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Libellula depressa Linnaeus Broad-bodied chaser
Description The very broad, flattened and pale blue abdomen of mature male L. depressa,
and the large black-brown patch at the base of each wing distinguish this
species from the three other male libellulids that possess a blue abdomen. In
immature males and in females, the abdomen is yellowish brown with yellow
markings laterally which are most prominent on segments 4-7. In males, a
blue pruinescence develops with age and covers the abdomen, except for
segments 1, 2 and 10 which remain dark, and the lateral yellow markings
which may be slightly reduced in size. The pattern of markings on the wings is
the same in both sexes although, in the female, the dark basal patches are
more heavily marked with yellow veins than in males. These wing markings
and the very broad short abdomen distinguish females from those of other
libellulids. The thorax is dark brown in both sexes, with two pale whitish
stripes dorsally. The eyes are dark brown.
Habitat L. depressa breeds in well-vegetated ponds, lakes, canals and ditches.
However, it is also one of the first dragonflies to colonise a newly created water
body and will breed in small garden ponds, and in farm ponds that are mildly
polluted. In south-west Britain, it occasionally breeds in peaty bog pools.
Breeding biology The male is territorial and very aggressive. The population density of males
rarely exceeds 8 per 100 m of water's edge. Therefore, small ponds will
seldom if ever hold more than one male. As with other large libellulids, males
perch on stems of tall emergent plants or on exposed sticks and make
frequent flights to chase off intruding males, returning to the same perch.
Copulation occurs in flight and only takes a few seconds. During oviposition,
the female flies very low in and out of the vegetation at the water margin and
thrusts her eggs into the water by flicking her abdomen downwards. Males
sometimes guard females during this process, but females frequently oviposit
alone and when no male is present at a pond. The eggs hatch after two to
three weeks and the larvae, which live amongst the plant debris or silt at the
bottom of the pond, probably take two or three years to develop in most
circumstances, but can complete their life cycle in one year (Holmes &
Randolph 1994). Emergence is usually synchronous, and takes place on
marginal and emergent vegetation.
Flight periods L. depressa is on the wing from mid-May to early August. On larger ponds and
Status and distribution
European and world
distribution
lakes it may be seen with species such as Anax imperator, Aeshna grandis,
Orthetrurn cancellatum and the common damselllies.
L. depressa is found widely in southern Britain, thinning out in the north
midlands. It has conspicuously declined in eastern England from the Fens to
Yorkshire, having been lost from many former sites owing to agricultural
pressures, especially the loss of farm ponds. However, there are some signs of
a recovery in recent years. There is a single record from Ireland. Miss Ball, a
celebrated entomologist, recorded it from Glendine, Co Waterford, in July
1834. It is unlikely that a mistake could have been made in the identification of
this distinctive species as the specimen was identified by Sélys-Longchamps
(1846). An Irish specimen, possibly that of Miss Ball, is in Trinity College
Museum, Dublin (King & Halbert 1910).
L. depressa occurs throughout Europe as far north as southern Scandinavia,
and east to the Middle East and western Asia. It is absent from North Africa.
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