Blue-tailed Damselfly Colour Forms

The Blue-tailed Damselfly/Common Bluetail (Ischnura elegans) boasts a glittering array of different colour form females. The normally documented forms number 5, 2 of which are immature colour variations and 3 of which are mature forms. To trap the unwary, one of the mature forms is androchrome, resembling the mature male. Understandably, whilst this variety adds to the interest, it can also cause a little confusion.

Not only do we have one female form resembling the mature male, the confusion is further compounded by the immature male being a 6th colour form with a turquoise thorax. That’s what most (all?) the books say. What I have not seen the books mention is that not all those with a turquoise thorax are male, some are female. So, there actually appear to be at least 6 female colour forms though a friend and fellow odo-nutter, Steve Cham, has mentioned yet another brown variant.

The confusion is not aided by there being a couple of different naming conventions in use for the female colour forms. There are older “traditional” names (violacea, rufescens, typica, infuscans and rufescens-obsoleta) and newer, “simpler” names (A-, B- and C-type, mature and immature) proposed by K-D Dijkstra in his excellent book.

Below is my diagramatic attempt at clarification. I must point out that my placing of the female turquoise coloration is something of an assumption. Since the turquoise male changes into the familiar mature blue colour, it seems reasonable to assume that the turquoise female might also change into the blue form, i.e. typica. As typica females begin life as the violacea form, it also seems fair to assume that the turquoise might be an intermediate form in between violacea and typica.

I am indebted to Roger Hale for his photograph of the female turquoise form (below centre).


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