for the impulse that urges these creatures, 

 with their filmy wings and fragile form, to attempt to cross the ocean, and 

 expose themselves, one would think, to inevitable destruction. Yet, 

 though we are unable to assign the cause of this singular instinct, some of 

 the reasons which induced the Creator to endow them with it may be con- 

 jectured. This is clearly one of the modes by which their numbers are 

 kept within due limits, as, doubtless, the great majority of these adventurers 

 perish in the waters. Thus, also, a great supply of food is furnished to 

 those fish in the sea itself, which at other seasons ascend the rivers in 

 search of them : and this probably is one of the means, if not the only one, 

 to which the numerous islands of this globe are indebted for their insect 

 population. Whether the insects I observed upon the beach, wetted by 

 the waves, had flown from our own shores, and fallinginto the water had been 

 brought back by the tide ; or whether they had succeeded in the attempt 

 to pass from the continent to us, by flying as far as they could^ and then 

 falling had been brought by the waves, cannot certainly be ascertained ; 

 but Kalm's observation inclines me to the latter opinion. 



The next order of imperfect associations is that of those insects which 

 feed together : these are of two descriptions ; those that associate in their 

 first or last state only, and those that associate in all their states. The 

 first of these associations is often very short-lived : a patch of eggs is glued 

 to a leaf; when hatched, the little larvae feed side by side very amicably, 

 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 fortune, regardless of the fate or lot of his brethren. Of 

 this kind are the larva? of the saw-fly of the gooseberry, whose ravages I 

 have recorded before, and that of the cabbage butterfly ; the latter, how- 

 ever, 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 Convol- 

 vulus 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 



