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383 
6. Numerous parasites were obtained from naturally infected flv puparia. 
Most of these over-wintered in the puparia. The parasites include numbers of 
the five most important families of the Hymenoptera parasitica or Terebrantia , 
namely the Cynipidae, Proctolrypidae, Ichneumonidae, Chalcididae and 
Braconidae. Infection with species belonging to the last two families is very 
common. 
7. In 1915 great numbers of the chalcid M. acasta emerged from naturally 
infected fly puparia. Experiments and observations on these parasites showed 
that they frequently parasitised puparia already infected with the braconid, 
A. manducator. The males, which are blind, unable to fly and relatively few 
in numbers, reach maturity before the females in the same puparia, and the 
stronger specimens destroy the weaker. The males never leave the puparia in 
which they emerge, but mate with the females before the latter escape from 
the puparia. Fertilised females lay large numbers of eggs from which a few 
males and numerous females develop, but virgin females only lay a few eggs 
from which males develop. If fertilised subsequently numerous eggs are 
deposited from which both males and females develop. These parasites oviposit 
in puparia, but never in larvae. 
8. In 1916 and 1917 N. brevicornis and D. cavus were the chalcids most 
commonly found parasitising fly puparia. 
9. The braconid, A. manducator , was bred very commonly each year from 
fly puparia collected in the autumn. In 1915 61 per cent, of the puparia were 
infected. In each year some of these parasites from the same batch of puparia 
Parasitology xi 
25 
