Blues: Sand Mountain blue (Euphilotes pallescens arenamontana)

(Lepidoptera: Lycaenidae: Polyommatinae)

Profile prepared by The Xerces Society for Invertebrate Conservation

The Sand Mountain blue butterfly (Euphilotes pallescens arenamontana) is a highly geographically restricted subspecies that only lives in Sand Mountain Recreation Area in the Great Basin of Nevada. Habitat for this species has suffered destruction and modification by extensive off-road vehicle (ORV) use over the past three decades. Current and proposed management of the species’ habitat by the Bureau of Land Management allows ORV use in the overwhelming majority of the areas known to harbor the species. Off-road vehicles are an immediate threat to these butterflies and there are no regulatory mechanisms to protect them or their habitat. Without the designation as an Endangered Species, the Sand Mountain blue butterfly faces an imminent threat to its continued existence in the wild.

conservation status

The Xerces Society, the Center for Biological Diversity, the Nevada Outdoor Recreation Association, and Public Employees for Environmental Responsibility filed a listing petition on Friday, April 23, 2004, to protect the Sand Mountain blue butterfly (Euphilotes pallescens arenamontana). The petition calls on the US Fish and Wildlife Service (USFWS) to list the butterfly as a threatened or endangered species under the Endangered Species Act.

description

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Adult

The adult Sand Mountain blue butterfly is small, with a wingspan of slightly less than one inch across when fully spread. Males of the species average 11.1 mm (10.0 – 11.8); females are slightly smaller at 10.9 mm (10.0 – 11.9). E. p. arenamontana is the palest sub-species of the Euphilotes genus. The distally whitish dorsum and pinkish aurora are also distinct traits in the subspecies. E. p. arenamontana differs from E. p. pallescens by the non-contrasting wing bases at the distal areas. The ventral surfaces of the two subspecies are said to be similar but the black macules on E. p. arenamontana are usually smaller (Austin, 1998).

Male

The males’ have a pale bluish violet dorsum that is nearly whitish towards the distal edges. The outer margin of the wing is narrow (0.5 mm) and black, sometimes no more than a terminal line on the forewing and a series of black dots on the hindwing. The fringes are white with gray checkering behind the vein tips on both wings. The ventral surface is chalky white; the macules are small, and nearly obsolete on the hindwing. The moderately wide aurora on the hindwing is pale orange (Austin, 1998).

Female

The females’ dorsum is brown to tan and only similar to the males’ bluish coloring at the bases on both wings. The forewing possesses a brown cell-end bar, and the apex is typically whitish. The hindwing has black dots along the margin, and the aurora on the hindwing is pale orange to pale pink, usually becoming nearly white distally and not strongly contrasting. The fringes and the ventral surface are the same as found on the males of the subspecies (Austin, 1998).

Immature

The larvae of the Sand Mountain blue butterfly are fat and grub- like, with lateral setae. Like other blue butterflies, the Sand Mountain blue larvae are very colorful (CBD et al. 2004).

taxonomic status

The Sand Mountain blue butterfly (Euphilotes pallescens arenamontana) is in the family Lycaeninae, the family that includes the blue, copper, gossamer-winged, hairstreak, and harvester butterflies, within the order Lepidoptera of the Kingdom Animalia and the Class Insecta (Austin, 2002). The taxon is named after its type locality and the only known place of its occurrence; arenamontana is derived from the Spanish words for Sand Mountain (arena= sand, montaña=mountain).

life history

Sand Mountain blue butterflies are closely linked to their larval host plant, Kearney buckwheat, also known as Money Buckwheat, (Eriogonum nummulare M.E. Jones), throughout their life (Austin, 1998). In this area of Nevada this plant grows primarily near the southern dunes on Sand Mountain. This plant is the sole food source for the larvae and an important nectar source for adults during their flight period (Opler, 1999). The plant also provides cover and a layer of litter on the ground where pupae mature. Emergence generally coincides with the peak flowering of the host plant and occurs between mid-July and mid-September. The Sand Mountain blue butterfly only lives about one week as an adult and the overall population of adults is active for only a few weeks.

The Sand Mountain blue is only known to exist at Sand Mountain. Its absence in other dunes nearby, such as Blow Sand Mountain, suggest that this butterfly requires a large area of the Buckwheat.

Life cycle

The subspecies produces one brood a year and the ma turation of larvae is timed in accordance with the peak blooming of its host plant, Kearney buckwheat (Austin, 1998). The female butterfly lays single eggs into buckwheat flower heads within 24 hours of mating. In about a week the egg hatches and becomes a larva. The larvae feed on petals and fruit in the flower head.

The larvae are also known to produce a secretion of sugar from the abdominal glands that provides food for their attendant ant species, the desert carpenter ants. In return, the larvae are thought to derive some protection from predation or parasitism from the ants, but this remains uncertain (CBD et al. 2004). The larvae mature through several larval stages called instars in three to four weeks before becoming a pupa. The pupa eventually falls into leaf litter and topsoil beneath the plant. Pupae diapause for the winter (Austin, 1998).

This species is non-migratory and movement has been observed to be restricted to within 200 feet of the host plant (Opler, 1995).

Host plant

Kearney buckwheat is a long-lived perennial shrub with an extensive branching caudex deriving from a woody taproot. The caudex adjusts to the shifting dune sand and the flexible aboveground branches can occasionally be found downslope from the taproot (Reveal, 2002). Kearney buckwheat has deep roots and an ability to survive sand movement. These plants often form hummocks, mounds of sand held in place by roots and stems, which are important stabilizers of blowing sand (Bury and Luckenbach, 1983). Leaves are formed in the spring and early summer and when exposed, the caudex also becomes photosynthetic. Flowering begins in early summer and continues until a killing frost; fruit production is likewise continuous. Kearney buckwheat is widespread in Nevada, occurring along the western third of the Great Basin desert and in a total of eight Nevada counties, from 3700-6100 ft. in elevation (Reveal, 2002). It is not considered threatened, rare, or at risk in Nevada (NNHP, 2003). Kearney buckwheat also occurs in Utah, Arizona, and California (USDA 2002). Natural causes of mortality include foraging chipmunks and droughts; however the mature Kearney has such an extensive root system that drought will only have a considerable impact on germinating plants. The most destructive unnatural cause of mortality in the San Mountain area comes from ORV impact.

distribution

The only known habitat for the Sand Mountain blue butterfly is on the Sand Mountain dunes within the Sand Mountain Recreation Area, Bureau of Land Management, 10 Churchill County, Nevada. All type specimens were collected from this locality (U.S. highway 50, Sand Mountain, 1310 m, T17N R32E S28 on USGS Fourmile Flat, Nev. 7.5’ quadrangle) (Austin, 1998).

threats and conservation needs

The Sand Mountain blue depends entirely on approximately one thousand acres of Kearney buckwheat shrub habitat at Sand Mountain in the Great Basin east of Fallon, Nevada. This area is intensively impacted by off-road vehicles (ORVs), which can kill these butterflies and their host plant (the buckwheat).

Sand Mountain Recreation Area (SMRA) consists of 4,795 acres of BLM public land that is open to unrestricted off-road vehicle use.During the last decade (1993 to 2003), the BLM reported a 25 percent increase in visitor use at the recreation area. ORV use is still going up. Much of the Kearney buckwheat habitat that once thrived adjacent to the dunes has been destroyed in the past five years by ORV users, who now ride not only through the dunes but also over the shrubs themselves.Last spring, BLM biologists recommended closing the best remaining habitat at Sand Mountain to vehicles in order to protect the butterfly, the buckwheat, and several other rare endemic species.But BLM managers decided to adopt a voluntary system only.

After nearly four months of monitoring, the BLM has concluded that these voluntary measures are not working. Educational efforts and increased signage are routinely ignored as off-roaders leave the routes, often running over posted signs and using the Kearny buckwheat as ORV jumps.

The existing measures are undoubtedly ineffective. Unless more successful measures are put in place, the Sand Mountain blue butterfly’s habitat will be completely destroyed.

“It is unfortunate that the BLM and ORV riders are unwilling to protect the last one thousand acres of habitat for the Sand Mountain blue,” said Scott Hoffman Black, Executive Director of the Xerces Society, “We now have no choice but to take this to the next level and protect this butterfly and its habitat through the Endangered Species Act.”

references

Austin, G.T. 1998. New subspecies of Lycaenidae from Nevada and Arizona. Pages 539- 572 in T.C. Emmel, editor. Systematics of Western North American Butterflies. Mariposa Press, Gainesville, Florida.

Austin, G.T. 2002. Personal Communication with BLM’s Claudia Funari.

Bury, R.B. and R.A. Luckenbach. 1983. Vehicular Recreation in Arid Land Dunes: Biotic Responses and Management Alternative. Pages 207-221 in R.H. Webb and and H.G. Wilshire, editors. Environmental Effects of Off-Road Vehicles. Springer-Verlag, New York, NY.

Center for Biological Diversity, The Xerces Society for Invertebrate Conservation, Public Employees for Environmental Responsibility, and the Nevada Outdoor Recreation Association. 2004. Petition to list the Sand Mountain Blue Butterfly (Euphilotes pallescens arenamontana) as a threatened or endangered species under the U.S. Endangered Species Act.

Nevada Natural Heritage Program, Dept. of Conservation and Natural Resources Webpage. http://heritage.nv.gov/reports.htm accessed Nov 20, 2003

Opler, Paul A. and Amy Bartlett Wright. 1999. A Field Guide to Western Butterflies. Second Edition. Houghton Mifflin Company, New York.

Reveal, James L. University of Maryland. Personal Communication via E-mail with Dean Tonenna, Sep. 18, 2002.

USDA, NRCS. 2002. The PLANTS Database, Version 3.5. National Plant Data Center, Baton Rouge, LA 70874-4490 USA.

additional resources

petition to list this species under the federal Endangered Species Act

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