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ON THE LARVAL DEVELOPMENT OF DACNUSA 
AREOLARIS NEES (BRACONIDAE), A PARASITE OF 
PHYTOMYZINAE (DIPTERA), WITH A NOTE ON 
CERTAIN CHALCID PARASITES OF PHYTOMYZIDS. 
By MAUD D. HAVILAND, 
Research Fellow of Newnham College . 
. (With 5 Text-figures.) 
INTRODUCTION. 
In the summer of 1921, the Wild Angelica ( Angelica campestris) in the neigh¬ 
bourhood of Cambridge was infested by a leaf-mining fly, Phytomyza angelicae 
Zett. At the end of May and beginning of June, about 60 per cent, of the larvae 
collected were found to contain an endoparasitic Braconid, Dacnusa areolaris 
Nees. No other internal parasite was present, a fact which simplified working 
out the development of this form. 
I must express my best thanks to Prof. J. Stanley Gardiner, who gave me 
facilities for carrying out the work in the Zoological Laboratory at Cambridge; 
and my obligations to Messrs J. E. Collin and G. T. Lyle, who kindly identified 
examples of host and parasite respectively. 
NOTE ON THE BIOLOGY OF THE HOST. 
The larva of Phytomyza angelicae mines into the leaves of Angelica cam¬ 
pestris , forming irregular discoloured blisters on their surface. Usually each 
mine contains a single larva, but occasionally, when the blisters become 
confluent, two or three larvae may be found together. When fully fed, the 
larva leaves the leaf by a slit on the undersurface of the blister, and falls to 
the ground where it pupates. The imagos usually emerge 19-20 days later, 
but the pupal period may be prolonged up to 25 days. 
In captivity, pairing and oviposition took place a few hours after emergence, 
and the flies lived only one or two days. 
THE DEVELOPMENT OF THE PARASITE. 
The Phytomyzid is liable to attack by D. areolaris only in the earliest larval 
stages, when less than 0-5 mm. in length, and older larvae seem to be immune. 
When introduced into a tube with suitable material, the female Braconid 
eagerly explored the upper surface of the leaf until she located a suitable host 
