An updated checklist of Butterflies (Insecta: Lepidoptera) of Sikkim with some new distribution to the state

The butterfly fauna of Sikkim comprises 805 species belonging to six families. In the present checklist, we document 536 species, Nymphalidae representing the highest diversity with 214 species and Riodinidae the lowest with 10 species. Based on literature survey; an additional 269 species of butterflies were compiled, where Lycaenidae was the most diverse family (90 species) and Riodinidae the least represented (one species). Species recorded both in earlier studies and in the present survey were included in the updated checklist. Several species previously reported in Sikkim were not encountered during our fieldwork, possibly due to local extinction driven by habitat alteration or climatic factors, or due to the need for wider and more intensive surveys in the future. Conversely, multiple species- Ypthima fusca , Rohana tonkiniana ; Arhopala ganesa , Erionota apex are recorded here for the first time from the state. Our survey also documented rare, uncommon, exclusive and endemic species, including Teinopalpus imperialis , Parnassius hardwickii (Papilionidae); Dercas verhuelli , Delias sanaca (Pieridae); Charaxes delphis, Bassarona durga (Nymphalidae); Euaspa pavo (Lycaenidae) and Zographetus dzonguensis (Hesperiidae) etc. Of the species recorded, 153 butterfly species are protected under the Indian Wildlife (Protection) Amendment Act, 2022, most of them under Schedule II (127 species). According to the IUCN Red Data Book, 27 species are classified as Least Concern, one species Near Threatened, while 508 species remain Not-Assessed. The presence of over half of India’s butterfly species within Sikkim highlights the region's exceptional ecological significance. Despite this richness, large areas of the state remain poorly explored, and the distribution patterns of many species are still unknown, emphasizing the need for more extensive and systematic surveys in the near future.