Male, Italy, painted from photographs of a set specimen in Bozano's
Guide to the Butterflies of the
Palearctic
Region (with reference to live specimens from
Roger
Gibbons's website)
Distribution
This species does not fly
in
Switzerland and I have yet to see it. It is a butterfly of dry, grassy,
flowery meadows and open woodlands where its foodplant, meadowsweet
grows.
It is
very similar in size and general appearance to the lesser marbled
fritillary but in both sexes and on both wings the spots in the outer
post-discal row are rounder and less obviously part of the submarginal
pattern - hence the English name, 'twin spot' fritillary. This
distinction can be relatively subtle on the upperside but is very clear
on the hindwing underside. This also lacks the violet hues of the other
two Brenthis
species, the twin rows of spots being set clearly in a yellow and
orange ground.
The species flies in Italy, France and Spain, where it is generally
local and
uncommon, and in south-eastern Europe, where it is said to be commoner.
It is on the wing from May, or April in the Balkans, to July or early
August. The caterpillar hibernates while still in the egg, hatching out
and beginning to feed in February or March.