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XIII. A Preliminary Catalogue of British Cecidomyidae 

 (Diptera) ivitli special reference to the Gall-midges 

 of the North of England. By Richard S. Bagnall, 

 F.L.S., and J. W. Heslop Harrison, D.iSc. 



[Read May 2nd, 1917.] 



For many years the Cecidomyidae, a family of Diptera, 

 famiKar enough to naturahsts in a cursory sort of way 

 (because it embraces the httle flies known as " Gall- 

 midges "), has been neglected by British entomologists, in 

 spite of its extent and great economic importance. 



Of its members a considerable proportion are purely 

 gall-causers, each producing its particular gall on its 

 host-plant or plants. These galls are characteristic of the 

 species and are therefore part of its specific characters, but, 

 unlike many such distinctions, they can be thoroughly 

 rehed upon as a means of determining the species. They 

 are not, as many entomologists unacquainted with their 

 stability think, unworthy of consideration ; such an 

 opinion simply displays ignorance on the part of its 

 holder. 



Any one taking up the study of the group in real 

 earnest will soon find that many do not fall into the 

 category of genuine gall-makers. Their modes of life are 

 exceedingly varied, and thereby render the subject the 

 more interesting. Some feed as larvae under bark, in 

 decaying wood, in stems of grasses, sedges, fungi and 

 mosses; others, again, find their food in epiphytic fungi 

 such as rusts, smuts and mildews. We find still more 

 figuring as commensals and inquilines in the galls of 

 Cynijndae, Gall-midges and other insects, and also of the 

 Gall-mites (Eriophyidae), whilst others have larvae ecto- 

 parasitic or predatory on Aphididae, and Eriophyid and 

 other mites. Of the remainder, a small number are 

 Endoparasites, the larvae living in the abdomens of certain 

 Hemiptera {Aphididae, PsylUdae and Tingidae). 



Some of the Lestreminae, like tliose of the genus Miastor, 

 reproduce their kind by paedogenesis, and are of extreme 

 TRANS. ENT. SOC. LOND, 1917. — PARTS II, III, IV. (MAY '18) 



