At bugle, its favourite plant. Switzerland, May 2009.
This is the most widespread and familiar of the Boloria
species. It flies from late April or early May in most of Europe (from
late May in the north and at altitude), typically in a single brood but
with a weaker second brood in hotter areas. Although a woodland
species, most often seen flying along spring rides and nectaring on
bugle and other flowers, it reaches up into the mountains and can be
found on flowery alpine slopes well away from the nearest trees.
Males are a rather bright orange above, with characteristic 'floating
triangles' around the borders, rather than closed arches. Altogether,
this gives them an open, spotty appearance, unlike the linear
appearance of small pearl-bordered fritillaries. In females - which are
generally larger and less bright - the triangles (or chevrons) often
touch the border, enclosing discrete spots, more like small
pearl-bordered. Another useful feature from above is the distribution
of spots in s.2 of the forewing. In pearl-bordered, the inner mark,
near the cell, is relatively large, and the post-discal spot never
seems terribly far away from it, dividing the space to the submarginal
triangle in a ratio between 1 : 1 and 2 : 1. In small pearl-bordered,
the post-discal spot looks further away, dividing this space in a ratio
of (typically) more than 2 : 1. Beneath, the two species are readily
separated. The pearl borders of the pearl-bordered fritillary are edged
internally by red chevrons, with reddish post-discal spots inside that.
In small pearl-bordered fritillary the pearly are edged in black, with
black post-discal spots.
The caterpillars feed on violets of various species, including the
familiar dog violets and early dog violets, as well as sweet violets.
Although in hot parts of Europe some may complete their development the
same year, flying in August and September, most go into hibernation
relatively soon and feed up the following spring.