J. T. Wadswortti ]r.'j 



the dipterous larvae prcsont in the flower-heads, by inducing gall- 

 formation, caused a reduction in the number of the seeds normally 

 produced by this troublesome and useless weed, which is very common 

 in many pastures and meadows. 



A number of the infected heads were brought to Manchester, and 

 kept until the following spring, when, towards the end of June, imagines 

 commenced to emerge from the galls, and continued to do so during 

 the ensuing three weeks. 



The fly was recognised as a Trypetid and specimens for determination 

 were submitted to Mr J. E. Collin, of Newmarket, to whom I am indebted 

 for naming them ; they belong to one of the common species of Try- 

 petidae, viz. Urophom fiohlifialis L. Mr Collin also informed me that 

 so far as he knew the larvae and pupae of this species had never been 

 scientifically described. 



Early in July some young flower-heads of the knapweed were 

 gathered and a few fertilised female flies were placed on them in a covered 

 glass jar. The females deposited eggs freely, and in eight days from 

 the date of oviposition free larvae were observed within the flower-heads. 

 It was thus apparent that the flies would breed freely in captivity, 

 and Professor Hickson suggested that I might undertake a study of 

 the life-history of this species. 



The work was carried out in the Department of Agricultural Ento- 

 mology of the Victoria University, Manchester, and I wish here to thank 

 Professor S. J. Hickson for his kindness in providing me with opportu- 

 nities by which I have been enabled to undertake thi.s research ; to 

 Dr A. D. Imms my thanks are also due for valuable suggestions and 

 advice given during the later stages of its progress, and to Professor 

 F. E. Weiss for permission to use apparatus belonging to the Botanical 

 Department. My indebtedness to others who have assisted me in 

 various ways, is acknowledged in the text. 



Description of fly and classification. 



The fly was described by Linnaeus (1758) under the name Mitsca 

 solstitialis ; since then it has been frequently referred to and more 

 fully described, under various names, by several entomologists. Loew 

 (1844) discussed the characteristics of this species very fully, and he 

 recognised and described five well marked size and colour varieties. 

 In his monograph Die europaischen Bohrftiegen (1862) the same author 

 gives a full description of the species, together with the synonomy ; 



