Aulacigaster leucopeza, our only British member of the genus Aulacigaster (Au-
lacigastridae) has been found on exudations on elm trees (Robinson, 1953). It is a curious, rather
sluggish, shining, brown fly with beautifully banded eyes. The larvae develop in the liquid
exudation and consequently they are adapted to cope with an aquatic micro-habitat and are
equipped with a terminal respiratory tube which is partially retractable.
Adult flies of the genus Odinia (Odiniidae) are also often captured on elm exudations (Collin,
1952). They differ from Aulacigaster leucopeza in that the larvae live in the galleries of
wood-boring beetles. It was thought that the larvae were largely saprophagous. However there
is some evidence that one species, Odinia meijerei is a facultative predator, taking injured or
diseased larvae from the galleries. Odinia hendeli and O. meijerei have been specifically
associated with elm (Benson, 1974). Odinia meijerei has been associated with Elm-bark beetles
(Scolytus spp.); Shillito (1948) recorded this species on elm at Buckhurst Hill and I took it at
Dagnam Park, Romford in the vicinity of some dead elms. Odinia hendeli which appears to be
a rarer species known only from Cambridge (Collin, 1952), Kent (Cogan, 1968) and Essex, has
been recorded from elm. The single Essex specimen, taken by M. W. Hanson in Duck Wood,
Romford in 1989, was from a Horse Chestnut exudation.
The hoverflies (Syrphidae) Ferdinandea cuprea and Brachyopa insensilis are both recorded
from elm exudations.
The yellowish maggot-like larva of Medetera nitida (Dolichopodidae) can be found quite
commonly in the galleries of Elm bark beetles (Scolytus scolytus) (Stubbs and Chandler, 1978).
It has been recorded from neighbouring Cambridgeshire and Suffolk (d'Assis Fonseca, 1978)
and should occur in Essex.
The Soldier Flies (Stratiomyidae) are usually associated with aquatic and sub-aquatic
habitats. A few are also found, as larvae, associated with decaying vegetation. The genus
Pachygaster, a group of small, rotund, black-bodied Soldier Flies is, uncharacteristically of the
family, often found in association with beetle burrows and otherwise under the bark of a variety
of tree species including elm. Pachygaster atra has been found in beetle burrows in elm and
P. leachii has been recorded from decaying elm wood. Both species are not uncommon in Essex,
being swept from elm suckers.
The predatory larvae of various members of the acalypterate family, the Lonchaeidae, are
also to be found under the bark of a variety of deciduous trees including elm.
The Cecidomyiidae (the gall midges), include a number of species specific to Elm - three
gall the leaves, one inhabits the flower buds, one is found under the bark and another is recorded
from a decaying stump (Barnes, 1951). To date I don't know of any specific records for these
very small gall midges from Essex, but they are well worth looking for. The species involved
are: Dasineura ulmicola which produces a small discoloured circular spot on the underside of
the Elm leaf; Janetiella lemei which causes small, rounded swellings on the veins of the leaf on
one side and short tubular or cylindrical outgrowths on the other, and Physemocecis ulmi, which
produces small circular 'pustules' on the leaves 3-4 mm. across dull yellow above and paler
below. The species recorded from elm flowers has not been named. It was recorded from
Yorkshire from Wych Elm but is likely to be quite widespread. The last two species Monardia
ulmaria and Camptomyia corticola are probably the least likely of this group to be found as the
former lives under bark and the latter has only been reared from a decaying elm stump.
The hoverfly (Syrphidae) Pipiza luteitarsis, has been recorded in association with the leaf
curl aphids (Schizoneura sp.) found on elm
(Stubbs in appendix to Stubbs & Falk 1983). M. W. Hanson has a number of records of this
spring species from Epping Forest, but from sites often well away from elm, it may therefore
have larvae predatory on other species of aphid.
The last group of flies to be considered here are those with fungicolous larvae, being drawn
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