,]. T. Wadsworth 140 



males than females emerged, but towards the end of the month, this 

 disproportion in the sexes was decreased. Fitch observed that the 

 males emerged before the females, but he only obtained twelve females 

 and eight males ; the numbers he dealt with are therefore very small. 

 If the results obtained above should be confirmed by subsequent count- 

 ings of greater numbers, they might be explained by supposing that 

 the greater numbers of males produced and their early emergence are 

 provisions for ensuring that as far as possible, all the females shall be 

 fertilised. 



Four days after emergence, two pairs of flies were observed in 

 copulation, and another pair copulated five days after they emerged 

 (June 5th and Gth). Probably several days intervene between copula- 

 tion and oviposition, the exact length of time that elapses between these 

 two acts was not determined. 



When the female is ready to oviposit she selects an unopened bud ; 

 the bracts of this, however, are just beginning to open. If the flower- 

 bud is suitable for the purpose, she is observed to move over it in various 

 directions ; at the same time the ovipositor is frequently protruded 

 and inserted at various points between the bases of the scales ; she is 

 evidently selecting a suitable place for the insertion of her ovipositor. 

 As soon as this is found she settles down, her head pointing towards 

 the apex of the bud ; the first joint of the ovipositor is then bent almost 

 at a right-angle to the abdomen, and pushed between the bases of the 

 lowest and outermost scales ; whilst in this position the ova are placed 

 within the flower-head. 



If a flower-head which contains eggs is severed vertically into two 

 halves, and carefully examined, the eggs will be found either in the 

 space between the upper surface of the florets and the overlying bracts 

 (Fig. 2) or betw^een the florets themselves. In order to understand 

 how the eggs are placed in these positions, the ovipositor, during the 

 process of oviposition, may be rapidly severed from the abdomen with 

 a sharp pair of fine scissors, and its position in the flower-head observed ; 

 or in a fortunate section of an infected flower-head the tunnel made 

 by the passage of the ovipositor may be seen (Fig. 13). Evidence has 

 been obtained by both these methods, and in order to explain the 

 process of oviposition in a more complete manner, a short description 

 of the ovipositor is inserted here. 



The female fly possesses the usual corneous, pointed, three-jointed 

 ovipositor which is characteristic of the three closely related families 

 of acalypterate muscids, Trypetidae, Ortalidae and Lonchaeidae (Bezzi). 



