Rocky Mountain Dotted-Blue
Euphilotes ancilla (Barnes & McDunnough, 1918)
Family: Lycaenidae
Subfamily: Polyommatinae
Identification: Upperside of male is deep blue with wide black borders; hindwing orange band usually absent. Female brown with variably expressed marginal orange patch on the hindwing. Underside of both sexes is light blue-gray with black spots. Underside of forewing often suffused with smoky gray.
Wing Span: 5/8 - 1 inch (1.6 - 2.5 cm).
Life History: Dotted Blues usually stay near their host plants. Males patrol around the host plants all day to find females. Eggs are laid singly on flowers or buds; caterpillars eat flowers and fruits and are tended by ants. Chrysalids hibernate in leaf litter.
Flight: One flight; late April to early August depending on location and elevation.
Caterpillar Hosts: Various Eriogonum species, especially Sulphur-flower.
Adult Food: Flower nectar, especially from Eriogonum.
Habitat: Sun-exposed rocky slopes and flats with host plant colonies.
Range: Washington south to California and southern Alberta and Saskatchewan south through rockies and high plains to Wyoming, Colorado, Utah, and northwestern New Mexico.
Conservation: Not required for the species, but rare subspecies in Nevada require survey and assessment of threats from alien weeds.
NCGR: G5 - Demonstrably secure globally, though it may be quite rare in parts of its range, especially at the periphery. Subspecies shieldsi Austin and purpura Austin of Nevada are of high conservation concern because of their local nature and possible threat from invasive alien weeds such as cheatgrass.
Management Needs: Conserve habitats for rare subspecies and maintain host plant populations.
Comments: NULL
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Verified Sightings
Displaying 1 - 24 of 255 verified sightings
Observation date: Jul 01, 2012
Submitted by: RobSimpson
Region: Park County, Wyoming, United States
Verified by: J_Martineau
Verified date: May 14, 2025
Observation date: Jun 30, 2012
Submitted by: RobSimpson
Region: Park County, Wyoming, United States
Verified by: J_Martineau
Verified date: Mar 13, 2025
Observation date: Jun 30, 2012
Submitted by: RobSimpson
Region: Park County, Wyoming, United States
Verified by: J_Martineau
Verified date: Mar 13, 2025
Observation date: Jul 11, 2024
Submitted by: Cascade Colors
Region: Grand County, Colorado, United States
Verified by: mikefisher
Verified date: Aug 22, 2024
Observation date: Jul 08, 2024
Submitted by: Cascade Colors
Region: Summit County, Colorado, United States
Verified by: mikefisher
Verified date: Aug 22, 2024
Observation date: Jul 02, 2024
Submitted by: hasfitz5
Region: Washoe County, Nevada, United States
Verified by: Ken Davenport
Verified date: Jul 12, 2024
Observation date: Jun 26, 2024
Submitted by: k.d.stutzman
Region: Teton County, Wyoming, United States
Verified by: J_Martineau
Verified date: Jul 11, 2024
Observation date: Jun 23, 2024
Submitted by: Elija-dk_32
Region: Teton County, Wyoming, United States
Verified by: J_Martineau
Verified date: Jul 08, 2024
Observation date: Jun 15, 2024
Submitted by: taogirl
Region: Montrose County, Colorado, United States
Verified by: mikefisher
Verified date: Jul 04, 2024
Observation date: Jul 18, 2022
Submitted by: Cascade Colors
Region: Jefferson County, Colorado, United States
Verified by: mikefisher
Verified date: Jul 31, 2022
Observation date: Jul 01, 2022
Submitted by: Eric Hartshaw
Region: Douglas County, Colorado, United States
Verified by: mikefisher
Verified date: Jul 09, 2022
Observation date: Jun 26, 2021
Submitted by: Robb Hannawacker
Region: San Juan County, Utah, United States
Verified by: RaisingButterfl...
Verified date: Dec 16, 2021
Observation date: Jul 03, 2018
Submitted by: MTmariposa
Region: Missoula County, Montana, United States
Verified by: J_Martineau
Verified date: Aug 01, 2021
Observation date: Jun 20, 2021
Submitted by: NBBAM
Region: Boulder County, Colorado, United States
Verified by: mikefisher
Verified date: Jul 24, 2021
Observation date: Jun 13, 2021
Submitted by: Dwaine Wagoner
Region: Natrona County, Wyoming, United States
Verified by: J_Martineau
Verified date: Jun 16, 2021
Observation date: Jun 25, 2014
Submitted by: chherrmann
Region: Clark County, Nevada, United States
Verified by: Ken Davenport
Verified date: Jun 14, 2021
Observation date: Jun 23, 2020
Submitted by: WYbutterflyer1
Region: Albany County, Wyoming, United States
Verified by: J_Martineau
Verified date: Feb 08, 2021
Observation date: Jul 06, 2020
Submitted by: meister
Region: Garfield County, Colorado, United States
Verified by: mikefisher
Verified date: Nov 08, 2020
Observation date: Jun 23, 2020
Submitted by: Dwaine Wagoner
Region: Natrona County, Wyoming, United States
Verified by: J_Martineau
Verified date: Jun 25, 2020
Observation date: Jun 01, 2020
Submitted by: joeleahy
Region: Jefferson County, Colorado, United States
Verified by: A_baldini
Verified date: Jun 06, 2020
Observation date: Jul 21, 2019
Submitted by: stevecary
Region: Gilpin County, Colorado, United States
Verified by: mikefisher
Verified date: May 30, 2020
Observation date: Jul 19, 2019
Submitted by: stevecary
Region: Gilpin County, Colorado, United States
Verified by: mikefisher
Verified date: May 30, 2020
Observation date: Jul 11, 2019
Submitted by: stevecary
Region: Lake County, Colorado, United States
Verified by: mikefisher
Verified date: May 30, 2020
Observation date: Jun 29, 2019
Submitted by: A_baldini
Region: Larimer County, Colorado, United States
Verified by: mikefisher
Verified date: Oct 04, 2019
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