THE BUTTERFLIES AND LARGER MOTHS OF SELECTED
ESSEX HABITATS
SAWBRIDGEWORTH MARSH NATURE RESERVE
by J. L. Fielding
Sawbridgeworth Marsh Nature Reserve consists of about nine acres of old willow plantation and
fourteen acres of marsh and grassland. It straddles the county boundary, the greater part lying in
Hertfordshire which crosses to the Essex side of the River Stort to take in Hyde Hall, its grounds and
some adjacent farmland. The marsh is bounded on the western side by a backwater of the river and on
the eastern side by the Sawbridgeworth to Gaston Green road. Until 1969 the whole of the Reserve
was part of the Hyde Hall estate and the grassland and marsh were formerly used as rough pasture for
the summer grazing of cattle.
The 1838 tithe map shows five named pastures, two of which, Round Moors and Rush Mead,
indicate that it has long been a wet place. The many drains which must have kept the marsh in
reasonable condition for grazing are now well silted up and where they were cut through the sloping
ground below the road there is as much as five feet of waterlogged peaty soil.
The nine acres south of the main drain, which has to be kept open to avoid flooding the road, was
planted with cricket-bat and crack willows in the 1920s and is frequently flooded during the winter
months. It is still being maintained as a willow plantation. The whole area north of the main drain was
used for summer grazing until the early 1960s when it became derelict except for about two acres on
the higher ground next to the road which was subsequently fenced off and used for grazing for horses.
A further one acre was enclosed for horse grazing in 1981.
Sawbridgeworth Marsh was purchased jointly by the Essex Naturalists' Trust and the
Hertfordshire and Middlesex Trust for Nature Conservation in 1969 and since then it has been
managed as a nature reserve to maintain and if possible improve the richness and diversity of the plant
and animal life which it contains.
The marsh is fed by springs and flushes rising on the valley slope, and it is partly a sedge bed with
large areas dominated by great hairy willow-herb, common reed and reed-grasses. Reedmace is
spreading rapidly in some of the wetter parts. The valley slope and the silted-up drainage ditches
support the greatest diversity of plant species and contain a number of local rarities as well as a fine
display of southern marsh orchids each June. To maintain this diversity, it is necessary to mow the
whole of the species-rich area in autumn or winter and remove or burn the enormous amount of cut
material.
During recent years, 169 species of macrolepidoptera have been recorded on the marsh as well as a
number of micros including Ochsenheimeria urella (bisontella), Elachista alpinella, Parapoynx
stratiotata and the rare Nascia cilialis, a new record for Hertfordshire found by RW.J. Uffen on
8 July 1976. Trapping has been done only between April and September, so this total does not include
any autumn or winter species. Eighteen species of butterfly are included, but no rarities. Peacocks and
small tortoiseshells are usually abundant, particularly in late summer when they may often be seen in
large numbers feeding on the flowers of water-mint and hemp agrimony.
Apart from the common moths and those well distributed in the surrounding district,
Sawbridgeworth Marsh has its specialities. The blackneck (Lygephila pastinum) is common because
of the abundance of tufted vetch, its foodplant, and more than 12 came into a light-trap during a two-
hour period on 19 July 1981. The rarer moths have included the slender pug (Eupithecia tenuiata),
valerian pug (E. valerianata), round-winged muslin (Thaumatha senex), small wainscot (Photedes
pygmina), bulrush wainscot (Nonagria typhae), brown-veined wainscot (Achanara dissoluta) and
fen wainscot (Arenostola phragmitidis), all marshland feeders. Other species of note are the emperor
moth (Saturnia pavonia), the white-spotted pinion (Lomographa bimaculata) and the double-lobed
(Apamea ophiogramma) which feeds on the reed-grass (Phalaris arundinacea) and four of which
came to light on 19 July 1981. The large caterpillars of the drinker moth (Philudoria potatoria) are
frequently seen in their season feeding on the coarse marshland grasses, and the moth can be
particularly common, more than 30 having come to light on 19 July 1981.
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