Fighting for the San Emigdio Blue

Earlier this month, Los Padres ForestWatch submitted a formal request to the U.S. Forest Service to place a critically threatened butterfly – the San Emigdio Blue – on the forest’s list of sensitive species. If our request is granted, it would be only the second butterfly species to appear on the list of sensitive species in the Los Padres National Forest, and would ensure that its habitat is protected from a variety of threats.

The San Emigdio Blue butterfly (Plebejus emigdionis) is a unique species found only in Southern California. It is unique in that females will only lay their eggs on three different species of saltbush when a particular species of ant (Fomica pilicornis) is present. The ant protects the caterpillars from being eaten by other ants and wasps, and in return, the caterpillar secretes sugar and amino acids for the ant to eat.

But even with these personal bodyguards, the species is struggling. Activities threatening the survival of this species include water diversion, off-road vehicle trespass, livestock grazing, vegetation clearing, land development, road work, and spread of invasive species. As a result of these many threats, San Emigdio butterfly populations are predicted to decrease 50-70% in the long-term.

Bouton_SEB 004

Image courtesy Bill Bouton.


Though the San Emigdio Blue butterfly is not a commonly-recognized species, entomologists and butterfly enthusiasts are concerned about its survival. As one goal of ForestWatch is to protect wildlife, we investigated whether there are any known populations of San Emigdio Blue butterfly in Los Padres National Forest. After much research, ForestWatch gathered confirmation that populations of the rare butterfly do indeed occur within the Los Padres (throughout the Mt. Pinos Ranger District in Ventura and Santa Barbara counties) and the viability of the populations are highly threatened. We also discovered that while the San Emigdio Blue butterfly appears on sensitive species lists for several other forests in California, it is noted as not occurring in the Los Padres National Forest and as a result populations within the Los Padres have no protection from many actions threatening the butterfly’s habitat.

Plebejus emigdionis

Image courtesy David Horner, SolarDarkroom Photography.


Consequently, ForestWatch recently submitted a petition to list the San Emigdio Blue butterfly as a sensitive species in the Los Padres National Forest. The addition of the San Emigdio Blue butterfly to the “Los Padres National Forest Sensitive Species List” would help protect San Emigidio Blue populations in the forest by confirming that any potential impacts to the butterflies or their habitat are evaluated and mitigated. It would also ensure the utilization of the best and most current information to inform land management decisions throughout the region.

There is no timeline for when the Forest Service has to decide if the San Emigdio Blue deserves sensitive species listing, but without the proper conservation procedure in place, we risk significant decreases that may warrant its listing as endangered. Thus, it is critical to provide the San Emigdio Blue with protections afforded by placement on the sensitive species list before federal actions threaten the viability of this species further.




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