Drosophilidae collection records from the “Waterfall fig” site, Thailand

Drosophilid flies can be sampled from various resources using a range of methods—here we provide an exhaustive list of all drosophilids sampled from a naturally fermenting fruit resource using a sweep net in a rainforest in the Khao Sok region of Thailand. The resource is a thick mat of new and old fermented figs that have fallen naturally to the rainforest floor beneath a large cauliflorous Ficus sp tree (images provided in Polak & McEvey, 2026) over many weeks. Such a resource is of long duration and has been part of the flies’ preferred habitat throughout their evolution. Our objective was to sample directly from a natural resource not an artificial, short-duration, fruit bait like fermented bananas in a bucket trap stationed randomly in rainforest habitat overnight. Species of the Drosophila immigrans species group have been the target of this survey. We have identified 10 distinct species with seriate spinescent femoral setation, typical of the immigrans sp gp. Drosophila hypocausta, while present at other sites in the area, was not encountered at this site. Drosophila sulfurigaster, D. albomicans, and D. siamana were common; D. burmae and D. formosana (see McEvey & Polak, 2024a–e) were present in low frequency. Five additional immigrans sp gp species were found at relatively low frequency but require further taxonomic study; one Drosophila s.str. species outside the immigrans sp gp is present but rare. In the list we have made no attempt to identify all the species of the Drosophila subgenus Sophophora, 29 species are known from Thailand (Bächli 2026), at least 10 species were present in this sample.