Unveiling the Trichoptera (Insecta) of Parque Nacional da Serra do Divisor: the first caddisfly checklist from Acre, northern Brazil

The biodiversity of Amazonian entomofauna still has several gaps to be filled, particularly in remote regions where logistical constraints hinder systematic surveys. To reduce the “Linnean shortfall” in the western Brazilian Amazon, we conducted the first comprehensive survey of Trichoptera in Parque Nacional da Serra do Divisor (PNSD), the largest protected area in the state of Acre, Brazil. Sampling was carried out in 2022 and 2023 at 22 sites, including the Moa River and its tributaries, using Malaise traps, collapsible Pennsylvania traps, and luminous sheets. A total of 2,233 specimens were collected, representing 13 families and 31 genera. Eight families and 23 genera are reported here for the first time in the state of Acre. A total of 26 species were identified, including 19 new state records and three new records for Brazil: Helicopsyche (Feropsyche) selanderi Ross 1956 (Helicopsychidae), Phylloicus bicarinatus Prather 2003, and Phylloicus kinovos Oláh 2016 (Calamoceratidae). Furthermore, 44 putative species new to science were discovered, predominantly within the Glossosomatidae, Hydropsychidae, and Leptoceridae. These findings represent a 118,8% increase in the known Trichoptera diversity in Acre and highlight the PNSD as a key hotspot for endemic aquatic insects. Our results emphasize the urgent need for continued taxonomic research and for maintaining protected areas to safeguard the unique biodiversity of Amazonian montane systems.