SCIENCE-GOSSIP. 



89 



AN AQUATIC HYMENOPTEROUS INSECT. 



By Fred. Enock, F.L.S.. F.E.S. 



7 NDER the above head in the " Transactions of 

 the Linnean Society " (vol. xxiv., 1864, page 

 135, etc., plate 23) will be found an interesting 

 account of the capture of Polynema nutans (Lubbock), 

 by Sir John Lubbock, who mentions that on examin- 

 ing a basin of pond water, he was astonished to see a 

 number of minute hymenopterous insects swimming 

 about in the water, and using their wings for that 

 purpose. Within a week of this grand chance 

 capture, another specimen was found by Mr. 

 Duchess, of Stepney ; then nineteen years after 

 (1881), Mr. Bostock found a single specimen in a 

 bottle of pond water at Stone, Staffordshire. 

 Since 1876, I have paid particular attention 

 to this interesting family, the Mymaridae or 

 Fairy-flies, and though I have searched many 

 ponds, year after 

 year, all my efforts 

 to obtain specimens 

 of P. nutans have 

 been unsuccessful. 



On Saturday, 

 May 4th, at the 

 fortnightly excur- 

 sion of the members 

 of the Quekett Mi- 

 croscopical Club, 

 which was to Totte- 

 ridge and Mill Hill, 

 Mr. Wm. Burton, 

 brought home two 

 small phials of 

 water, containing 

 various organisms. 

 The first to appear in the trough was a small fly, 

 which appeared quite at home climbing about the 

 weeds. Mr. Burton, knowing my weakness for 

 these small creatures, kindly brought it to me for 

 examination, when I immediately recognised it as 

 the long-sought-for P. nutans, this capture making 

 the fourth time it has been taken by chance. 



On Monday, May 6th, Mr. Burton and I, started 

 out to search for more specimens. We dipped our 

 nets and bottles in and out for over two hours 

 when my dip brought to land a beautiful female, 

 which I quickly transferred to a phial. Then in 

 the course of a few hours more search, I found four 

 males. On reaching home, these, together with the 

 female, I put into an observation tank, where they 

 remained under -water for over four days, swimming 

 or flying through the water in the most lively 

 manner, their progress being decidedly jerky. The 

 female was chiefly engaged examining the flocculent 

 matter at the bottom of the lank, no doubt search- 



POLYNEMA NATANS, X 15 DIAMS. 



Drawn from life by Fred. Enock 



ing for eggs in which to oviposit. I now have 

 several fresh specimens under close observation 

 during day and far into night, and in course of 

 time hope to complete the life-history of this 

 marvellous creature. 



It is much to be regretted that so very little 

 interest has been taken by entomologists in this 

 most extraordinary family, the Mymaridae, which 

 have scarcely been noticed since the death of Mr. 

 Haliday, whose type collection has remained in 

 oblivion. When this collection is brought to light, 

 I am inclined to think that the generic name of 

 Polynema with regard to nutans will prove to be the 

 wrong one, as the male of that genus has thirteen 

 joints in the antenna, whereas the male P. nutans 

 has but twelve, and the abdomen is distinctly 



petiolated so that 

 it cannot belong (as 

 suggested by the 

 late J. O. West- 

 wood) to Anuphes, 

 whose abdomen is 

 subsessile. 



Strange as the 

 habits are of many 

 parasitic Hymen- 

 optera, they are 

 completely eclipsed 

 by those of the 

 Mymaridae. The 

 fact has now been 

 fully established, 

 that the females 

 lay their eggs in the 

 eggs of other insects. Polynema nutans (according to 

 Ganin), ovipositing in those of dragon-flies. I have 

 repeatedly watched Alaptus wandering over leaves in 

 search of the eggs of Psocus faseiatus and on finding 

 them, she gently taps one with her heavily clubbed 

 antenna? to ascertain whether the egg already 

 contains a parasite, if not, she leisurely mounts on 

 the top, pressing the tip of the tiny ovipositor 

 against the convex surface, the boring machinery 

 is set in motion, and in about two minutes a hole 

 is pierced and an egg transmitted by the Alaptus in 

 so perfect a manner that nothing is injured. The 

 microscopic aperture is hermetically sealed by 

 saliva from the tongue, and the fairy-fly steps on 

 to the next egg until the whole cluster has been 

 " struck," and all chance of an injurious Psoeus 

 emerging has been destroyed. I hope the time is 

 not far distant when we shall have figures of all the 

 known genera of this most interesting group. 

 21, Manor Gardens, Hollouay, London, V. 

 May 13th, 1895. 



