The large marble butterfly (Euchloe ausonides), from the family Pieridae (whites and sulphurs), is found in open habitats across western and northern North America.
There are 7 subspecies of Euchloe ausonides:
- Euchloe ausonides ausonides
- Euchloe ausonides coloradensis
- Euchloe ausonides insulanus
- Euchloe ausonides mayi
- Euchloe ausonides ogilvia
- Euchloe ausonides palaeoreios
- Euchloe ausonides transmontana
Euchloe ausonides adults are medium sized butterflies, measuring between 1 ½ to 2 inches across both wings. Females are generally slightly larger than males. Ventral coloration between the sexes is generally similar, with a complex of green swirls with white spots (“marbling”) across the entire hindwing. Veins tend to be yellower in shade compared to the surrounding green marbling. The ventral forewing is mostly white with a narrow black cell-end bar in the middle and light black speckling along the leading forewing edge. Forewing margins have variable amounts of light green and/or black patterning and black checkering on the fringes.
Eggs are laid by Euchloe ausonides females singly on leaf buds, flowers, stems, and leaves of host plants in the mustard family.
In most of its range, E. ausonides overwinters as a pupa and emerges as an adult between late March and early June in hotter regions including the foothills of the Sierra Nevada mountains, or from May to early July in the northern portion of the range, including Colorado, and at higher elevations in the Sierra Nevada mountains. In the Sacramento Valley, adults emerge between February and April, with a second flight between May and July that has now largely disappeared. In the far northern edge of the range adults can be found into early August.
Adults often nectar on flowers, with recorded nectar species of many colors. They may prefer yellow or white flowers, including those of its caterpillar food plants, and have also been noted visiting scat and mud.
Males often patrol linear features such as streams, valley bottoms, or berms in a straight-line flight. Adult males can glide a few meters at a time while searching for females, typically a few feet off the ground, and will rest with wings open or closed. Males are capable of traveling several hundred meters or more a day. Adults will spend overnight periods in grasses or woody shrubs.
Euchloe ausonides’ range is widespread across much of western North America and parts of the Upper Midwest, with records in the United States including southern and eastern Alaska, California, Colorado, Idaho, Montana, western Nebraska, central and northern Nevada, northern New Mexico, western North Dakota, northern Minnesota, Oregon, western South Dakota, Utah, Washington, and Wyoming, and the Isle Royale National Park in Michigan. Historical records in Canada include most of the Yukon Territory and British Columbia east of the Coast Range, the western Northwest Territories, western Nunavut, Alberta, southern Saskatchewan, southern Manitoba, and southern Ontario. Populations in western Canada, Washington and northern Oregon are all east of the crest of the Cascade Mountains, but extend west further south in the Siskiyou Mountains of southwest Oregon.
The endangered subspecies Euchloe ausonides insulanus was historically found on Vancouver Island and Gabriola Island, British Columbia, Canada, but was last seen in Canada in 1910 and was declared extinct by the Canadian government in 1999. Populations were discovered in 1998 on San Juan Island and subsequently on Lopez Island (now extirpated) in San Juan County, Washington, with a total of five distinct populations on these two islands, though only one population is currently extant.
Large marble caterpillars feed on various plants in the mustard family, and preferred habitats for the butterfly include grasslands and open meadows along with streamsides, berms, desert washes, beaches, canyons, sagebrush steppe, montane slopes, open tundra, and weedy flats.
Known Caterpillar Host Plants
The following plant species support at least one subspecies of Euchloe ausonides:
- Arabis furcata
- Arabis hirsuta
- Barbarea orthoceras
- Barbarea vulgaris
- Boechera atrorubens
- Boechera lyalli
- Boechera perennans
- Boechera pinetorum
- Boechera retrofracta
- Boechera sparsiflora
- Boechera spatifolia
- Boechera stricta
- Boechera suffrutescens
- Brassica napus
- Brassica nigra
- Brassica rapa
- Caulanthus lasiophyllus
- Descurainia californica
- Descurainia incana
- Descurainia incisa ssp. incisa
- Descurainia pinnata ssp. brachycarpa
- Descurainia sp.
- Erysimum capitatum
- Hirschfeldia incana
- Isatis tinctoria
- Lepidium ramosissimum
- Lepidium virginicum ssp. menziesii
- Raphanus sativus
- Sinapis arvensis
- Sisymbrium altissimum
- Sisymbrium linifolium
- Sisymbrium loeseli
- Sisymbrium officinale
- Turritis glabra
Known Nectar Plants
The following nectar plant species support at least one subspecies of Euchloe ausonides:
- Achillea millefolium
- Alcea rosea
- Amsinckia sp.
- Arabis sp.
- Arnica cordifolia
- Barbarea orthoceras
- Berberis repens
- Boechera stricta
- Brassica nigra
- Cardamine cordifolia
- Carduus sp.
- Cerastium arvense ssp. strictum
- Cirsium arvense
- Cirsium sp.
- Dichelostemma capitatum ssp. capitatum
- Draba stenoloba
- Erodium cicutarium
- Eruca vesicaria ssp. sativa
- Erysimum capitatum
- Eschscholzia californica
- Heterotheca villosa
- Mertensia lanceolata
- Packera cana
- Packera fendleri
- Physaria montana
- Plantago lanceolata
- Potentilla pulcherrima
- Prunus americana
- Ranunculus sp.
- Raphanus sativus
- Rubus sp. (blackberry)
- Senecio crassulus
- Senecio integerrimus
- Silybum sp.
- Sisyrinchium bellum
- Taraxacum officinale
- Thlaspi arvense
- Townsendia hookeri
- Trifolium pratense
- Turritia glabra
- Wyethia helenioides
Despite its widespread distribution, recent studies using long term monitoring data have ranked the large marble as one of the western butterfly species most at risk of extinction in the next 50 years.
Of critical concern is the type subspecies of the large marble butterfly, Euchloe ausonides ausonides, which is already absent throughout much of its former distribution and is in danger of extinction in almost the entirety of its present range. Once present throughout each county in the Sacramento Valley and San Francisco Bay regions and common in both urban and rural locations, recent observations are almost entirely absent from the Sacramento Valley (in some places, not recorded since at least 2005), and remaining E. a. ausonides populations are relegated to beachfront areas along the San Francisco Bay and in the foothills of coastal ranges and the Sierra Nevada. Multiple long-term butterfly population monitoring sites have documented the disappearance of this butterfly subspecies while the occurrence of E. a. ausonides in museum and photographic records in multiple regions has plummeted by over 80%.
In 2023, the Xerces Society petitioned the U.S. Fish & Wildlife Service to protect the E. a. Ausonides large marble type subspecies as Endangered in order to protect remaining populations from vanishing entirely. If listed, this would be the second subspecies of this butterfly to be protected as Endangered under the ESA. The island marble, Euchoe ausonides insulanus, was petitioned in 2002 and again in 2012, and received protection and critical habitat designation in 2020.
We requested that five additional subspecies of the large marble be protected as Threatened.
Large marble populations are threatened by widespread habitat degradation, introduced predators, pesticide exposure, effects of climate change, and inadequate regulation across the states in which it is found.
While this species has been recorded on federal, state, and regional conservation lands, there are no species-specific management activities aimed at protecting it. In addition, the habitat protection allotted from these managed areas cannot protect caterpillars and adults from emerging threats like increasing temperature or decreasing precipitation trends expected across much of the western United States. ESA listing for the large marble butterfly, especially in California, is needed to protect this butterfly from becoming a permanent victim of the dangers butterflies face across western landscapes.
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COSEWIC. 2000. COSEWIC Assessment and update status report on the Island Marble (Euchloe ausonides insulanus) in Canada. Committee on the Status of Endangered Wildlife in Canada.
Davenport KE, Stanford RE, Langston RL. 2007. Flight periods of California butterflies for “resident species,” subspecies, and most strays to the state. The International Lepidoptera Survey Newsletter 8:1–66.
Griesemer A, Lambert A, Potter A, Gray E, Shrum J, Combs J, Reagan K, Hamer M, Callaway T, Lieber T. 2021. Species biological report for Island marble butterfly (Euchloe ausonides insulanus) version 1.0. U.S. Fish & Wildlife Service, Portland, Oregon.
Guppy C, Shepard J. 2001. Large marble. Pages 159–161 in Guppy C, Shepard J, editors. Butterflies of British Columbia. UBC Press, Vancouver, British Columbia, Canada.
Scott JA. 1975. Movements of Euchloe ausonides (Pieridae). Journal of the Lepidopterists’ Society 29:24–31.
Scott JA. 1986. The Butterflies of North America: A Natural History and Field Guide. Stanford University Press.
Scott JA. 2020. Butterflies of the southern Rocky Mountains area, and their natural history and behavior. Papilio (N.S.) 27:1–391.
Shapiro AM, Manolis TD. 2007. Field Guide to Butterflies of the San Francisco Bay and Sacramento Valley Regions. University of California Press.
Kevin Burls, The Xerces Society for Invertebrate Conservation
