ON THE HOUSE-FLY INVESTIGATIONS. 461 



17. Fly Investigations Reports. — I. Some Observations on 

 the Life-History of the Blow-Fly and of the House- 

 Fi}^ made from August to September, 1915, for the 

 Zoological Society of London. By Winifked H. 



Saunders *. 



[Received March 19, 1916 : Preliminary report read by Prof. H. Maxwell Lefeot, 

 November 9, 1915.] 



The Blow-Fly. 



The breeding-material used was raw meat — a mixture of beef 

 and mutton scraps. The meat was placed in pickle-jars, into 

 which the flies were introduced ; the tops were covered with 

 muslin, and eggs were laid on the meat contained in these traps. 

 The temperature of the room in which they were kept varied 

 from 40-60° F. 



Batches of Bluebottles {Calliphora erythroce2)hala) and Green- 

 bottles {Lucilia ccesar) were watched and compared, and the 

 table given below shows very slight differences in the period of 

 metamorphosis. 



Bluebottle. Greenhottle. 



Ova laid, Sept. lst-2nd. Ova laid, Aug. 24th. 



,, hatched, ,, 2nd-3rd. ,, hatched, ,, 25th. 



Larvae pupated, ,, 14th-19th. Larvae pupated, Sept. 4th-5th. 



Flies emerged, ,, 27th. Flies emerged, ,, 15th-29th. 



As ba.tches of eggs were laid they were isolated, and, so far 

 as possible, the development was watched. The eggs were, as 

 a rule, deposited in little crevices in the meat. The flies are 

 atti-acted to moist meat whether fresh, foul, raw, or cooked, but 

 they avoid dried meat. 



Egg-laying. — -This was observed through a binocular dissecting 

 microscope. A fly which had been isolated in a test-tube with a 

 piece of meat deposited eggs within an hour after being captured. 

 The long ovipositor (about half the length of the body and a very 

 sensitive structure) felt the surface before the passage of each 



egg. 



The eggs which I saw laid were placed parallel with one 

 another, and ari^anged in the typical compact little gTOup. 



In hatching, the eg^g splits longitudinally along a suture mai-ked 

 by a white line. It splits first at the broader end, on the convex 

 side, which is in contact with the dorsal surface of the larva. 

 The rupture is brought about- by the pressure of movement 

 within, and begins with a narrow slit, which lengthens as the 

 maggot escapes. The empty shell very qxiickly shrivels. 



* Communicated by Prof. H. Maxwell Lbfboy, M.A., F.Z.S. 



