Lang`s Short-tailed Blue (Leptotes pirithous) is a small butterfly with a wingspan of 21–29 mm in males and 24–30 mm in females.
The uppersides of the wings are purple bluish in males and bluish-brown in females.
The Lang`s Short-tailed Blue can be easily confused with the Long-tailed Blue (Lampides boeticus) which also occurs in southern Europe.
However, the Long-tailed Blue is slightly larger and has a distinctive continuous white band on the underside of the hindwing which is missing in Lang`s Short-tailed Blue.

Collesalvetti, Livorno, Tuscany, Italy, 22 September 2019