San Francisco State University
Department of Geography

Geography 316: Biogeography

The Biogeography of the Mission Blue Butterfly (Icaricia icarioides missionensis)

By Joseph Melton, Undergraduate SFSU, Geography 316, Autumn of 2000

Kingdom: Animalia

Phylum: Arthropoda

Class: Insecta

Order: Lepidoptera

Family: Lycaenidae

Genus: Icaricia

Species: Icarioides missionensis

Common Name: Mission Blue Butterfly

Binomial Name: Icaricia icarioides

Scientific Name: Icaricia icarioides missionensis

Description of Species:

Icaricia icarioides missionensis, the Mission blue butterfly, makes its adult appearance between early March and early July. The Mission blue is a small butterfly with a wingspan ranging from 2.5 to 3.6 cm (1-1½ in). Figure 1 displays the upper and lower wings of the male and female Mission blues. The male of the species is distinguished with white fringe, and a dark (black) border with silver blue to violet blue upperwings. The female, conversely, displays dull brown upper wings, with only small traces of blue. The underwings of both the male and female appear silver gray or brownish, with black speckles (Arnold 1994).

Habitat:

Icaricia icarioides missionensis are currently restricted to three locations in the San Francisco Bay Area, including—the Twin Peaks area of San Francisco; Fort Baker in Marin County; and San Bruno Mountain in San Mateo County. The latter hosts the largest population of Mission blue butterflies. Mission blues are found commonly at elevations around 700 ft (Arnold 1994).

The Mission blue butterfly requires the type coastal scrub and grassland habitat found only near the Golden Gate of San Francisco. In this environment the Mission blue strictly depends on any of three species of perennial lupine to reproduce—Lindley varied lupine (L.variicolor), Silver lupine (L. albifrons), or Summer lupine (L. fomosus). Figure 2 displays Summer lupine (L. fomosus). Mission blues require one of these three species of lupine to lay their eggs, for the nourishment of larvae, and from which adult Mission blues emerge. Without the lupine the Mission blue cannot reproduce, and thus cannot survive (Arnold 1994).

Natural History:

A new generation of Icaricia icarioides missionensis appears annually. The Mission blue butterflies make their adult appearance between early March and early July in harmony with the blooming of flowers they depend on for nectar (Arnold 1994).

Daily adult behavior includes foraging for nectar, perching, flying, mating, and for females, laying eggs. Almost equal time is split between perching, feeding, and flying (Arnold 1983). Once mating has taken place, females deposit single eggs onto the leaves, stems, flowers, and seedpods of one of three types of perennial lupines: Lindley varied lupine (L. variicolor), Silver lupine (L. albifrons), or Summer lupine (L. formosus) (Arnold 1994). Larvae hatch from the eggs after 4-7 days and begin feeding on the mesophyll of the host lupine for a period of about three weeks (Arnold 1983). Next the caterpillars crawl down into the fallen leaves at the base of the host lupine where they go dormant until the following spring. When dormancy ends in spring, the caterpillars ascend the host lupines to feed until pupation. At pupation the caterpillars again descend the host lupine, where they eventually emerge as adult Mission blue butterflies and the cycle begins anew—foraging, perching, mating, the laying of eggs, pupation, and the emergence of the adult (Arnold 1994). Figure 3 shows the adult male Mission blue butterfly and the Mission blue larvae.

Evolution:

According to Scott (1986), butterflies probably first appeared in the tropical areas of Africa, America, and Eurasia about 100-80 million years ago. At that time, South America still touched Africa, Africa barely touched Eurasia (along Spain), and Europe was still attached to northern North America. Because of this geographic orientation of the continents butterflies were thus able to disperse throughout these areas. India and Madagascar were too far away from Africa, and it is believed that few if any butterflies reached these areas. Australia was even further away and most likely did not harbor butterflies at that time. The line of ancestry producing butterflies can most likely be traced from a single bacterium-like creature that evolved from a primordial goo, rich in organic compounds about 3.5 to 3.0 billion years ago. The branch of the evolutionary tree that butterflies decended from produced lamp shells, bryozoans, mollusks, segmented worms, and eventually butterflies. The order Lepidoptera may be the most recently evolved of all the insect orders, save for fleas (Scott 1986). The Family Lycaenidae is divided into three subfamilies—Theclinae (the haristreaks), Lycaeninae (the coppers), and Icaricia (the blues). The Theolinae subfamily evolved in a tropical climate, while Lycaenidae and Icaricia evolved in temperate climate zones (Howe 1975).

The genus Icaricia exhibits extraordinary variation within and among the populations, as well as through time and space. The genus is host to 12 species, including I. icarioides, I. evius, I. moroensis, I. missionensis, I. padalis, I. pheres, I. ardea, I. lycea, I. bucholzi, I. pembina, I. blackmorel, and I. montis (Howe, 1975).

Distribution:

The Family Lycaenidae has a wide distribution. The family is found on all continents except Antarctica.

The genus Icaricia is limited in distribution to western North America, west of the Great Plains, appearing in discontinuous populations. The genus Icaricia occurs from northern Baja California and Arizona north to Alaska and at elevations ranging from sea level to over 12,000 ft (Howe 1975). The distribution of the genus is restricted by the location of the plant genus Lupinus, with over forty species and subspecies of the plant found through out the temperate climate of Pacific Northwest America. The distribution map (Figure 4) of the Mission Blue species shows its extreme restriction, and its disjunct distribution. Icaricia icarioides missionensis can only be found in the San Francisco Bay Area of California where three specific types of the plant genus Lupinus are found (L. variicolor, L. albifrons, and L. formosus). With the decimation of the majority of its habitat on the San Francisco and Marin Peninsulas, the Mission blue butterfly now resides in a few isolated areas. In general, they can be found within the Golden Gate National Recreation Area (GGNRA), which begins where the San Francisco Bay meets the Pacific Ocean, extending north and south along the Pacific shoreline (La Pierre 1998). Specifically, they are found in the Twin Peaks area and in McClaren Park in San Francisco County, at Fort Baker in Marin County, and on San Bruno Mountain in San Mateo County. The San Bruno population is the largest (La Pierre 1998).

Other interesting Stuff:

Status of the Mission blue butterfly: Much of the Mission blue butterfly’s habitat of coastal scrub containing the crucial plant genus Lupinus has been destroyed. The San Mateo County town of Brisbane resides in what was once probably the prime habitat of the Mission blue. Many things have contributed to habitat decline. Near Brisbane an industrial park and a rock quarry have contributed to habitat declination. In general, the most crucial negative affect on the Mission blue’s habitat is residential and industrial development, which, have helped to reduce suitable coastal scrub habitat of the Mission blue. Other habitat destruction comes from cultivation, grazing, and the proliferation of indignant, aggressive, exotic (non native) plants, such as European gorse and pompous grass. The Mission blue butterfly was added to the list of endangered species in 1976. In 1984 a recovery plan, drawn up by the U.S. Fish and Wildlife Service (USFWS) outlined the need to protect Mission blue habitat and to repair habitat damaged by urbanization, off highway vehicle traffic, and invasion by exotic, non-native plants (Arnold 1994).

Mission blue larvae, symbiosis, and ants: Similar to the larvae of other species of butterflies, Mission blue caterpillars participate in a special relationship with particular caretaker ants during the larvae’s spring feeding period. The ants climb onto the backs of the Mission blue caterpillars, stroke the larvae with their antennae, whereupon the larvae secrete a sugary fluid called honeydew, which the ants feed on. In return, the ant helps to protect the larvae from predators and parasites (Arnold 1994).

The Mission blue’s natural enemies: In his study, Six Ecological Studies of Endangered Butterflies, R. A. Arnold (1983) has found that about 35% of field collected eggs were parasitized by an unidentified Encryrtid wasp. Furthermore, tow other parasitic Hymenoptera have been taken from the eggs of various Icarioides races. Rodents are probably the principle predator of both larvae and pupae (Arnold 1983).

Bibliography:

Arnold, R. A. 1983. “Ecological Studies of Six Endangered Butterflies Island Biogeography, Patch dynamics, and design of habitat preserves.” pp. 1-161. University of California Publications in Entomology 99.

Arnold, R. A. 1987. “The Mission Blue Butterfly.” The Audubon Wildlife Report. National Audubon Society, New York.

Arnold, R. A., Hafernik J., Osborne, K. H. 1994. “Mission Blue Butterfly.” Life On the Edge. Santa Cruz, California; BioSystems Analysis, Inc.

Garth, John S. 1986. California Butterflies. Berkeley, University of California Press.

Howe, William H. c1963. Our Butterflies and Moths. North Kansas City, True Color Publication Company.

La Pierre, Yvette. 1998. “On a Mission: The Rare Mission Blue Butterfly
Relies on Habitat Protected by Golden Gate National Recreation Area.” National Parks v72 No. 1/2, January/February, p38.

Powell, Jerry A. 1979. California Insects. Berkeley, University of California Press.

Scott, James A. 1986. The Butterflies of North America: A Natural History and Field Guide. Stanford, California, Stanford University Press.