Pacific Southwest Region
California, Nevada and Klamath Basin

Thorne's Hairstreak Butterfly Warrants Review for Possible Protection Under the Endangered Species Act

Apr 02, 2010

April 2, 2010
Contact: Jane Hendron, Carlsbad Fish and Wildlife Office - 760/431-9440 ext. 205 

Thorne’s Hairstreak Butterfly Warrants Review for Possible Protection Under the Endangered Species Act

Carlsbad, CA - The U.S. Fish and Wildlife Service (Service) announced today its 90-day finding on a 2004 petition to list the Thorne’s hairstreak butterfly (Callophrys [Mitoura] grynea thornei or Callophrys [Mitoura] thornei) under the Endangered Species Act contains substantial information indicating listing may be warranted. The Service will now conduct an in-depth status review of the butterfly. 

The Thorne’s hairstreak butterfly is found exclusively in the Otay Mountain area in southern San Diego County, California. Potential threats to the butterfly may be attributable to the following factors: wildfire and habitat fragmentation; inadequacy of existing regulatory mechanisms; and natural or manmade threats, including effects of wildfire on individuals and vulnerability of small, isolated populations. 

The butterfly was previously petitioned for listing in 1991 and 2004; both findings were determined to be not substantial. The Center for Biological Diversity and David Hogan challenged the Service’s negative finding on the 2004 petition that was published on August 8, 2006. A settlement agreement was reached whereby the Service agreed to review the 2004 petition again, and to look at any new information about the butterfly and its habitat that has since become available. 

Under the Endangered Species Act, the Service is required to review a petition to list, delist, or reclassify species, and determine whether it contains substantial information indicating the petitioned action is warranted. The first step in the process is known as a 90-day finding.

Comments and information on the 90-day petition finding may be submitted electronically to, or by hand delivery or mail to: Public Comments Processing, Attn: FWS-R8-ES-2010-0016 Division of Policy and Directives Management, U.S. Fish and Wildlife Service, 4401 N. Fairfax Drive, Suite 222, Arlington, VA 22203. We will not accept faxes, and all comments received will be posted on

Comments will be accepted until June 4, 2010. 

A copy of the 90-day finding is available online today at the Federal Register. The official copy will be published on April 5, 2010, and can be accessed at, or, or may be obtained by contacting the Carlsbad Fish and Wildlife Office at 760-431-9440. 

Thorne’s hairstreak butterfly has rich reddish brown wings with dark brown shading and lays its eggs only on the larval host plant, Tecate cypress, found primarily on north-facing slopes and along moist canyons and drainages from near sea level to over 4,200 feet in elevation.

The butterfly’s larval habitat occurs almost entirely on publicly owned property – Bureau of Land Management (BLM), City of Chula Vista and California Department of Fish and Game.  Currently, there are about 454 acres of Tecate cypress habitat most of which occurs on BLM managed lands. 

The Service is soliciting information about the butterfly and its habitat from governmental agencies, Native American Tribes, the scientific community, industry, and other interested parties. Based on the status review, the Service will make one of three possible determinations: (1) listing is not warranted, in which case no further action will be taken; (2) listing as threatened or endangered is warranted and a proposed rule will be published; or (3) listing is warranted but precluded by other, higher priority activities.  

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