Azure Damselfly

Other common names: Azure bluet

Adult: A typical slender blue damselfly, with a rounded blue spot behind each eye and an antehumeral stripe which is noticeably narrower than the black band below it. In the male, the tip of each abdominal segment forms a black ring separating it from the next, and a black 'spike' pointing back along the segment is apparent when viewed in profile; the black is more extensive on abdominal segments 6 and 7, but the extent of black markings can be highly variable. Very similar in appearance to related species, and males are best distinguished by the characteristic dorsal black 'U' marking on abdominal segment 2 and a marking on the abdominal segment resembling paired spikes. Teneral males have a light purplish abdomen, and cream-yellow thorax markings; the upper portion of the eye is red (black in adults).

Male azure damselfly

Females typically possess a black 'hourglass' marking on the upper side of abdominal segment 2, but this is highly variable and females can most reliably be distinguished by the shape of the rear border of the pronotum, which has three shallow, backward-jutting lobes, the central one being small and rounded. Black dorsal patterning is typically more extensive, with only the borders of each segment coloured, but this too is variable. Some pale forms may have up to a fifth of each abdominal segment blue, with a 'toothed' border to the black markings. Colouration is most typically green, but can range through blue to whitish, with the thorax either green or sharing the abdominal colour.

Larva: A typical small damselfly larva, ranging in colour from brownish to various shades of green. The antennae have seven segments. Distinctive spotting behind the eyes reliably distinguishes the azure damselfly from most similar species. Two dark bands occur across the upper portion of each leg. The caudal lamellae are narrow (4x as wide as long) and rounded, ending in a gentle point. There is a shallow notch (node) midway along the upper and lower surface of each lamella, which may be indistinct - the two nodes are linked by a line which may likewise be prominent or not.

Azure damselfly female, pale form

Similar species: The azure damselfly is longer and more slender than most European species with which it might be confused. In the azure damselfly the pterostigma is monocoloured, a feature which distinguishes the species from blue-tailed damselflies (Ischnura species). There is a short black interpleural stripe, which is usually absent in American bluets (Enallagma). The female lacks a spine on the penultimate abdominal segment. Red-eyed damselflies (Eryothomma) have characteristic red eyes in the male, and blue spots behind the eyes are reduced or not present at all. Differences in markings further help to distinguish these species. In other species of Coenagrion, both sexes exhibit different markings on the second abdominal segment and (in males) the final abdominal segment. The structure of the male anal appendages (upper appendages shorter than lower, and widely separated at tip in C. puella) also differs, as does the rear border of the female pronotum. In male variable damselflies (C. pulchellum), the

antehumeral stripe is discontinuous, forming an 'exclamation mark' across the shoulder - in C. puella the stripe forms

a complete line. Of the species with which C. puella co-occurs, only the variable damselfly and Syrian bluet (C. syriacum) exhibit black 'spikes' along the central abdominal segments when seen in profile.

Azure damselfly teneral male

Caudal lamellae details

Among similarly-sized larvae, the dense spotting behind the eye is distinctive of the azure damselfly, and confusion is only likely with the similarly-marked variable damselfly. This species differs in having broader caudal lamellae (less than four times as long as wide) which are typically rounded or less strongly pointed at the tip. Most characteristically, the azure damselfly has two rows of setae in the centre of the labial mask which connect to one another at an angle of less than 90° (greater than 90° in variable damselfly), and in combination with the caudal lamellae should allow identification to species (Cham, 2009).. Additionally, most species other than C. pulchellum have either one or no bands on the femur.

HABITAT

Azure damselfly teneral male. Note the short interpleural stripe.

Most abundant in standing water with aquatic vegetation, including ponds, lakes and canals, although the species will colonise flowing water. It is less common in areas with peat or clay soils. This is a late-successional species, favouring well-established sites with dense vegetation and abundant leaf litter, and is a common resident of older garden ponds. Larvae inhabit aquatic vegetation, which they use as shelter against predation and possibly as foraging perches. The species is tolerant of a degree of eutrophication.

Reproductive habitat: Eggs are laid in aquatic plants at the water surface.

BEHAVIOUR

Breeding behaviour: Males rendezvous with females at oviposition sites; although adults appear nonterritorial, they may pursue rival males away from the rendezvous. Females oviposit while in tandem, with the male adopting a vertical 'sentinel position' while the female lays eggs to guard against predators. Tandem pairs will commonly aggregate at oviposition sites, attracted by the presence of pairs already there. This may amount to a form of herding behaviour that reduces the chance of predation on ovipositing pairs, as any predator will alarm surviving damselflies as it attacks.

Emergence: Emergence can occur at any time between the start of May until mid-September, with the highest proportion emerging during mid- and late-May and new emergences becoming scarce after the end of June. Larvae climb into emergent vegetation to complete development, making use of both emergents within the waterbody and growth at the pond margins.

Flight season: April to September throughout most of its range, reaching peak abundance between mid-May and late July. Animals may be on the wing as early as March in Algeria. In Germany, the flying season for this species begins as much as a month earlier than it did in the 1980s due to rising temperatures (Corbet & Brooks, 2008).

BIOLOGY

Breeding biology: Females lay multiple clutches of eggs, and may oviposit within a day of laying a previous clutch.

Life cycle: Larval development takes one to two years to complete. Males live for an average of 5.6 days following emergence; females 5.4 days.

TAXONOMY

Forms from northern Africa have sometimes been regarded as a distinct subspecies, C. p. kocheri, characterised by the presence of two black spots on the male's eigthth abdominal segment. However, this may simply be a gradation in patterning rather than a discrete form (Dijkstra & Lewington, 2006).

STATUS

Although the azure damselfly is widespread and presently the commonest member of its genus, its population trend is unclear and it may suffer from habitat loss in some parts of its range. Pollution and vegetation clearance represent potential threats to this species.

REFERENCES

Cham, S. 2009 Field Guide to the larvae and exuviae of British Dragonflies Volume 2: Damselflies (Zygoptera) The British Dragonfly Society: 76 pp.

Clausnitzer, V. 2007. Coenagrion puella. In: IUCN 2009. IUCN Red List of Threatened Species. Version 2009.2

Corbet, P. and Brooks, S. 2008 Dragonflies New Naturalist Series 106, Harper-Collins, London: 456pp

Dijkstra, K-D.B. and Lewington, R. 2006 Field Guide to the Dragonflies of Britain and Europe British Wildlife Publishing: 320 pp

Coenagrion puella mating pair in the 'wheel' position used for sperm transfer during copulation. Note the distinctive black 'spikes' on the blue male's abdominal segments.