Species Profile

Nuttall's Sheep Moth

Scientific Name: Hemileuca nuttalli
Other/Previous Names: Hemileuca nuttallii
Taxonomy Group: Arthropods
Range: British Columbia
Last COSEWIC Assessment: November 2015
Last COSEWIC Designation: Endangered
SARA Status: No schedule, No Status

Individuals of this species may be protected under Schedule 1 under another name; for more information see Schedule 1, the A-Z Species List, or if applicable, the Related Species table below.

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Quick Links: | Description | Habitat | Biology | Threats | Protection | National Recovery Program | Documents

Image of Nuttall's Sheep Moth


Nuttall’s Sheep Moths (Hemileuca nuttalli) are large members of the wild or giant silk moth family (Saturniidae). Adults of both sexes have forewing lengths of 32-39 mm with white to pale yellow forewings and bright yellow hindwings framed by a pattern of thick black markings. Larvae are spiny and black, with the final instars approximately 50 mm in length. (Updated 2016/12/20)


Distribution and Population

The global range of Nuttall’s Sheep Moth is from the extreme southern portion of the Okanagan Valley in British Columbia, southward to northern Arizona and New Mexico. In Canada, it has been recorded from the south Okanagan Valley from three general areas: 1) Osoyoos, 2) Oliver (precise site unknown), and 3) Vaseux Lake. The most recent records for the species are 2002 near Vaseux Lake and 1986 at Haynes’ Lease Ecological Reserve (approximately 8 km north of Osoyoos). It is unknown if the Haynes’ Lease occurrence is the same location as historical records labelled ‘Osoyoos’ and the precise location of the Oliver record is unknown. Targeted surveys for adults at six sites in 2009 and for larvae at 16 sites in 2014 were unsuccessful. The targeted searches in 2014 included the 2002 site. (Updated 2016/12/20)



In Canada, Nuttall’s Sheep Moth is found in the bunchgrass shrub-steppe on dry, open slopes at low elevations where the only known Canadian larval host plant, Antelope-brush (Purshia tridentata), is most abundant. The main habitat is the Antelope-brush/Needle and Thread Grass plant community, which is fragmented by habitat loss; less than 33% of its historical mapped distribution remains in approximately 3200 ha in the Okanagan Valley. (Updated 2016/12/20)



Nuttall’s Sheep Moth is univoltine and may have a life cycle that spans 1 – 2 years. The eggs are laid on the host plants in late summer and overwinter, typically hatching in late April or May the following spring. Early instar larvae are gregarious, while later instar larvae are solitary. The 5th instar larva creates a cocoon in leaf litter or a shallow burrow, and the adult emerges later that season or possibly the following year. In Canada, the known flight period is August through early September, although individual moths have shorter life spans (adults do not feed). Adults are diurnal with a peak of activity in the afternoon, and both sexes are rapid, fast fliers. Perched females emit pheromones to attract potential mates. (Updated 2016/12/20)



Cumulative habitat loss, degradation, and fragmentation from agriculture (mainly vineyards and orchards) as well as residential and commercial development are the most significant threats to Nuttall’s Sheep Moth populations in Canada. (Updated 2016/12/20)



Federal Protection

Provincial and Territorial Protection

To know if this species is protected by provincial or territorial laws, consult the provinces' and territories' websites.



PLEASE NOTE: Not all COSEWIC reports are currently available on the SARA Public Registry. Most of the reports not yet available are status reports for species assessed by COSEWIC prior to May 2002. Other COSEWIC reports not yet available may include those species assessed as Extinct, Data Deficient or Not at Risk. In the meantime, they are available on request from the COSEWIC Secretariat.

4 record(s) found.

COSEWIC Status Reports

Response Statements

  • Response Statement - Nuttall's Sheep Moth (2017)

    This large, showy and conspicuous moth is restricted to Antelope-brush habitat in the Okanagan Valley of British Columbia. That habitat type has declined considerably in quality and extent in the past century and remains under threat due to continued conversion to viticulture, residential and commercial development, and impact of wildfires. This is a rare moth in Canada: very few have been observed since the first record in 1920. Potentially large fluctuations in the population size may affect its long-term viability.

COSEWIC Annual Reports

  • COSEWIC Annual Report - 2015-2016 (2016)

    Over the past year COSEWIC re-examined the status of 25 wildlife species; of these, the majority (68%) were re-assessed at the same or lower level of risk. Of a total of 45 species assessed, seven were assigned a status of Not at Risk (two re-assessments and five new assessments). To date, and with the submission of this report, COSEWIC’s assessments now include 724 wildlife species in various risk categories, including 320 Endangered, 172 Threatened, 209 Special Concern, and 23 Extirpated (i.e., no longer found in the wild in Canada). In addition, 15 wildlife species have been assessed as Extinct, 54 wildlife species have been designated as Data Deficient, and 177 have been assessed and assigned Not at Risk status.

Consultation Documents

  • Consultation on Amending the List of Species under the Species at Risk Act: Terrestrial Species - January 2017 (2017)

    The Government of Canada is committed to preventing the disappearance of wildlife species at risk from our lands. As part of its strategy for realizing that commitment, on June 5, 2003, the Government of Canada proclaimed the Species at Risk Act (SARA). Attached to the Act is Schedule 1, the list of the species provided for under SARA, also called the List of Wildlife Species at Risk. Extirpated, Endangered and Threatened species on Schedule 1 benefit from the protection afforded by the prohibitions and from recovery planning requirements under SARA. Special Concern species benefit from its management planning requirements. Schedule 1 has grown from the original 233 to 521 wildlife species at risk. In 2016, on the recommendation of the Minister of the Environment, the Governor in Council approved listing proposals for 44 wildlife species. It is proposed that 23 species be added to Schedule 1, 18 be reclassified or have a change made to how they are defined (two wildlife species are being split into four), one species  be removed from Schedule 1, and another two species not be added. Listing proposals were published in Canada Gazette, part I for a 30-day public comment period and final listing decisions for all 44 species are expected in the first half of 2017.Please submit your comments byMay 11, 2017, for terrestrial species undergoing normal consultationsand byOctober 11, 2017, for terrestrial species undergoing extended consultations.For a description of the consultation paths these species will undergo, please see:Species at Risk Public Registry website The COSEWIC Summaries of Terrestrial Species Eligible for Addition or Reclassification on Schedule 1 - January 2017