HABITS OF TWO PARASITES OF BLOW-FLIES. 



213 



approximately half of the length, and consist of soft dirty white 

 integument roughly in folds. 



Length of Feriocl of Oviposition. — Females, whether freshly 

 emerged or otherwise, and which had or had not mated, once 

 allowed to oviposit, wei'e dead the next day if they had been 

 constantly ovipositing, or when resting and feeding occa^sionally 

 lasted three to four days ; in one instance a female lived five days 

 ovipositing in about 50 larvae daily. 



Progeny of IS ingle Females. — No extensive data were obtained 

 on this point, but in the laboratory the average was 33'74 per 

 female. (See Percentage of Parasitization.) 



Parthenogenesis. — Unmated females reproduced males ; whether 

 the latter were fertile was not investigated. 



o 



Proportion of the Sexes. — This appears to be about equal on 

 the whole in individual lots of material parasitized in the 

 laboratory, although one sex may considerably predominate. 

 The figures given under this heading are details of emergence 

 from three lots of material which were parasitized by free 

 Braconids in Regent's Park, and give the follow^ing result : 199 (5" 

 and 294 $ . No other details of emergence from outside material 

 were compiled. Graham-Smith (4) gives, substantially, the 

 following details for " Spring " and Autumn " batches which 

 emerged in 1916 from material parasitized in the autumn of 

 1915. The sum total for both batches are 2891 S and 749 $, 

 •clearly indicating arrhenotokie, a proportion, which the writer 

 ventures to suggest may, in this instance, be due to the immediate 

 proximity of host-infested carcases when the females of the 

 autumn batch of 1915 emerged. 



Length of Life of Adult. — In the laboratory the length of the 

 life of adults was not very long. Observations show^ed that, in 

 the case of two freshly-emerged males which were not permitted 

 to mate, one lived 25 days, the other 31 days ; two unfertilized 

 females not allowed to mate or oviposit lived 33 and 38 days ; 

 two females and two males confined together, the former not 

 being allow^ed to oviposit, the males lived, the one 18 days, the 

 other 23 days ; the females, one 25 days, the other 33 days. And 

 as stated oviposition rapidly ends the female's life. In each of 

 the foregoing tests ample supplies of food were given, but the 

 insects were confined in glass jars, which did not give much 

 opportunity for fiight and the atmosphere was permeated with 

 the odour of carrion. The length of life in the open or in 

 unpolluted air would doubtless be longer. 



The length of life within the main cage appeared to be much 

 shorter during the months of November, December, and January 

 in spite of a mean temperature of 20° C. Activit}^ was always 

 greatest on fine days, and particularly wdien the sansliine was 

 directly upon the cage. 



Food. — When the breeding operations began, the adults were 

 fed on sugar diluted with water in a ratio of 1 to 5, but owing to 

 the " Rationing Uestrictions," honey had to be substituted, and 



15* 



