The New Mexico Rare Arthropod Resource

Very little is known about the habitats and ecology of Perdita semicrocea. It has mostly been recorded in the Chihuahuan Desert, though there are several records from the Arizona/ New Mexico Plateau farther north and the lowlands of the Madrean Sky Islands to the west. This suggests it may be found in a variety of habitats including arid grasslands and shrublands. Species of Perdita are almost all oligolectic (Michener 2007). As such, their emergence is usually timed to coincide with the floral bloom period of their host plants (Wilson and Carril 2016). However, this species has been recorded on several plants in the Asteraceae family, including broom snakeweed (Gutierrezia sarothrae), southern goldenbush (Isocoma pluriflora), and goldenrod (Solidago spp.) and it has been observed from April through October, with most collections taking place in the late summer (Cockerell 1896, Ascher and Pickering 2024).

Though the nesting habits of this species are unknown, Perdita generally nest in the soil, within branching burrows that each end in a single cell, which is more or less horizontal (Michener 2007). A few species nest gregariously, with females nesting in close proximity to one another (Wilson and Carril 2016). Other species are communal nesters, with more than one female sharing a nest entrance (Michener 2007), yet others are more solitary. Instead of covering nest cells in a water proof coating, like other species in the family Andrenidae do, Perdita cover only the spherical ball of pollen provisioned for larvae in a coating (Wilson and Carril 2016). Many species are specific about the soil type they choose to nest in (Wilson and Carril 2016). Adult emergency seems to be dependent on humidity levels which indicate significant rain events above ground, at least for desert species (Wilson and Carril 2016).

Perdita semicrocea has been recorded in the southern half of New Mexico and in the southeastern most tip of Arizona, in the United States, and in the northern tip of Sonora, Mexico (Timberlake 1968, Chesshire et al. 2023). In New Mexico it is known from Cibola, Doña Ana, Otero, Hidalgo, and Socorro counties, and in Arizona, from Cochise County.

There are no conservation actions in place for this species. It is known to occur in at least one protected area, the Sevilleta National Wildlife Refuge, though it is not removed from the main threat of severe drought in this refuge. Research is needed to verify the species remains extant. In addition, a better understanding of the distribution, population size and trend, habitats and ecology, and threats is needed for this species.

The threats to this species are not well understood, though drought is likely the main threat. The southwestern U.S. saw its driest 22-year period from 2000 to 2021, since at least 800 CE (the time period used in previous climatic reconstructions) (Williams et al. 2022). Droughts are projected to become more prolonged, severe, and common in the region under future climate change scenarios (USGCRP 2018). Drought may negatively impact bee species by reducing floral resource availability (Phillips et al. 2017). In addition, declines observed in Perdita species at one site the Chihuahuan Desert have been attributed to small body size of these bees, and associated sensitivity to heat and desiccation (Kazenel et al. 2024).

The population size and trend are not known for this species. This species was reportedly quite commonly encountered on several plants in the Asteraceae family, in the late 1800s (Timberlake 1896). It is unknown if it remains common today, as it has only been recorded a few times in the last 20 years.

• Timberlake P.H.. 1962. A revisional study of the bees of the genus Perdita F. Smith, with special reference to the fauna of the Pacific Coast (Hymenoptera, Apoidea) Part V. University of California Publications in Entomology 28: (1-124).
• ITIS. 2024. Integrated Taxonomic Information System (ITIS). 2024. https://www.itis.gov/
• Ascher, J.S. and Pickering, J.. 2024. Discover Life bee species guide and world checklist (Hymenoptera): Perdita semicrocea Cockerell, 1895. 2024. https://www.discoverlife.org/mp/20q?search=Perdita+semicrocea&flags=subgenus:
• Cockerell, T.D.A.. 1896. The Bees of the Genus Perdita F. Smith. Proceedings of the Academy of Natural Sciences of Philadelphia 48: (25-107).
• Chesshire, P.R., Fischer, E.E., Dowdy, N.J., Griswold, T.L., Hughes, A.C., Orr, M.C, Ascher, J.S. Guzman, L.M, Hung, K-L.J., Cobb, N.S. and McCabe, L.M.. 2023. Completeness analysis for over 3000 United States bee species identifies persistent data gap. Ecography e06584: (13-Jan).
• Wilson, J.S. and Carril, O.M. 2016. The Bees in Your Backyard: A Guide to North America's Bees. Princeton University Press, Princeton, NJ .
• Michener, D.C.. 2007. The Bees of the World. The Johns Hopkins University Press, Baltimore : (953).
• USGCRP. 2018. Impacts, Risks, and Adaptation in the United States: Fourth National Climate Assessment, Volume II. U.S. Global Change Research Program , Washington, DC, USA : (1515).
• Williams, A.P., Cook, B.I. and Smerdon, J.E. . 2022. Rapid intensification of the emerging southwestern North American megadrought in 2020–2021. Nature Climate Change 12: (232-234).
• Phillips, B.B., Shaw, R.F., Holland, M.J., Fry, E.L., Bardgett, R.D., Bullock, J.M. and Osborne, J.L.. 2017. Drought reduces floral resources for pollinators. Global Change Biology 24: (3226-3235).