While in Europe, Avinoff spent his spare time traveling throughout the mountainous areas in Europe and Asia collecting butterflies. Avinoff would trace their genetic evolution through different valleys, since the mountains separating those valleys prevented different butterflies from mating. He found the Himalayas to be the ultimate proving ground. Avinoff's collection of Rhopalocera from the Pamir Mountains and Central Asia currently resides in the Zoological Museum in St. Petersburg. This collection of some eighty thousand specimens was appropriated by the Soviet government. Following World War II, the Mellon family asked to retrieve the collection, but this was refused.