NOTE ON TKl*: blVICRSlUN OF THE FTIEINUM 



DURINC; THE EMERGENCE OF TFiE HOUSE FLY, 



MUSCA DOMESTICA, LINN. 



By CiiAKLKs William Mallv. M.Sc. F.E.S., F.L.S. 



( )n niakiiiii; a critical study of the publislied descriptions of 

 the transformations of the House Fly. Musca domestica, Linn.. 

 I found diver^^ent statements as to how the eversion of the 

 ]>tilinum during the emergence of the fly was brought about — 

 some specify that air is forced into it, and others that blood is 

 forced into it. From my own observations I felt sure that the 

 eversion was due to a liquid being forced into it. 



To test the matter, house fly puparia were placed in a small 

 glass tube plugged with cotton wool. As the flies forced their 

 way past the cotton wool sufficiently to expose the everted 

 ptilinum it was punctured by means of a needle. A droplet of 

 clear yellowish liquid at once came forth. This was repeated 

 with numerous flies, and always with the same result. As soon 

 as the j)tilinum had been punctured the flies remained helpless 

 between the glass and the cotton wool. 



This shows clearly that the eversion and the introversion of 

 the ])tilinum is due to the liquids in the body being driven alter- 

 nately forward and backward by alternating muscular contrac- 

 tion and expansion, the ccmtraction beginniny' in the posterior 

 part of the abdomen. 



\\'hen the flies which had been subjected to the Oj^eration, 

 which 1 shall de.''ignate ptiUnal puiictuyc. were isolated in clean 

 glass tubes plugged with cotton wool, they remained alive and 

 active for days — practically as long as normal unfed flies — but 

 the wings did not expand, neither did the mouth])arts nor the 

 sexual organs come to perfection. The flies became darker in 

 colour, l)ut otherwise they remained in the condition they were 

 when the ])tilinnm was punctured. 



AN ACCOUNT OF THE CHIEF TYPES OF VEGETATION 

 IN SOUTH AFRICA; WITH NOTES ON THE PLANT 



SUCCESSION. 



Bv Prof. ToHN William Bews, M.A., D.Sc. 



(Printed in journal of Ecology, Vol. 4. Nos. 3 & 4, Dec, 1916.) 



COMMERCIAL AFFORESTATION IN SOUTH AFRIC.V. 



By Thomas Robertson Sim. 



(Not printed.) 



