The eastern Bath white is very similar in appearance, ecology and
behaviour to the Bath white. Unfortunately, because of historic
conflation of the two species, its distribution is not well known. Some
books show an essentially East/West dividing line. The map above is
taken largely from Leraut (though I have excluded the northerly areas
of vagrant distribution), who for much of Europe depicts a more or less
North/South divide, with a significant overlap in Italy and the
Balkans. I know from DNA barcoding that the Swiss populations are this
species, Pontia edusa, and it
is also clear that Iberian populations are all daplidice. The relatively few that
have reached the British Isles seem to be edusa.
In Switzerland, this is one of the first non-hibernators to be seen.
Males appear in March in the valley, motoring along tracks in a manner
quite unlike that of small whites and green-veined whites, which begin
flying at about the same time. The wingbeats of eastern Bath whites are
faster and the flight generally more determined and direct. They do
occasionally stop to nectar, but rarely for long. Females have a
similar flight but do not rode in so determined a fashion, usually
flitting from flower to flower, pausing briefly on each, then zooming
off to another flower patch.
Like the other early whites, this species has several generations a year but always hibernates as a chrysalis.