Fässig, Jean

Jean Fässig was a German amateur entomologist and lepidopterist active in the early twentieth century who lived in Charlottenburg, Berlin. His primary area of interest was the study of Lepidoptera, the order of insects that includes butterflies and moths. Contemporary notices published in entomological journals describe his involvement in breeding, exchanging, and selling various caterpillars and pupae from his residence on Leibnizstraße in Charlottenburg. Among the species linked to his entomological work were butterflies of the genus Satyrus and Agrotis musiva, a moth species commonly referred to as the alpine dart.

Fässig was also an active participant in the European entomological community, regularly sharing observations and research findings at scientific meetings. Records published in Entomologiske Meddelelser note his presentations on unusual geographical colour forms of Lycaena argus (the Silver-studded Blue) and Lycaena icarus (the Common Blue). Drawing on specimens collected from the island of Bornholm, he examined and compared rare regional variations in wing coloration and patterning, contributing to contemporary discussions on insect diversity and distribution. Through his breeding work, specimen exchanges, and public presentations, Fässig helped advance knowledge of European Lepidoptera among both professional and amateur naturalists of his era.