The Gall Midges attacking the Seed-heads of Cocksfoot,Dactylis glomerata, L

Abstract

An account is given of four gall midges whose larvae damage the seed of cocksfoot, viz. Contarinia dactylidis (H. Lw.), Dasyneura dactylidis, Metcalfe, Sitodiplosis dactylidis which is described from England and Ireland in the present paper, and Stenodiplosis geniculati, Reuter. The occurrence of predacious midges of the genus Lestodiplosis is also noted.A short section is devoted to characters by which these midges can be distinguished.Stenodiplosis geniculati is recorded from one English and two Irish localities on cocksfoot grass for the first time, hitherto it has always been recorded from foxtail. These midges, together with some experimentally bred on cocksfoot from foxtail parents, exhibit the typical characters of this species.A new variety, Stenodiplosis geniculati var. dactylidis, is described from cocksfoot in New Zealand.In a discussion of the host-plant specificity of gall midges attacking grass seeds, it is suggested that the present discovery of S. geniculati on cocksfoot in England and Ireland and the occurrence in New Zealand of this new variety exhibiting distinct morphological characters are two steps in the evolution of a new species.I am indebted to Miss F. M. L. Sheffield for taking the photographs used to illustrate Plate IV. They were taken to show the comparative lengths of the antennal segments and not the chaetotaxy. I am also indebted to Mr. P. S. Milne who took the photographs used to illustrate Plate V.