The New Mexico Rare Arthropod Resource

Stanford's Blue is limited to Pinyon-Juniper woodlands which support the species obligate larval host Cushion Buckwheat (Eriogonum ovalifolum)  (Fisher 2009, Cary and Toliver 2024, iNaturalist 2024, NatureServe 2024). The species seems to be univoltine with flight records across its range stretching from late April into late May (Cary and Toliver 2024, iNaturalist 2024). During flight adults feed on the nectar of their sole larval host plant, Cushion Buckwheat, and never stray far from stands of their host (Cary and Toliver 2024, NatureServe 2024). Stanford's Blue overwinters as a pupae which emerge the following spring although it is hypothesized that they may be able to extend pupal diapause for several years (Cary and Toliver 2024).

This rare species occurs in small populations within a limited range that stretches from southeastern Utah and southwestern Colorado to extreme northwestern New Mexico (Cary and Toliver 2024, GBIF.org 2024, iNaturalist 2024). Observations of this species fall between 1,645 and 1,829 meters in elevation (Cary and Toliver 2024).

There are currently no known conservation actions being taken to protect this species and it does not have any status throughout its range. However, the species did undergo a state assessment in Colorado and was found to be Imperiled there (iNaturalist 2024, NatureServe 2024). Currently more research is needed on the population size, trend, and extent of this species. We also lack critical information on this species life history and the threats to it which are necessary for its conservation.

Threats to this species are not well understood, though the sole host plant, Cushion Buckwheat, is threatened by drought, invasive species, fire, development and off-road vehicles (USFWS 2009). This has resulted in at least one variant of Cushion Buckwheat becoming listed as federally endangered (USFWS 2009). In the listing decision, the US Fish and Wildlife Service suggested that Cheatgrass (Bromus tectorum) and the increased potential for wildfire that its presence causes, is a major threat to the species (USFWS 2009, 2022; Fusco et al. 2019). They also found climate change and drought to be major threats, which could reduce germination rates, growth, and reproduction (USFWS 2022). Host plant specialization, as is seen here, is known to increase the risk of extinction for butterflies (Ehrlich and Murphy 1987, Kotiaho et al. 2005, Palash et al. 2022).

The population size and trend are not known for this species. Determination of population size and monitoring of population trends is necessary to ensure the population is stable. Especially as several widespread, relatively common species of butterfly are in decline across the American west (Forister et al. 2021).

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