Listing
Oct 14, 1975
Oct 14, 1975 Listing (Endangered)
Proposed Endangered Status for 6 Species of Butterfly in California; 40 FR 48139 48140 (San Bruno el…
- Publication type: Proposed
Item 1
FWS Focus
Overview
Characteristics
Overview
The San Bruno elfin is a small butterfly with a wingspan of 2.0 to 2.4 centimeters. In adults of both sexes, the wings are brown on the upperside and reddish brown on the underside with a whitish, irregular median line. The adult flight period is late February to mid-April. Eggs are laid in small clusters or strings on the upper or lower surface of the larval hostplant, broadleaf stonecrop (Sedum spathulifolium). Typical habitat is coastal grassland and low scrub of north-facing slopes within the fog belt where the larval host plant grows. All known locations are restricted to San Mateo County, California, where several populations are known from San Bruno Mountain, Milagra Ridge, the San Francisco Peninsula Watershed and Montara Mountain.
The butterfly was listed as endangered on June 1, 1976.
The butterfly continues to be threatened by:
- Public infrastructure development
- Climate change
- Illegal collection
- Habitat modification by non-native plant species
- Parasitism and predation of larvae potentially exacerbated by non-native Argentine ants
- Pesticides
- Small populations
- Trampling larval host plants during population monitoring
Scientific Name
Callophrys mossii bayensis
Common Name
San Bruno elfin Butterfly
FWS Category
Insects
Identification Numbers
Characteristics
Characteristic category
Habitat
Characteristics
Habitat
Characteristic category
Physical Characteristics
Characteristics
Size & Shape
The San Bruno elfin is a small butterfly with a wingspan of 2.0 to 2.4 centimeters.
Color & Pattern
In adults of both sexes, the wings are brown on the upperside, and reddish brown on the underside with a whitish, irregular median line. Larvae are dichromatic, either red or yellow.
Characteristic category
Life Cycle
Characteristics
Life Cycle
Adults are highly sedentary and move less than 100 meters on average and no more than 800 meters from their larval host plant. Larvae emerge in five to seven days and feed on the stonecrop host plant. The developing larvae have a mutualistic relationship with native ants that defend the larvae from predation and parasitism in return for honeydew secreted by the larvae. However, this mutualistic relationship with native ants may be disrupted by the presence of non-native Argentine ants resulting in increasing rates of predation and parasitism of larvae. Larvae complete their development in late May or early June and enter the pupal phase. Pupation occurs among the loose soil and litter of the host plant stonecrop’s roots. The pupal stage lasts from June until the following March.
Reproduction
The adult flight period is late February to mid-April. Eggs are laid in small clusters or strings on the upper or lower surface of the larval hostplant, broadleaf stonecrop (Sedum spathulifolium).
Characteristic category
Food
Characteristics
Food
The butterfly’s larval host plant is broadleaf stonecrop (Sedum spathulifolium). The preferred nectar source for adults is common lomatium. Adults may drink the nectar of early-blooming coastal flowers, especially hog fennel, using a long tube called a proboscis that extends from the underside of the head.
Timeline
Explore the information available for this taxon's timeline. You can select an event on the timeline to view more information, or cycle through the content available in the carousel below.
10 Items