106 [May, 



at frequent intervals, began to fly away. Those which came on shore 

 either crawled back or rose with difficulty. They generally took one 

 or two turns in the air before they finally departed, and at times it 

 looked as if a swarm of bees was flying about, their flight being not 

 unlike that of bees, but rather slower. T'hey finally flew off, rising to a 

 considerable height, all in an easterly direction towards the Weymouth 

 Backwater, about 1| miles distant, but whether that was their destina- 

 tion (it is brackish water) or not, it is impossible to say. The number 

 that left the pond must liave been very large, for the exodus lasted 

 for certainly two hours and probably longer ; it had quite ceased by 

 2.30 p.m., and I estimated the rate of departure as being often as 

 many as from one to two hundred in a minute when the sun shone 

 brightly. Some thousands must have left the pond akogetlier, far 

 more than I should have imagined it contained. A great many fell a 

 prey to the starlings which were hawking about in an unusual manner 

 in considerable numbers at a little distance, in the line of flight of 

 the insects. A few (perhaps 20 or 30) large water beetles (Acilius 

 sulcatus, Linn.) came to the edge of the water and sat on sticks, &c., 

 which projected above its surface, and some crawled up the mud, but 

 we only saw four actually fly away, so that the migratory impulse did 

 not seem to be so strong upon them as on the boatmen. I did not 

 see any other insects migrating, unless it were one or two small 

 beetles, but I am not sure about these. 



Nothing unusual appeared to be going on in the adjacent pond 

 to the west, wliich is generally well populated and also a permanent 

 pond. There was hardly any wind, none at all being perceptible on 

 the pond, but what there was came from the west, and it was a rather 

 warm day for the season. Under ordinary circumstances one sees a 

 few of the water-boatmen occasionally in the pond, but they never 

 seem to be particularly numerous. 



No further migration from this ])ond was observed until 

 October 1 1th, when, between 11 and 12 in the morning, the day 

 being warm and sunny, another smaller species of " water-boatman " 

 {Gorixa fahricii, Fieb.) was seen to be migrating in considerable 

 numbers, though not to the same extent as the larger species in 

 September. They continued tmtil about 2 \).m., when the flight 

 ceased. They did not swim to the edge of the pond like Corixa 

 gcoffroyi, but seemed to rise straight from the bottom and fly up from 

 the surface of the water. They then circled round higher and higher 

 until they were lost among the branches of the surrounding trees ; 

 but some, after taking a turn or two over the water, flew straight 



