IMPERFECT SOCIETIES OF INSECTS. IS 



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 nu- 

 merous 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 falling into the water had been brought bapk 

 by the tide ; or whether they had succeeded in the at- 

 tempt 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 ob- 

 servation inclines me to the latter opinion. 



The next order of imperfect associations is that of 

 those insects which feed together : — these are of two de- 

 scriptions — those that associate in their^;-5/ or last state 

 only, and those that associate in all their states. The 

 first of these associations is often vei'y 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, re- 

 gardless of the fate or lot of his brethren. Of this kind 

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

 vages I have recorded before*, and that of the cabbage- 

 butterfly ; the latter, however, keep longer together, and 

 seldom wholly separate. In their final state, I have no- 

 ticed that the individuals of Thrips Physapus^ the fly that 

 causes us in hot weather such intolerable titillation, are 

 » Vol. r. 19/. 



