234 [October, 



that this action was undertaken for cleansing purposes, to remove 

 congealed blood that may have oozed from the body of Smynthurus, 

 and collected on the rostrum. Still, it is quite possible that the insect 

 may have been drinking as well, for T have seen a Hydrometra similarly 

 dip its rostrum into the water without having previously partaken of 

 food, but in that case it did not rub its rostrum on withdrawal. I 

 should imagine that the usual food would be the small Diptera and 

 Symenoptera with which the leaves of the Potamogeton swarm, and 

 that this is the reason for their selecting these leaves as their usual 

 head-quarters. But whether they catch their prey alive, or avail 

 themselves of the numerous drowned or partially disabled specimens 

 that are sure to be found lying about, I cannot say, since the supplies 

 I gave them consisted only of freshly killed insects, and the difficulty 

 of seeing them on the pond prevented my deciding the matter by 

 watching them in the open. 



Mesovelia is scrupulously cleanly in habits. The specimens I was 

 observing, when first put into their jar, were incessantly busy cleaning 

 themselves. Each leg on either side rubs its next neighbour on that 

 side ; the fore pair also clean one another in the manner with which 

 the house-fly has made us familiar. With the fore-legs also the insect 

 cleans its antennae and rostrum, drawing the antennae between the two 

 tarsi, and then running the latter down the rostrum, taking great care 

 that the tip of that instrument is thoroughly cleaned. With the 

 second and third pairs of legs they clean the back, by rubbing the 

 tarsi over the surface. When the above toilet had been gone through, 

 I occasionally saw them bob down and bring the under-side in contact 

 with the surface on which they were resting, but whether this was 

 with a view to cleansing, or some other reason, I cannot say. I do 

 not think Mesovelia ever voluntarily goes below the surface, and, in 

 fact, they would probably find it a difficult matter to do so. When a 

 specimen was purposely submerged, it rose at once, but experienced 

 some difficulty in getting above the surface again, on account of the 

 fluid tension, which required a struggle to overcome, but when once 

 up, there was no further difficulty, and it at once set to work to brush 

 itself down with its tarsi. Hydrometra does not get so easily over a 

 like experience. A specimen of this insect when submerged found 

 the greatest difficulty in emerging from the water, its hair-like legs 

 drawing out a thin film of water as it thrust them above the surface, 

 and when it had at last got clear, and apparently escaped from the 

 troubles of capillarity, it was unable for some hours to venture safely 

 on the water again ; each time that it attempted to do so, its tarsi 



