Pyrgus cacaliae (Rambur, 1839)

Host plants:
Potentilla aurea, Potentilla crantzii and other alpine Potentilla species. Probably also other herbaceous Rosaceae are possible (e.g. Sibbaldia procumbens), though not yet clearly observed in the field.

Habitat:
Pyrgus cacaliae occurs on high alpine slopes and in stream valleys from about 1700m above sea level upwards. Pyrgus cacaliae is particularly common in the Central Alps, and here, for example, in the Silvretta area at 2000-2500m above sea level. The larval habitats are often more sparsely vegetated, south-facing places in mountain pastures.

Life cycle:
Pyrgus cacaliae hibernates twice, at the first time in the first or second larval instar (e.g. observations of caterpillars in mid-October 2005 in the west Austrian Rätikon at 2100m above sea level), probably very rarely also in the third instar (after early flight time in the given year), then the second time as a pupa. In the first winter the larva constructs a dense, fine white housing preferably slightly higher among the youngest, surviving leaves of the plant. Some caterpillars overwinter also a second time as L3 or L4 as observed in the Silvretta area in 2004, so that larval development very occasionally can last three winters. The flight time is very dependent on mountain spring, ranging from the end of May (in extreme cases, already mid-May) to August.

Locally the two year life cycle can result in adults flying only every second year (e.g. Austrian Rätikon: odd years) or at least in different abundances.

Endangerment factors:
Currently Pyrgus cacaliae is still not endangered severely in the Alps. Locally populations can be under threat because of tourism (skiing!) or energy management (hydroelectricity).

Remarks:
The males congregate, like the other species (Pyrgus andromedae, P. alveus), along mountain streams or higher forb communities, where territories are occupied, which serves the meeting of females in the vast mountain areas.

Pyrgus cacaliae is widespread in the Alps and locally common there (e.g. Central Alps). In addition, it occurs rarely in the Pyrenees and some mountains in South Eastern Europe (Bulgaria, Romania). But it is very local in the German Alps, where only a very few sites are known (e.g. in the southern Allgäu Alps) and there locally threatened by excessive tourism and the corresponding infrastructure.

Hints on determination:
Pyrgus cacaliae can be confused with Pyrgus serratulae which occurs syntopically and also simultaneously. Hints for correct determination can be found especially on hind wing undersite. In Pyrgus cacaliae the rounded white spot at the upper margin is often (but not always) not regular oval what stands in contrast to the generally typical oval spot in P. serratulae. Additionally the underside of P. cacaliae is much more indistinct and faded. The exclamation mark at the lower margin of hind wing underside is located half on dark and half on light background, but is often not well developed. Confusion with Pyrgus andromedae is less likely (see there).