Essex Elms - Their Associated Flora and Fauna
This chapter is devoted to the plants and animals that have been found on elms in Essex. I have
divided the chapter into six sections, each of which has been contributed by a member of The
Essex Field Club. The limited space available in the booklet has not permitted a wider spectrum
of groups to be included.
1) Introduction. Mr. M. W. Hanson
Insects exploit a wide range of micro-habitats on elm trees including the leaves, flowers, fruit,
decaying wood, bark and wet-wood wounds. A few, such as the White-letter Hairstreak
butterfly, are specific to elm. Others are commonly found on elm but will also be found on
other tree species.
The most pertinent association of insects with elm are the bark beetles Scolytus multistriatus
and Scolytus destructor, the carriers of the fungal pathogen that causes Dutch Elm Disease.
Both species are known from Essex and presumably are extremely common. Another beetle
Aulonium trisulcum found in Hatfield Forest (Rackham, 1988) predates the larvae of Scolytus
spp. under elm bark.
Bacterial wet-wood is a common infliction of East Anglian Elms. Here a watery liquid oozes
from a fissure in the bark of the tree. This 'flux' is attributed to a bacterium Erwinia
nimipressuralis (Rackham, 1975). The exudation, although apparently toxic, is attractive to
many species of insect as a feeding medium for adults and larvae. Much of the literature referring
to insects at elm tree trunk wounds calls such feeding sites 'sap runs', which may be incorrect.
A sap run and a bacterial wet-wood exudation are two completely different things.
J. F. Shillito (1947) records insects from numerous orders visiting such an exudation in
Roebuck Lane, Buckhurst Hill. Shillito records the species erroneously as Wych Elm. Of
particular interest Hornets (Vespa crabro) up to a maximum of twelve were noted at any one
time; Rose Chafer (Cetonia aurata) and the local bug Anthocoris gallarum-ulmi were also
recorded. Two butterflies, the Comma and Red Admiral, were noted feeding at the exudation.
Miller Christy (1918) mentioned a number of elms (identified as Ulmus glabra Miller,
presumably Ulmus minor. East Anglian Elms) 'a dozen or twenty of them' lining the drive
leading up to his house at Chignal St. James. The trees were large and ancient and one of the
trees, about 85 ft. high and 4 ft. in diameter, regularly produced an exudation which attracted
wasps, hornets and flies. Miller Christy added that the phenomenon was well known in elms
especially, in his district, to woodmen, hedgers and farm labourers.
In Essex the gall mite (not an insect) Eriophyes campestricola is abundant on English Elm
suckers. I have also found what I assume is the same species on East Anglian Elm (on sucker
leaves and mature tree leaves) and on Hybrid Elm sucker leaves. From Wanstead Park I have
found one leaf of Wych Elm with what are apparently the pimple galls of this or a related species.
From the Hatch Grove, Western Sewage Farm site I made a number of collections and
observations of insects on the leaves of the various elms here. I found roll galls of Eriosoma
ulmi and a single specimen of the bizarre gall of Tetraneura ulmi. This gall is rugby-ball shaped,
about in. long and attached by a long petiole to the surface of the leaf; yellowish patches occur
on the upper surface of the leaf around the gall stalks point of attachment and groups of 'hairs'
on the lower surface of the leaf in the same area. Also from this site I swept a number of
specimens of the rare Hemipteran-Iassus scutellaris. The Psocopterans-Graphopsocus
cruciatus and Stenopsocus immaculatus were also recorded, though neither are confined to elm.
Lastly, I noted the White-letter Hairstreak Butterfly close by.
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