[ 185 ] 
VI. On two Aquatic Hymenoptera, one of which uses its Wings in Swimming. 
By JOHN LUBBOCK, Esq., E.R.S., F.L.S., F.G.S. 
(Plate XXIII.) 
Read May 7th, 1863. 
ON one of the early days in August I was enjoying myself by watching the animals in 
a basin of pond-water. It is customary to regard the inhabitants of fresh water as less 
beautiful and varied than those of the sea. But though our inland lakes and rivers can 
boast no Sea-anemones, no Starfishes, Medusz, Shrimps, nor Sea-urchins, they still are 
full of beauty and variety. Without counting the rarer forms, almost every weedy pool 
contains specimens of Daphnia, Cyclops, Diaptomus, and Asellus among Crustacea, the 
Hydra among Polypes, the lovely green Volvox, and many other Algæ, besides numerous 
Desmidie and Diatomacese, with Insects almost innumerable. Besides the perfect 
insects, such as Water-beetles, Notonecta, epa, and other Hemiptera, there are larvee of 
Dragon-flies, Beetles, Phryganeas and Ephemeras, the beautifully transparent larvee of 
Corethra and many other species of Diptera. But though most of the great orders are 
more or less richly represented, no aquatic species of Hymenoptera* or Orthopterat had, 
till now, been discovered. The species of Hymenoptera have been estimated at about 
30,000 in number, and Mr. F. Smith (than whom thereis no better authority) informs me 
that about 12,000 have been already described, 3500 of which live in Great Britain. 
From the interest attaching in many cases to their habits, from their marvellous instincts, 
and their curious relations to other animals (no order presenting more parasites and 
victims of parasites), the peculiarities of Hymenoptera have received more attention 
than those of almost any other group of Invertebrata. 
Great therefore was my astonishment, on the occasion to which I allude, when I saw 
in the water a small Hymenopterous insect, evidently quite at its ease, and actually 
swimming by means of its wings. At first I could hardly believe my eyes; but having 
found several specimens, and shown them to some of my friends, there can be no doubt 
about the fact. Moreover, the same insect was again observed, within a week, by another 
entomologist, Mr. Duchess, of Stepney. This gentleman mentioned it to Dr. Sclater, 
and, from his description and sketch, there can be no doubt that the insect observed 
* The female of Agriotypus armatus, indeed, has been observed to descend the sides of rocks in the = a 
considerable depth, and to remain there several minutes. Even this species, however, cannot be considered as truly 
aquatic, or as being entirely at home in the water, since there is no evidence that it knows how to swim. : 
Mr. Smith also reminds me that Smiera (Chalcis) femorata and S. sispes are said to be parasitic on the aR 
larvee of Stratiomys, in which case the perfect insect probably seeks its prey under water; but I am not aware that 
it has been actually observed to do so. | : 
+ A “ Grillon sme " is indéed described by Stoll ; but Westwood, in his excellent ‘ Introduction to the Modern 
Classification of Insects,’ expresses some doubt as to the accuracy of this statement. : 
A 
