The black-veined white (Aporia crataegi (Linnaeus, 1758)).
This is the most abundant and omnipresent (and, besides, most simply coloured) butterfly almost everywhere in the forest zone and woody mountains of South Siberia. Almost every year these butterflies appear in immense quantities and fly throughout June, forming incredible congregations on wet ground and swarming at flowering plants. I also often observed these butterflies flying, separately from each other, not in swarms, in the same direction for days but don't know the reason for it. Their main foodplant is the bird cherry (Padus avium), and also Spiraea media, Crataegus sanguinea and other arboreal Rosaceae, in Yakutia, Amurland and Transbaikalia also Vaccinium uliginosum. The larvae live gregareously; they hibernate on silken winter nests on the foodplant branches. Being so abundant, they often almost defoliate small bird cherry trees, the pupae densely covering thick branches at 1-3 m above the ground. There are very few fruit trees in Siberia and, besides, they are not suffer from this species, which almost does not seem to cause any substantial harm even for adult trees of its main foodplant bird cherry. But almost all local population traditionally beleive these are large whites (Pieris brassice, in Russian "kapustnitsa", i.e. "a cabbager") which eat their cabbage. In fact P. brassice penetrated into West Siberia only about 35 (first recorded by the same Y.P. Korshunov) and become abundant about 20 years ago, the cabbage suffering mostly from Pieris rapae.
Pupae on the branches of Padus avium Miller.
The bird cherry thickets on the right bank floodland of the Koen River at at the mouth of the Volchikha Rivulet, just downstream of the village Nizhnii Koen, Iskitim District, Novosibirsk Province, West Siberia, Russia. 26th May 1997. O. Kosterin.