Ochthebius crassalus

Wing Shoulder Minute Moss Beetle

Family: Hydraenidae · Class: Insecta · Order: Coleoptera

Conservation status: G1G3 S1S3

The Wing Shoulder Minute Moss Beetle (Ochthebius crassalus) is a small aquatic beetle in the family Hydraenidae, subfamily Ochthebiinae. As indicated by its common name, this species belongs to the minute moss beetles, a group characterized by their diminutive size and association with moss-covered aquatic habitats. The beetle's scientific classification places it in the subgenus Ochthebius (Ochthebius), within the tribe Ochthebiini and subtribe Ochthebiina. This species is endemic to California, representing one of the state's specialized aquatic invertebrates. The Wing Shoulder Minute Moss Beetle occurs in limited locations within California, though specific distributional details remain poorly documented in the scientific literature. According to the U.S. Fish and Wildlife Service, the species is known to occur only in California, suggesting a highly restricted range typical of many endemic California beetles. The Wing Shoulder Minute Moss Beetle inhabits aquatic environments where moss growth provides both shelter and feeding opportunities. Like other members of the genus Ochthebius, this species likely occupies the margins of streams, seeps, or other freshwater habitats where moss and algae accumulate. These beetles typically require clean, well-oxygenated water and are often found in areas with consistent moisture levels. The specific microhabitat requirements and substrate preferences for O. crassalus have not been thoroughly studied, limiting our understanding of its precise ecological needs. Detailed behavioral and ecological information for the Wing Shoulder Minute Moss Beetle remains limited. Members of the genus Ochthebius are generally detritivores and algae feeders, using specialized mouthparts to scrape organic matter from surfaces. They likely feed on moss, algae, and organic detritus found in their aquatic habitats. Reproductive biology, seasonal activity patterns, and life cycle duration for this species have not been documented in available literature. The beetles are presumably active year-round in California's mild climate, though seasonal abundance patterns are unknown. The Wing Shoulder Minute Moss Beetle carries a global conservation rank of G1G3, indicating it is critically imperiled to vulnerable globally, and a state rank of S1S3, suggesting similar conservation concern within California. These rankings reflect the species' apparent rarity and restricted distribution. The beetle is tracked in the U.S. Fish and Wildlife Service's Environmental Conservation Online System as a species of conservation interest, though it does not currently appear on federal endangered species lists as of December 2025. Primary threats to this species likely include habitat degradation, water diversions, pollution, and climate change impacts on California's aquatic ecosystems. The beetle's apparent dependence on specific moss-covered aquatic habitats makes it particularly vulnerable to environmental changes that alter water quality or flow patterns. Limited scientific knowledge about this species hampers conservation planning efforts, highlighting the need for additional research on its distribution, habitat requirements, and population status.

Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, and more.