San Francisco State University
Department of Geography

Geography 316:  Biogeography

The Biogeography of  the Smith's Blue Butterfly (Euphilotes enoptes smithi)

photographs by Howe (1975)

by Sarah Kamienski, Undergraduate SFSU, Geography 316 Fall 1999
 

Kingdom: Animalia
     Phylum: Arthropoda
          Class: Insecta
               Order: Lepidoptera
                    Family: Lycaenidae
                         Genus: Euphilotes
                              Species: Euphilotes enoptes smithi
 
 

Description of Species

   Euphilotes enoptes smithi , the Smith’s blue, is a small butterfly with a wing span of only one inch. The males are bright blue in color while the females are brown. Both sexes have a characteristic orange-red band across the hind wing and a light ground color on the underside (Arnold 1980).
 

Habitat

    The Smith’s blue is found only in the coastal sand dunes, grasslands and coastal mountains of Monterey County. Figure 1 maps the known colonies of Euphilotes enoptes smithi, compiled by Arnold (1983).
    The Smith’s blue is a subspecies of g. Euphilotes which is distributed from the Rocky Mountains to the West Coast in isolated, distinct populations. Habitats for g. Euphilotes  range from coastal sand dunes to rocky hillsides, at varying elevations from sea level to 3,350 meters (Arnold 1980). The distribution of g. Euphilotes is dependent upon the distribution of the host plant, g. Eriogonum, commonly known as buckwheat. g Eriogonum, a genus containing close to 250 species, is found in western North America, from Alaska to central Mexico and less frequently in the eastern U.S. and the Great Plains (Shields and Reveal 1988).


Natural History

    The Smith’s blue, like other species of g. Euphilotes, is limited to areas in which buckwheat is prolific. Smith’s blue rely on the buckwheat to shelter them from the cold wind and fog characteristic of this area in summer. The adults emerge in accordance with the blooming of the species Eriogonum latifolium and E. parvifolium. Butterflies that depend on the species E. latifolium emerge from mid-June until early August; while those that depend on E. parvifolium emerge from mid-July until early September (Arnold 1983). Adult males and females have a short life, spanning only one week. During that week, they spend most of their time on the buckwheat flowerheads perching, obtaining nectar and mating. The flower of the buckwheat is also used as a nursery and food supply for larva (Arnold 1983).
 As soon as the males emerge, they begin the desperate hunt for a mate before their time is concluded. The mating ritual is simple and elegant: Once a mate has been located, the male flutters his wings and nudges the female with his abdomen. If she is receptive, she flutters her wings and they dance melodically upon the flowerheads until she relinquishes herself to him (Arnold 1980). Single eggs are then placed on sepals of newly opened flowers or on mature buds within 24 hours of mating (Arnold 1980).  According to Arnold (1980) only one generation of offspring is produced per year. For the Smith’s blue, there are five larval instars in which one month is spent as a larva. The third, fourth and fifth instar larvae eat only the flowerheads of the Eriogonum and are attended to by ants (Arnold 1983). It is believed that in exchange for food, the ants give the larvae protection from predators and the elements.
 
 
Evolution

     Euphilotes is a taxonomically complex group. It consists of four sibling species found in western North America- E. rita, E. enoptes, E. battoides and E.bernardino – and are distinguishable by variations in male genitalia (Shields and Reveal 1988).  It is believed that  E.enoptes smithi evolved from the more primitive  E.rita (figure 2) and sequentially with a host plant- Eriogonum, commonly referred to as wild buckwheat (Shields and Reveal 1988). According to Shields and Reveal (1988), the evolution of g. Euphilotes follows that of its host plant- a phenomenon referred to as sequential evolution. It has been suggested that  g. Eriogonum first appeared during the Miocene epoch, about 20 mya but expanded rapidly in the American west during the Pleistocene epoch as the west increasingly became an arid region (Shields and Reveal 1988). Shields and Reveal believe that evolution of Euphilotes  postdates that of Eriogonum and radiated from central Asia, crossing the Bering land bridge to North America. Speciation in g. Euphilotes is a result of genitalia modification of butterflies using a single species of g. Eriogonum (Shields and Reveal 1988). The consequent dissemination of subspecies has been primarily allopatric speciation, in which new species arise in isolation from ancestral species. The host plant acts as an island in evolutionary time; the species of g. Euphilotes associated with a particular species of g. Eriogonum evolves to accommodate evolution in the plant, generally instigated by climatic changes. Scientists believe that the Smith’s blue is endemic to Monterey County because it evolved from another species of the genus Euphilotes in order to accommodate evolutionary changes in the host plant (Shields and Reveal 1988). As a subspecies of Euphilotes enoptes,  mating is contained within the particular subspecies. This is because when the subspecies evolved, the male genitalia changed to accommodate changes in the host plant (Shields and Reveal 1988). Therefore, different subspecies are no longer able to mate with each other and they are also specialized to a certain species of Eriogonum.
 
 
 
 

Distribution

Map of Distribution:

 
 
 

Other interesting issues

    In 1976, the United States Fish and Wildlife Service classified the Smith’s blue as an endangered species due to habitat destruction and general degradation (Arnold 1983). Their fragile habitat is being destroyed naturally by shifting sand, invasive species and also by humans, including off-road vehicles and heavy foot traffic. For these delicate butterflies, loss of habitat means loss of life because they depend so heavily on the species of wild buckwheat that grows in coastal Monterey County. A plan has been devised in order to conserve the habitat of the Smith’s blue. The conservation plan seeks to maintain existing populations through a program that consists of habitat preservation, rehabilitation and management (Arnold 1983).
 
 
 
 
 

Bibliography
Arnold, R.A. 1980. Ecological Studies of Six Endangered Butterflies (Lepidoptera, Lycaenidae): Island Biogeography, Patch Dynamics, and the Design of Habitat Preserves. Berkeley, Ca. University of California Press.

Arnold, R.A. 1983. “Conservation and Management of the Endangered Smith’s Blue Butterfly, Euphilotes enoptes smithi (Lepidoptera: Lycaenidae).” Journal of Research on the Lepidoptera 22(2): 135-153.

Howe, W.H. 1975. The Butterflies of North America. Garden City, NY. Doubleday & Company, Inc.

Shields, O., J.L. Reveal. 1988. “Sequential evolution of Euphilotes (Lycaenidae: Scolitantidini) on their plant host Eriogonum (Polygonaceae: Eriogonoideae).” Biological Journal of the Linnean Society 33(1): 51-93.
 
 
 

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