SOME CECIDOMYIDAE ATTACKING THE SEED OF DACTYLIS QLOMERATA L. AND LOLIUM PERENNE L.

SUMMARY. 1. Three species of Cecidomyidae have been observed destroying grass seed on the Park Grass Plots at Harpenden: two species attacking Dactylis glomerata, and the third L. perenne. Of the two species on D. glomerata one has been identified as Gontarinia dactylidis (H. Lw.), the other is described for the first time as Dasyneura dactylidis sp.n. The species present on L. perenne is also a new species and is described as G. lolii sp.n. 2. All three species of midges are single brooded at Harpenden, the larvae overwintering in the soil. D. dactylidis emerges between May 21st and June 6th, C. dactylidis between June 3rd and 24th and C. lolii between May 31st and June 26th. The damage is done by the larvae which feed on the ovary, singly in the case of D. dactylidis, collectively in the other two cases. Parasitism by certain Hymenoptera in 1932 was respectively 42–3, 11–6 and 0–75 per cent. 3. It has not been found possible to cause attack by C. dactylidis on F. rubra or L. perenne. Similarly no infestation by C. lolii was produced on F. rubra, Dactylis glomerata or Alopecurus pratensis. It appears probable that these gall midges are specific in their attack. 4. In a brief discussion of control methods it is suggested that delaying the flowering of the grasses either by grazing sheep or by clipping, or by very early cutting to prevent the development of young larvae, might prove effective.