The Blue-spot Hairstreak is a butterfly of central and southern Europe, where it frequents hot dry areas of scrubland, grassland and woodland edges and clearings. Its favoured habitats range from sea level to 2000m and include bare or lightly wooded mountainsides as well as upland plains. The white streak across forewing and hindwing plus the blue spot on the edge of the hindwing are clearly visible.
Spending much of its time at rest, often nectaring from a wide range of drought-tolerant wildflowers such as stonecrops (Sedum spp) and lavenders (Lavendula spp), this little butterfly, with a wingspan of typically 3.5cm, can be difficult to spot. Its wings, which are brown on their uppersides, are held closed except when in flight.
Satyrium spini is very common in Portugal, where the specimen shown above was photographed. It is widely recorded in Spain, southern France, Germany and Poland, and across the Mediterranean region its range extends through Greece and Turkey into the Middle East.
This butterfly has just a single brood. The larval foodplants are buckthorns (Rhamnus spp), and whitish eggs are laid in small groups on or near forks in woody twigs of these plants during the summer. The larvae develop rapidly, but then they remain inside the eggs during winter and not hatch until March, when the cold weather has passed. Green and minutely hairy, with cream markings, caterpillars of the Blue-spot Hairstreak secrete a sugary substance and are tended by ants. The caterpillars, which are green, hairy and tapering from head to tail, grow to a length of about 1.5cm..
The chrysalis, attached by a fine silken girdle to a leaf of the foodplant, is brown and speckled and covered in fine short bristles.
Blue-spot Hairstreak butterflies emerge from their chrysalises in mid to late May through to the end of July; the greater the altitude and/or longitude the later the peak emergence.