Enallagma cyathigerum (Charpentier, 1840)

Common name: Common Blue Damselfly

Preferred environment: deep open waters. Avoids shallow pools, and often favours exposed large lakes. Occurs in more exposed locations than other Irish Zygoptera.

Flight period: May to October according to locality. In Ireland, May to early September.

Adult habitat and habits: teneral individuals mature in vegetation away from breeding site. Feeding by pursuing insects in flight or by picking insects off leaves. Pairing occurs away from breeding site.

Oviposition site and behaviour: after mating pairs fly to breeding site in tandem. Oviposition occurs either in tandem with pair sitting on floating vegetation or female will lay eggs in plant stem as she descends below water often until completely submerged, Male may remain in tandem when this happens, but usually it disengages.

Larval habitat and habits: eggs do not diapause but hatch after a few weeks. The larvae are found amongst submerged vegetation often far from shore. Lifecycle is completed in one year in south but may take as long as 4 years in extreme biotopes and in northern part of range.

Emergence behaviour: emergence happens on emergent aquatic vegetation or up to several metres from shore in surrounding low vegetation.

Range: a Holarctic species. Throughout Europe apart from extreme south and Mediterranean islands, Asia to Mongolia and North America south to 40§N. Throughout Ireland to 350m.

Determination of adults: species is keyed and diagnostic characters are figured in Askew (1988). Adults of both sexes are illustrated in colour in Askew (1988) and Brooks (1997).

Determination of larvae: keys to mature larvae in Askew (1988) and Brooks (1997). Photograph of mature larva in Brooks (1997).