Widespread and common. Flies from May to early September. It is not choosy as to habitat, though it prefers lakes and ponds, being less common on flowing water and in exposed and upland sites. It can also tolerate some salinity. Females occur in a variety of colour forms, and the distribution and relative frequency of these in Ireland is unknown. Immature females are either form violacea (violet thorax) or form rufescens (reddish-pink thorax). The immature rufescens matures into a form known as rufescens-obsoleta whilst the immature violacea can mature either into the andromorph or into infuscans.

Males of this species are similar to males of the much rarer Scarce Blue-tailed Damselfly Ischnura pumilio. However the commoner Blue-tail is a larger insect and the blue on the tail is confined to segment 8, whereas in the Scarce Blue-tail it covers the posterior portion of segment 8 and all of segment 9. The shape of the pronotum also differs, in Ischnura elegans it has a pronounced rectangular-shaped median lobe wheras in I. pumilio the median lobe is gently rounded and much less pronounced.

KEY IDENTIFICATION FEATURES

• males and most females are mainly black with blue confined to segment 8
• pterostigma is long and bicoloured