Example of a silver-bordered fritillary species
Moderate-
High
The population size of the silver-bordered fritillary (atrocostalis subspecies) in Washington is low and is considered to have a declining trend. This butterfly is recognized as a "Species of Greatest Conservation Need" in Washington due to its rare and restricted hostplants and habitat types, small number of isolated populations, limited range and distribution, and known threats to their habitats. Research is especially needed to understand and quantify specific habitat requirements, including vegetation structure, food plant size and density, and key habitat features.
Description and Range
Physical description
The silver-bordered fritillary is in the genus Boloria (lesser fritillaries). It has distinctive black line and dot patterning on its bright orange upperside, and a heavily-patterned underside with muted colored triangles. Wingspan is up to 2 inches. Fritillary larvae are generally dark with many bristled spines.
Ecology and life history
The silver-bordered fritillary (atrocostalis subspecies) is dependent on fen and Sphagnum bog sites located in the xeric steppe and open forests of the Columbia River Basin. Bogs in this region are small, mid-elevation patches dominated by Sphagnum moss species and other bog-specific herbaceous plants and shrubs. These species depend on violets for their hostplants, which are unknown violet species (genus Viola), likely marsh violet (V. palustris) and bog violet (V. nephrophylla). Hostplants feed caterpillars (larvae). Beyond their fen and bog habitat restriction, little is known of this silver-bordered fritillary’s habitat requirements.
Like other lesser fritillaries, the silver-bordered fritillary has two generations per year (spring and late summer). They are sedentary butterflies and do not migrate; instead, the species inhabits sites year-round (as egg, larva, pupa and adult). Adults emerge from their chrysalids (pupae) during both spring and late summer.
Males begin emergence first, followed by females; late season individuals are primarily or solely females. Weather influences butterfly emergence and flight period duration, with wet or cold conditions potentially delaying emergence.
Both males and females feed by using their long proboscis to sip floral nectar.
Male fritillaries seek mates using rapid patrolling and searching flight behavior. Females search for egg-laying sites by slowly flying and hovering above hostplants and then landing and crawling to inspect vegetation before depositing eggs singly.
In Boloria fritillaries, the first (spring) generation of eggs mostly develops quickly, resulting in the second (summer) generation. Larvae from this second generation develop slowly and are the overwintering form for these butterflies. Larvae feed nocturnally on their hostplant; this characteristic, along with bristled spines on their dark body and a gland that secretes defensive chemicals, protects them from predators.
Geographic range
The distribution of the silver-bordered fritillary (atrocostalis subspecies) is limited in part by their dependence on rare habitat types. Their distribution and abundance in Washington is characterized by low numbers of small, isolated populations. Declines in both the number and size of populations have been documented for this species.
Overall, the range of this species encompasses scattered populations in eastern Oregon, eastern Washington, northern Idaho, northwest Montana in the United States, and eastern British Columbia and western Alberta in Canada.
In Washington, the species has been detected in the following counties: Grant, Lincoln, Okanogan, Pend Oreille, Stevens, and Whitman. Surveys have been conducted to determine the current distribution of the silver-bordered fritillary in the northeastern part of the state. Little is known of the current status and distribution of the species in other portions of their range within the state.
For a map of range-wide distribution and conservation status of the silver-bordered fritillary species, check out NatureServe Explorer.
Climate vulnerability
Sensitivity to climate change
Moderate-
High
Silver-bordered fritillary (SBF) occupies micro-habitats within the rare and isolated ecological system: Rocky Mountain Subalpine-Montane Fen (RMSMF); wetland sites that exist within xeric steppe and open forests of the Columbia Basin in eastern WA. Climate sensitivity for SBF is driven both by likely impacts to their habitat and directly to butterfly life stages. Fen wetland systems exist within a narrow range of hydrological input and soil pH; any activity altering hydrological cycles, sedimentation, or nutrient inputs could negatively affect these systems through loss of peat and shifts in vegetation. Significant changes to hydrological cycles, nutrient inputs, and soil pH could be affected by precipitation shifts, drought, reduced snowpack, earlier snowmelt, and increased air and water temperatures. Adults and larvae are sensitive to bog/fen drying, prolonged inundation from flooding, and increases in water and air temperature. North Pacific Bog and Fen was identified in the WA 2015 SWAP as one of 5 ecological systems most vulnerable to climate change in Washington (Fig 5-8), and at that time, RMSMF was included in the NP bog and fen system. Warmer temperatures and precipitation shifts that drive reduced snowpack and altered flow regimes will likely lead to drying of fens used by this species. Drought and forest succession also degrade habitat by reducing violet abundance (larval host plant) and key nectar resources. Adults occur in late-summer, a season when flowering plants are in general least abundant, and SBF females rely on abundant available nectar for reproductive success; increased drought and temperatures likely reduce nectar availability. Increasing fire frequency and increasing winter flood risk may help maintain early successional habitat and the high violet abundance required by the silver-bordered fritillary. However, fire and flooding also cause adult and/or larval mortality.
Exposure to climate change
Moderate-
High
- Increased temperatures
- Reduced snowpack
- Altered flow regimes
- Altered fire regimes
- Increased amount and/or duration of flooding
- Increased frequency of temperature and precipitation extremes
- Drought
- Alterations in soil moisture recharge
- Sediment or nutrient loading from upstream flooding and erosion
Conservation
Conservation Threats and Actions Needed
- Invasive and other problematic species
- Threat: Invasive plants, those currently here, and many yet to come in the future, out-compete native grassland species, and otherwise make habitat unsuitable.
- Action Needed: Using herbicide, fire, and mechanical methods to restore meadows.
- Threat: Forest encroachment due to long-term fire suppression has reduced the amount and quality of habitat. Hostplant (violet species) is an herbaceous species, and the butterfly occupies open habitat.
- Action Needed: Removed invading trees and shrubs.
- Agricultural and aquacultural side effects
- Threat: Intensive livestock use may cause direct harm to the butterfly through trampling, and indirect harm by reducing host and nectar plant species and compacting soil
- Action Needed: Install fencing to carefully manage or prohibit livestock access to occupied riparian areas
See the Climate vulnerability section for information about the threats posed by climate change to this species.
Resources
References
Boggs, C. 2003. Environmental variation, life histories, and allocation in Butterflies: Ecology and Evolution Taking Flight. Boggs, C., W. Watt, and P. Ehrlich, eds. The University of Chicago Press. 737pp.
James, D. and D. Nunnallee. 2011. Life Histories of Cascadia Butterflies. Oregon State Univ. Press, Corvallis. 447pp.
Pyle, R.M. and C.C. LaBar. 2018. Butterflies of the Pacific Northwest. Timber Press. 461 pp.
Pyle, R. 1989. Washington butterfly conservation status report and plan. WDFW, Olympia. 216pp.
USFS-BLM. 2010. Species fact sheet: Silver-bordered fritillary. Prepared by The Xerces Society for Invertebrate Conservation. Portland, Oregon.