Lestes dryas (Kirby, 1890) Scarce Emerald Damselfly
There is considerable risk of confusion between this species and our other 'emerald'
damselfly - the two are similar in appearance, and have overlapping habitat
requirements. Indeed, one observer noted that L. dryas occurred together with Lestes
sponsa in seven out often sites for the former which he studied (N. W. Moore. 1980). One
superficially useful, but not really reliable, way of telling the species apart is that L. dryas
is a larger, more robust insect than L. sponsa. Where mature males can be observed, the
two species can usually be distinguished quite easily by two characteristics. The pale
powder-blue colouration on segment 2 of the abdomen covers the whole of the dorsal
surface of the segment in L. sponsa, but only some two thirds in L. dryas. The anal
appendages are also different, the inner and lower pair in L. dryas being incurved at the
tip, but more-or-less straight in L. sponsa (see Appendix C). To distinguish the females it
is necessary to view the hind end of the abdomen from the side. The projecting 'under-
carriage', the vulvar scale, is larger in L. dryas, and projects beyond the tip of the
abdomen, whereas in L. sponsa it is more or less co-terminous with the tip of the
abdomen (see Appendix C).
The earliest literature reference to L. dryas in Essex is J. F. Stephens' (1835-7) report of
it as abundant in the Thames marshes, especially in the vicinity of Plaistow. According
to H. Doubleday (1871) the species (under the name Lestes nympha) was 'rare, found on
Coopersale Common', but W. J. Lucas (1900 b) was sceptical: 'one cannot help thinking
there is some confusion amongst Doubleday's species of Lestes' (p.232). Both Lucas and
Harwood (1903) did. however, accept as valid a report of the species from Leigh, in 1891.
by C. A. Briggs and Harcourt Bath (1892) gave Wanstead as a locality. E. B. Pinniger
(1935) referred to L. dryas as still persisting in a favoured spot on the Essex marshes',
later reporting a visit to what was presumably the same locality on 12th July. 1936. when
L. dryas, 'formerly considered a great rarity' was seen in considerable numbers'. The
species was said also to occur near Southend and was seen in some numbers at
Burnham in July. Hammond's notes for 1937 state that the species was 'fairly common'
at Benfleet on July 18th. 1937. Longfield (1949 b) hoped' the species was firmly
established in Essex, though with one exception its Essex sites were beyond the L.N.H.S.
boundaries. The species was already in decline, and Longfield (1949 a) reported it as
having 'a somewhat precarious hold in a few counties of England', so that the 'few
isolated colonies should be most carefully preserved'. From 1947 A. E. Gardner
regularly visited Benfleet to study L. dryas in the field. It bred in drains choked with Sea
Club-rush, thriving in brackish water. Females were observed inserting eggs in Club-
rush stems, some six to twelve inches above the water, starting high up. and working
down. He noted that the ditches were almost devoid of water in late summer, and the
majority were completely dry in 1949. He supposed that L. dryas is able to survive in
these conditions by a delayed hatching of the eggs until after the autumnal and winter
rains (Gardner, 1952).
The known sites for L. dryas along the Thames estuary were regularly visited in the
1950s and 1960s. Benfleet being the favourite locality. It was last seen there by
Hammond in 1971 (draft letter dated 16.1.1978 in the possession of B.E.N.H.S).
Meanwhile the species was recorded elsewhere in Essex: Shenfield (1932. W. R. Fraser.
B.R.C.). South Woodham Ferrers (1950. J. H. Flint. B.R.C.). and. on the Essex/Suffolk
border, at Flatford Mill (1950. J. P. Dempster. B.R.C.).
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