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Mission Blue Butterfly

Icaricia icarioides missionensis (Invertebrates)

Species Description

The Mission Blue Butterfly was first described in 1937 when the Twin Peaks area of San Francisco was still considered part of the “Mission” District. It is a small, quarter-sized member of the Lycaenidae family, or “gossamer-winged” butterflies. Male Mission Blue Butterflies are characterized by dark-bordered, silver blue to violet blue upper wings, while females have brown upper-wings with blue traces.

An adult Mission Blue Butterfly only lives for 6-10 days. During that time, the species tries to mate and lay eggs. Females deposit eggs, usually singly, on one of three species of perennial lupines: the silver lupine (Lupinus albifrons) the Lindley varied lupine (L. variicolor) and the summer lupine (L. formosus). Larvae hatch from the eggs 4-7 days later and begin a 3-week spree of munching on the inner parts of lupine leaves. The caterpillars then crawl down to the base of the lupine, where they remain dormant until the following spring. After pupation adults emerge to begin the cycle anew.

Mission Blue Butterfly larvae have an interesting relationship with certain ant species. When the larvae are feeding in the spring, the ants will stroke the larvae with the ants’ antennae, which causes the larvae to secrete a sugary fluid called honeydew. The ants crave this fluid and consume it. In return, it is believed that the ants protect the larvae from predators and parasites.

The Mission Blue Butterfly was protected by the Endangered Species Act at the same time as the San Bruno Elfin Butterfly: June 1, 1976. Habitat destruction, degradation, and fragmentation are the main reasons the species is imperiled: even in protected parklands, the Mission Blue Butterfly is threatened by ordinary park maintenance and recreational uses that harm the butterfly and its plant hosts.

Nonetheless, the Mission Blue Butterfly exists within the GGNP at Fort Baker in Marin County, and Milagra Ridge in San Mateo County. The butterfly flies from late March until mid-June, a good time to search for the species. Sometimes they make it easy for you: the species has the unique behavior of actually sitting on its lupine host for a while.

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Conservation Action Item

Restore Mission Blue habitat:
Volunteer in Marin or San Mateo Counties

The Mission Blue needs your help restoring the habitat it needs to survive. Join the GGNRA and the Golden Gate National Parks Conservancy restoring Mission Blue habitats in Marin and/or San Mateo Counties.

Big Year Competitors have reported 7 sightings and taken 6 actions to help this species recover so far this year.

Trips

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Comments

  1. Liam O'Brien — 06 March 2010 - 14:17

    Because I am competing in Big Year as well as leading two butterfly walks for the Mission Blue, it was important for my initial sighting to be above reproach. That occurred today when Lisa Michl of the Site Stewards/GGNRA lead those of us over who were interested to see a fresh caterpilar feeding. Got a kick to be able to list this sighting at the larval stage.


  2. Ann Connolly — 06 March 2010 - 18:29

    A wonderful sighting on only a second trip for me. I’ll join you on one of your trips Liam.


  3. Steve Price — 20 April 2010 - 13:56

    Witnessed the unusual when we watched a Mission Blue suck on mud. Susie Bennett initially identified the butterfly as a Mission Blue but after seeing its behavior felt it must be an Echo Blue. After sharing photos and reports with other experts, we did see a Mission Blue sucking mud!


  4. Kate — 21 April 2010 - 12:21

    Aren’t we lucky to have seen this behavior which hadn’t previously been observed? Note to Hayward teacher also on the calendar.


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