north-west, but it is seemingly absent, or scarce, on the east coast of the county. Aeshna
grandis breeds in a very wide variety of still and moving-water sites, having been
observed ovipositing in the Cam. in the extreme north-west, the Chelmer/Blackwater,
numerous flooded pits, and smaller ponds. It seems to be tolerant of pollution, and is
found in some sites where only it and Ischnura elegans seem capable of surviving. It has
not. however, been so far observed breeding in the brackish coastal dykes. Flooded pits
of various sizes and ages are probably the most important type of breeding site for A.
grandis in Essex.
Aeshna mixta (Latreille, 1805) Migrant Hawker
Formerly known as the 'scarce' hawker, this name is no longer appropriate. There are
three other hawker species with which A. mixta might be confused. Brachytron pratense
looks similar in the field, but its flight period is early, and does not overlap with that of A.
mixta, which is not on the wing in Essex before the beginning of August. Aeshna cyanea
has the paired blue (or green) marks on the abdominal segments fused into bands on
segment 9 and 10, whereas in A. mixta they remain separate even on these hindmost
segments. In addition. A. mixta does not have the bright green thoracic 'eye' markings
which are so prominent in A. cyanea. The serious problem for field-observation is to
distinguish A. mixta and Aeshna juncea. In the males (paired markings on the abdomen
blue) there are clear, strongly marked thoracic stripes in A. juncea, but only rather faint
or non-existent thoracic markings in A. mixta. In the females (paired markings on the
abdomen green) thoracic stripes are more or less absent in both species. A useful field-
character which applies to fully mature adults of both sexes, is the bright yellow leading
edge of the wings in A. juncea (in A. mixta this is dull brown in both sexes). Less reliable,
but usually quite noticeable, is the fact that A. juncea is a significantly larger and more
gaudily coloured insect than A. mixta. Where close examination of captive specimens,
or good quality photographs is possible, then other differences in markings and wing-
venation can be used (see Appendix C).
Aeshna mixta was primarily a mediterranean species which has recently been
extending its range northwards. It is now very widespread and abundant in Essex,
though it remains unclear how large a proportion of sightings are of immigrants, as
against locally breeding populations. That it is a widespread breeding species in Essex
is. however, no longer in doubt. Nymphs have been collected from coastal borrow dykes
(P. Wilson. pers, comm.) and I have observed females ovipositing among Sea Club-rush
in this habitat. The species also breeds in flooded sand and gravel pits, pairing having
been observed around and among emergent vegetation (Reed-mace) at the edges of
these sites. There are also reports of breeding from lakes and ponds in urban parks (e.g.
Victoria Park. Laindon, 1983. D. S. Walker; and Heronry Fond. Wanstead Park. 1981, C.
W. Plant), from a winter-wet marshy hollow (Laindon, 1983, D. S. Walker) and from the
Cornmill stream ('several hundred exuviae'. 1983. B. Eversham). The species also
established itself as a breeding species within three years or so of the formation of an
artificial lake in the High Woods area north of Colchester. Very swift and acrobatic
'courtship' was observed to take place here (D. S. Walker also observed this at a south-
west Essex site: 'aggressive pairing, loud clashing of wings, tumbling flight'), with
ovipositing apparently taking place both by females 'solo' among stems of Reed-mace
and in tandem more randomly over open water.
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