The blue-tailed damselfly, or Ischnura elegans to be scientific, is one of our commonest species and can be seen in abundance here at Langford throughout the summer months from May-September. With a UK wide distribution and a tolerance for even polluted and brackish habitats, it is one of the most likely species you will come across. It is a small species at typically just over 30mm in length.
It is worth looking closely at this species as they have an interesting range of colour forms, depending on gender and age….
Most specimens are alike in having a black upperside to the abdomen, with yellow/brown lower side, however this is where the similarities end, with the sexes and ages differing in their thorax colouration and the presence or absence of the blue coloured abdominal segment 8, which gives the species it’s name.
Mature males have the blue ‘segment 8’ and a blue thorax (form typica), however in immature males the thorax is green. This green colouration on the thorax gradually turns blue in males as they mature over the course of a few days. The situation is complicated further by the presence of teneral males – very newly emerged insects, in which the thorax and ‘segment 8’ are coloured grey/brown. This colouration is present for a short time only, before the green and subsequently blue colours develop.
Females are more complex, with multiple colour forms! As immatures they can have either a purple thorax (form violacea) or a pink thorax (form rufescens). In these forms, they are stunning creatures. And if they wasn’t complex enough, the mature forms of violacea and rufescens are different too, with individuals of violacea maturing into form infuscans, showing a brown/green thorax and those of rufescens maturing into form infuscans-obsoleta, showing a yellow-brown thorax. Neither of these mature female forms show a blue ‘segment 8’. However the story doesn’t end there, some violacea mature into form typica – resembling mature males, with a blue thorax and blue ‘segment 8’ – these individuals are known as andromorphs – females that resemble males in appearance.
Fasciniating!
Immature male showing a green thorax. (Graham Gamage).
Female of form violacea - sometimes the purple colouration is even more vivid than this (Graham Gamage).
Female of form rufescens. (Graham Gamage).