In Essex perhaps the most favoured breeding sites for this species are flooded sand
and gravel workings. Orthetrum cancellatum is one of the first colonisers of these, and
does not require extensive marginal vegetation. The species also breeds in coastal and
estuarine borrow dykes, often where these contain brackish water. Again, O. cancellatum
is one of the early colonisers following dredging and mechanical excavation of these
dykes, but it continues to breed in them and associated brackish pools well after the
typical marginal vegetation of beds of Sea Club-rush have become established.
Orthetrum cancellatum also breeds in ornamental ponds and lakes, especially in their
early stages, or when there is substantial erosion of the banks (e.g. where a lake is
intensively fished or visited by the public, as at Hatfield Forest). Finally, there are some
breeding records from moving-water sites. Territorial males were observed on the
Chelmer/Blackwater Navigation in 1984. and G. White (pers. comm.) has observed
breeding on the Old River Lee, the Horsemill Stream and the Cornmill Stream
(exuviae) in the far west of the county.
As indicated above, the males are territorial, and spend a good deal of their time
hawking a beat along the margin of the breeding site. In this respect they resemble
hawkers in behaviour, and are, indeed, victims of aggression from large hawkers
(notably Anax imperator) on adjacent territories. Possibly as an adaptation to this rather
unequal competition, they tend to fly very close to the surface of the water, and to the
marginal vegetation (compared with hawkers which tend to fly higher and/or further
out).
Males of O. cancellatum also, however, have a more typical darter-like behaviour,
which consists in settling for some time on a protruding rush or reed-stem at the water
margin, wings down-swept, making rapid sorties and returning to the perch. It may be
that these are distinct feeding and mate-locating tactics, and it would be interesting to
see how much time is spent by males in each 'mode'. Females appear to spend more of
their time away from water, returning there to breed. Copulation typically takes place in
flight, though sometimes the pair appear to hover in the air alongside marginal
vegetation so that it may be they gain some support from this while continuing to beat
their wings. I have also seen mating pairs (usually late in the day) at rest on bare mud or
gravel and on these occasions copulation is much longer in duration. Single males are
also very frequently observed sunning themselves on these bare patches, and it appears
that such basking sites may well be a habitat requirement which explains their ready
colonisation of newly created sites.
Egg-laying usually takes place immediately after mating, the female repeatedly
dipping her abdomen into the water near the margin of the pond or dyke, and moving
progressively along the length of the male's territory. Always, in my experience, egg-
laying females are accompanied by their mates, which fly around them, two to three feet
away, until the process is completed. The flight period is from the beginning of June to
the last week in August, peaking in July.
Aside from the temporary acquisition of Coenagrion scitulum, this species is the only
one to have become established as a breeding species in Essex since W. H. Harwood's
(1903) list. In fact, it was not recorded in Essex until it was discovered at Hainault Forest
by E. B. Pinniger on 4th August, 1934 (Pinniger, 1935). Pinniger in fact established that
the species was breeding there by collecting a nymph from the site (1936). Hammond's
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