This butterfly gets its common name from the long thin tail on the trailing edge of each hindwing. The tails are black with white tips, but unfortunately the butterfly pictured above has suffered damage to its hindwings and so the tails are not evident.
The Long-tailed Blue is a very rare sight in Britain, where the winters are generally too cold for its survival. The pale bar on the intricately patterned underwing helps distinguish it from the very similar Lang's Short-tailed Blue, Leptotes pirithous.
The specimens shown here were photographed in the Algarve region of Portugal. (Pictures: Rob Petley-Jones)
In Britain the Long-tailed Blue occurs along the south coast of England and the Channel Islands very occasionally as a migrant. On mainland Europe this is a butterfly of southern countries
The larval foodplants used by the Long-tailed Blue include various peas (Fabaceae), and it is considered a pest of Broad Bean and Pea crops in agricultural areas where it feeds first on the leaves and then on the contents of the seedpods.
In the Allgarve and in southern Spain these butterflies can be seen throughout most of the year; the specimens shown here were seen in May.