The picture winged fly Dorycera graminum (F.) (Diptera, Ulidiidae) in South Essex
as well as in the grassland where Hoary Cress was present. The fly was so numerous that I reported
the discovery to Del Smith, the Essex Diptera Recorder, and he met me for a second visit to the site
on 23rd May. Although not especially favourable weather conditions, windy with sunny and cloudy
intervals, Dorycera graminum was found to be the most abundant insect present. Males and females
were present in thousands on the leaves and flowers of Hoary Cress, on yellow Crucifer Barbarea
sp., Weld Reseda lutea and the leaves of Teasel Dipsacus fullonum. On one plant of Weld where
several Dorycera were resting, one male was wing waving, presumably in a courtship display. Of
interest was the large variation in size of both male and female specimens, from 6 to 10mm in
length.
The biology of Dorycera graminum is still uncertain and various possible life histories found in the
Ulidiidae arc discussed by Ismay (2000). The elongate flattened head and elongated body is a
feature of several flies living in the confined environment of grass, rush or sedge stems and there is
some possibility that D. graminum may live in couch-grass Elytrigia sp. (Agropyron) inflorescences.
An association with Umbellifers and Crucifers may simply be related to suitable available forage.
Alexander (1998) reports the discovery of the species at two sites with rank vegetation and
concentrations of Umbellifers, in one case a sheltered lane lined by flowering Hogweed and in the
second from Hemlock Water-dropwort Oenanthe crocata. Clemons (1994) swept the fly from the
lower leaves of Hogweed and from or around Alexanders Smyrnium olusatrum, Clemons (1999)
also reports the discovery of the fly from the lower branches of an elm Ulmus sp. and a stand of
Honeysuckle Lonicera periclymenum in a small area of broad-leaved woodland in Kent at a site
consisting largely of grazing marsh, adjacent to the River Stour. He also reports the discovery of
another individual from Spindle Euonymus europaeus infested with what he presumed to be the
eriophyid mite Eriophyes convulvens at Horton Kirby along the River Darent.
Dorycera graminum appears to have rarely been found in large numbers, the only other comparable
occurrences reported being at Kingsnorth on 13th June 1992 and at Grain on 6lh June 1993, both in
north Kent on the Hoo peninsula (Clemons 1994) and at the Isle of Grain 14th June 1999, where
large numbers were found in an area of land at a partially-worked sand and gravel quarry. Here one
sweep of the net yielded 2-3 flies in some parts (Ismay 2000). The occurrence of the species in very
large numbers at Anchor Field, a site close to the now mostly lost Chafford Hundred localities,
suggests it may represent a core population centre, and an important site at which further research
could be undertaken into the species autecology. Unfortunately the Local Authority is currently
considering the site as development land in the next Local Plan.
My thanks go to Del Smith and Chris Gibson for comments on the draft, and to Del Smith for the
identification and confirmation of Dorycera specimens.
References
ALEXANDER, K. (1998) Two new localities im Dorycera graminum (Fabricius) (Diptera, Ulidiidae).
Diperists Digest (Second Series) 5 (1): 5.
ANON (1996) Biodiversity: The UK Steering Group Report, Vol. 2, Action Plans. HMSO
CLEMONS, L. (1994) Two species of Otitidae (Diptera) circumstantially associated with Umbelliferae
Entomologist's Record and Journal of Variation 106: 138.
CLEMONS, L. (1999) Another note on the occurrence of Dorycera graminum (Fabricius) (Diptera,
Ulidiidae) in Kent. Diperists Digest (Second Series) 6 (2): 92.
FALK, S. (1991) A review of the scarce and threatened flies of Great Britain (parti). Research & Survey in
Nature Conservation, number 39. NCC.
Essex Naturalist (New Series) 19 (2002)
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