83 



they came out I placed them in a sunny window, and they hecame very active; I then 

 put them upon some hawthorn-leaves, and had very soon the pleasure of seeing them 

 begin to oviposit, which they continued four or five hours. They were so intent upon 

 this, that I could turn the leaves about so as to enable me to see the whole operation 

 distinctly with a Coddington lens. The fly having placed herself in a favourable po- 

 sition upon a leaf, so that her abdomen is in contact with it, raises the cuticle of the 

 side upon which she is (for I found with gathered leaves that she made use of either, 

 but generally the upper), by inserting the ovipositor very gradually, but working it 

 rapidly all the time till it was wholly extended, when it was withdrawn a liquid oozed 

 out, which left the cuticle raised like a little blister, of an oval form, and about the 

 tenth of an inch long : the ovipositor is about a quarter of an inch long. The opera- 

 tion lasts about three minutes, during which the fly lowers her antennae in front, and 

 the segments of the posterior part of the abdomen have a slight tremulous motion. 

 The sight is a most beautiful one, equally as interesting as the ciliary currents of the 

 Rotifera ; the cuticle of the leaf is so transparent, that at a little distance the oviposi- 

 tor absolutely appears to be on the exterior surface. It would seem that although 

 there may be no connexion with the male fly, the desire of propagating their species 

 is equally strong. 



" I would not say that the fly which leaves the cocoou by the small irregular open- 

 ing does so backwards ; it appears strange to me that the skin should be left in the 

 hole with the head of it in the cocoon unless it is so : but I hope next year to see the 

 actual escape of this fly. With regard to the cocoon containing larvae of ichneumon 

 flies, I cannot see what insect made the hole in that cocoon like the others, as it cer- 

 tainly was, if the fly had been destroyed by the parasites, as they did not seem in a 

 state to make it. I inclose one of the cocoons with irregular opening, containing the 

 skin, also one opened by one of my female flies, with the insect and its skin. I hope 

 to find out from some quarter the solution of the difference of these cocoons." 



Mr. Smith observed that he had frequently observed this insect emerge from its 

 cocoon, and always with the head first. 



A paper 'On the Effects of Temperature, Gases, and Vapours on Insects,' by John 

 Davy, M.D., F.R.S., in a letter to Wm. Spence, Esq., was read, giving a detailed ac- 

 count of various experiments, from which it appeared that no two of the agents em- 

 ployed acted precisely in the same manner. Those agents most fatal to life appear to 

 have been sulphuretted hydrogen, ammonia, chlorine, nitric acid, iodine, camphor, oil 

 of turpentine, each varying in degrees of rapidity of effect, but so far analogous that 

 no perfect revival ensued on exposure to the air, after a motionless state had been in- 

 duced. Those less fatal to life appear to have been azote, hydrogen, carbonic acid, 

 coal-gas, muriatic-acid vapour, ether, chloroform ; — all of them producing immobility, 

 and probably insensibility, with different degrees of rapidity, but not commonly termi- 

 nating in death, revival in most instances following. Oxygen seems to stand alone 

 in its effects on the functions of life ; that death sooner occurred in the trial with it 

 than in that with atmospheric air, may have been owiug to exhaustion connected with 

 increased vital action of the insect unsupported by nourishing food. 



