Rhopalolemma robertsi

Roberts' Rhopalolemma Bee

Family: Apidae · Class: Insecta · Order: Hymenoptera

Conservation status: G1 S1

Roberts' Rhopalolemma Bee is a small, rare cuckoo bee in the family Apidae, subfamily Nomadinae, tribe Biastini. This species belongs to a genus containing only two known species, both restricted to desert environments of the southwestern United States. Physical characteristics of this species have not been extensively documented in the scientific literature, though it is known to be a cuckoo bee that parasitizes the nests of other bee species. Rhopalolemma robertsi has an extremely limited known range, occurring only in southeastern California and Arizona. The species was first described by Roig-Alsina in 1991 based on a single female specimen collected on May 3, 1973, from 8 kilometers south of Twentynine Palms in San Bernardino County, California (BugGuide). This location in the southern Mojave Desert had been well-collected by entomologists for many decades prior to the discovery of this species, highlighting its rarity and elusiveness. Additional specimens have since been discovered in southern Arizona. The species inhabits desert environments, specifically areas within the Mojave Desert ecosystem of southeastern California and adjacent desert regions of Arizona (BugGuide). The original collection site near Twentynine Palms represents typical Mojave Desert habitat, characterized by sparse vegetation adapted to extreme aridity and temperature fluctuations. The species appears to be associated with areas that support populations of its presumed host bee species, though specific microhabitat requirements remain poorly documented. As a member of the cuckoo bee subfamily Nomadinae, Rhopalolemma robertsi exhibits brood parasitic behavior, laying eggs in the nests of other bee species. The female cuckoo bee infiltrates host nests and deposits her eggs, with the developing larvae consuming the host's provisions intended for their own offspring. However, specific host relationships, seasonal activity patterns, and detailed reproductive biology for this species have not been well documented in the scientific literature. The timing of adult activity is partially known from the May collection date of the type specimen, suggesting spring emergence, but the full phenology remains unclear. Rhopalolemma robertsi carries a conservation ranking of G1 S1, indicating it is critically imperiled both globally and within California. This ranking reflects the species' extremely limited known distribution, small population size, and rarity in collections despite decades of sampling effort in its known range. The species faces potential threats common to desert-dwelling insects, including habitat loss from urban development, off-road vehicle use, and climate change impacts on desert ecosystems. However, no formal conservation assessments or recovery plans have been developed for this species. The extreme rarity of Roberts' Rhopalolemma Bee in scientific collections, combined with its restricted desert habitat, makes it a species of significant conservation concern. Further research is needed to better understand its distribution, host relationships, and ecological requirements to inform appropriate conservation strategies for this critically imperiled desert endemic. This species is included on the California Department of Fish and Wildlife's Special Animals List.

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