Overview
The Nokomis fritillary is a large, striking butterfly that most people in western Colorado have never noticed, for reasons that have everything to do with where it lives. It inhabits seeps and springs — the permanently wet, often hidden places where groundwater emerges from hillsides and sustains wet meadows and lush herbaceous vegetation in an otherwise arid landscape. These are not the obvious, accessible habitats where casual observers look for insects. They are out-of-the-way places that require deliberate searching and a specific knowledge that something rare lives there.
Fewer than 20 known sites exist across the entire United States range. Colorado’s western slope — particularly in Mesa, Garfield, and Delta counties — holds some of the most important remaining populations. USFWS listed the Nokomis fritillary as federally threatened in 2024, a recent listing that reflects the species’ extremely limited and fragmented distribution and the ongoing threats to the seep and spring habitats it requires.
The butterfly is entirely dependent on seep and spring complexes where native violet species grow in the permanently moist substrate. Water diversion and groundwater pumping that dries seeps and springs is the most acute threat, because the loss of a single seep complex can eliminate an entire population — and with populations this few, the loss of a single site matters.
Natural History
The Nokomis fritillary (Speyeria nokomis nokomis) is a large fritillary — wingspan 2.5 to 3.5 inches. The upper wing surfaces are orange and black in the typical fritillary pattern; the hindwing underside displays the silver spots that give the fritillary group their name, here particularly bright and clearly defined. Males are noticeably brighter orange than females.
Adults fly from late July through September, with peak emergence in August. The flight window is narrow — roughly six to eight weeks — and adults are highly localized, rarely straying far from the seep and spring complexes where they emerged. This site fidelity concentrates both the breeding population and the vulnerability: a population that remains tied to a specific seep complex cannot colonize nearby habitat if its home site is disrupted.
Larvae feed exclusively on native violet species (Viola spp.) growing in the moist soils of seep and spring margins. The same dependence on native violets that characterizes other fritillary species applies here, with the additional constraint that the violets must be growing in the saturated substrate of seep complexes rather than the drier soils where violets also occur. This double specialization — seep-obligate violets as larval host, seep-derived moist microclimate for larval survival — means the species has almost no habitat flexibility.
Habitat in Colorado
Western Colorado’s seep and spring complexes are the conservation focus for this species in the state. The geology and hydrology of Mesa, Garfield, and Delta counties supports the kind of perennial groundwater emergence that creates the permanently moist meadow conditions the Nokomis fritillary requires. These areas are often associated with valley margins, cliff faces, and hillsides where water-bearing geological formations intersect the surface.
The specific combination required: a seep or spring with sustained year-round groundwater emergence, a carpet of native violet species in the saturated soil nearby, and sufficient native flower diversity (particularly thistles, which are a favored adult nectar source) in the adjacent upland for adult feeding.
In the arid western Colorado landscape, these conditions are localized by hydrology. The butterfly’s distribution is therefore a map of seep and spring locations where all the required elements coincide — a geography that the species can neither alter nor expand.
No critical habitat has been designated under the 2024 listing at the time of this profile.
Threats
Water diversion and groundwater pumping that reduce or eliminate the groundwater discharge sustaining seep complexes is the most acute threat. The relationship is direct: reduce the groundwater that feeds the seep, and the seep dries; the seep dries, and the violets die; the violets die, and the butterfly cannot reproduce. In the arid western Colorado landscape, groundwater is a managed resource and the interests of agriculture, ranching, and municipal supply routinely compete with the minimum groundwater levels that sustain seep-dependent ecosystems.
Cattle grazing in and around seep complexes degrades the vegetation by consuming or trampling the violet plants that larvae require and by compacting and disturbing the saturated soil substrate.
Invasive plants displace native violets and other native forbs in wet meadow habitats. Smooth brome, reed canarygrass, and other invasive grasses can convert diverse native wet meadow to monoculture, eliminating the host plants and floral diversity the butterfly requires.
Drought reduces the groundwater recharge that sustains seep flows. Multi-year drought cycles that are increasing in frequency and severity under climate change threaten to periodically disrupt seep hydrology at vulnerable sites.
Recovery & Conservation
USFWS listed the Nokomis fritillary as threatened in 2024. No critical habitat has been designated under the listing rule. Recovery planning for a species with fewer than 20 known sites must address both the specific threats at occupied sites and the challenge of identifying and potentially restoring additional sites.
Conservation at occupied sites involves managing cattle access to seep complexes — through fencing and water development that redirects cattle away from sensitive areas — and controlling invasive plants in the wet meadow substrate. Maintaining and restoring the natural hydrology of seep complexes requires working with the water users and land managers who control the groundwater and surface water systems that feed them.
What You Can Do
- Report observations of large fritillary butterflies in wet meadow, seep, and spring habitats in Mesa, Garfield, and Delta counties to iNaturalist and CPW. The silver spots on the hindwing underside, combined with the seep habitat context, can help confirm identification. Photographs of both wing surfaces are helpful.
- Support seep and spring conservation in western Colorado. Land trusts and CPW work to protect high-quality seep complexes; voluntary conservation easements on private land holding seep habitats are particularly valuable.
- Advocate for instream flow and groundwater protections that maintain the minimum groundwater levels sustaining seep-dependent habitats.
- Fence cattle out of seep complexes if you manage grazing land in western Colorado. Exclusion fencing around seeps and springs protects both butterfly habitat and water quality.
Sources
Species status, population data, and natural history drawn from:
- USFWS Species Profile: Nokomis Fritillary (primary source for listing status)
- Final Rule, Federal Register, 2024 — listing as threatened
- NatureServe Explorer: Speyeria nokomis nokomis (G4T2)
- Colorado Parks and Wildlife butterfly monitoring records
- Ferris and Brown (1981): Butterflies of the Rocky Mountain States
Last reviewed: January 2024