366 Parasites of Common Flies 
were dissected. The tubes were examined daily and the duration of the life 
of the female noted. 
The results are given in Table II. It will be noticed that female No. 3 
was observed to oviposit over a period of 43 days, and produced 7 <J and 325 $, 
and 20 $ nymphs and No. 16 oviposited over a period of 35 days and produced 
4 <$ and 159 $ and 5 nymphs. On the other hand one puparium given to female 
No. 20 contained only 8 $, a puparium given to No. 15 1 S only, and a 
puparium given to No. 16 1 $ and 2 $. 
The first parasites emerged on the twenty-third and the last on the fiftieth 
day after the commencement of the experiment. In one case (No. 2) eggs were 
deposited only in the first puparium which was given, in another (No. 15) only 
in the second out of three lots of puparia given, in another (No. 16) only in 
the second and third out of four lots. In some of the experiments the parasites 
emerged from some of the puparia and were found dead in others. It was 
common to find dead fly remains, without any trace of the parasites, in dis¬ 
sected puparia possibly indicating that the flies had been killed in some 
manner by the puncturing of the puparia. 
In the course of these experiments 36 $ were confined in tubes with 174 
fly puparia and in 35 (20 per cent.) of these puparia the parasites developed, 
and in 2 (1 per cent.) M. acasta larvae on dead A. manducator larvae were 
found. From 52 (29*9 per cent.) of the puparia flies emerged, and from 3 
(2 per cent.) A. manducator . In 76 (43-6 per cent.) dead fly remains and in 
6 (3 per cent.) living A. manducator larvae were found. 
The 33 infected puparia contained 46 <3, 1335 $ and 189 female nymphs, a 
mean of 1 <J, 40 $ and 6 nymphs in each puparium. 
Experiments with virgin females . 
In order to secure virgin females for these experiments infected puparia 
were opened and female M. acasta nymphs removed and placed in tubes till 
they emerged. At varying times after emergence fly puparia were added. 
Forty-one experiments were carried out, and in each only one female was 
employed. To these females 225 fly puparia were given. All those puparia from 
which flies did not emerge were dissected subsequently and the contents noted. 
In eight instances after the removal of the first batch of puparia a second 
batch together with a male M. acasta was placed in the tube. 
From the 225 puparia given to the virgin females 53 (23-5 per cent.) flies, 
6 (2 per cent.) A. manducator and one Ichneumon emerged. 142 (63*1 per cent.) 
contained dead fly remains, 16 (7 per cent.) dead A. manducator and 3 
(1 per cent.) living and 4 (1 per cent.) dead A. manducator larvae. 
In 15 (7 per cent.) of the puparia one or more male M. acasta were found. 
In eleven instances with dead fly remains, in three with dead A. manducator 
and in one with a dead A. manducator larva. Two puparia contained 4 <£, five 
2 <$, eight 1 S • A living M . acasta larva was also found on one occasion with 
dead fly remains. Females were never encountered, and in no case had the 
