Quino Checkerspot Butterfly

Euphydryas editha quino

Description

The quino checkerspot, Euphydryas (=Occidryas) editha quino, is a small member of the brush-footed butterfly family Nymphalidae. It has about a 1 in (2.5 cm) wingspan and is checkered with dark brown, reddish, and yellowish spots. It is one of 12 recognized subspecies of E. editha (editha checkerspot). The quino checkerspot can be distinguished from other subspecies of E. editha in that the quino check-erspot tends to be larger with redder wings, and the light spots on the wings tend to be fewer and more discrete. This taxon also looks similar to two other species of butterfly that occur within its range. The Chalcedon checkerspot (E. chalcedona ) is yellower and slightly larger, with sharper forewings, than the quino checkerspot. Gabb's checkerspot (Chlosyne gabbii ) is smaller than the quino checkerspot and has orange rather than red markings.

Adult quino checkerspot butterflies live from four to eight weeks. The flight season occurs from mid-January to late April and peaks between March and April. The eggs hatch in about 10 days and the larvae begin to feed immediately. Fourth instar (development stage) larvae enter an obligatory diapause as summer approaches and their larval food plant dries up. Extended periods of dia-pause may occur during times of drought. Post-diapause larvae develop through four more instars and then pupate to emerge as adults in the early spring.

Behavior

The primary larval food of the quino checkerspot is dwarf plantain (Plantago erecta ). Secondary foods are P. ovata and Castilleja exserta. The butterfly often basks in the winter sun.

Habitat

The quino checkerspot is restricted to open grassland and sunny openings within chaparral and coastal sage shrubland habitats of the interior foothills of southwestern California and northwestern Baja California, Mexico. Like the Laguna Mountains skipper, its distribution is defined primarily by that of its larval host plants. These plants grow in or near meadows, vernal pools, and lake margins, and spread to upland shrub communities of sparse chaparral and coastal sage scrub. This butterfly is generally found at sites where high densities of the host plants occur and at a variety of elevations from about sea level to about 3,000 ft (914 m). Within these areas, the quino checkerspot may be preferentially selecting sites where exposure to winter sun is greatest. These habitats, like the quino check-erspot, were once common along coastal bluffs, mesas, and inland foothills.

Distribution

The quino checkerspot may have been one of the most abundant butterflies in San Diego, Orange, and western Riverside counties during the early part of the twentieth century. The original range of the quino checkerspot extended as far south as Valle de la Trinidad in northwestern Baja California, Mexico and as far north as Point Dume in Los Angeles County. Currently, only seven or eight populations are known within the United States (the lack of an exact count is due to uncertainty as to whether sightings of very small numbers of butterflies in two areas represent one or two populations). All known extant populations in the United States occur in southwestern Riverside and north-central San Diego counties. One population near Upper Otay Lake in San Diego County was last seen in 1990. In 1996, a very small group of quino checkerspots was sighted on Otay Mesa, but because of the very limited amount of available host plant, this occurrence was not expected to persist beyond 1996. At least one population exists in Mexico, in the Sierra Juarez near Tecate. Although no estimates of population sizes for the quino checkerspot are currently available, all but three populations are known to comprise fewer than five individuals.

Threats

Fifty to 75% of the known range of the quino checkerspot has been lost since 1900 due to habitat degradation or destruction. Sunny openings within chaparral and coastal sage scrub occupied by the quino checkerspot have been degraded by grazing and, to a lesser degree, destroyed by urban development. The primary larval food plant, Plantago erecta, can be displaced by exotic plants that invade once the ground is disturbed by discing, grading, and/or grazing. The host plant then recolonizes in sites where grasses do not grow well, like cattle trails and road edges, where quino checkerspot larvae are subject to trampling. The encroachment of urban development in rural Riverside County potentially threatens two of the largest populations of quino checkerspot. This area is growing rapidly and is projected to be fully developed within the decade. One population is in an area that is included in a local community plan that provides for subdivision of parcels into 20-acre (8.1-hectare) lots. Another population is on the site of an approved preliminary map for a housing development. The loss of these two populations is likely to preclude survival and recovery of the taxon.

The quino checkerspot population in southern San Diego County may be threatened by a proposed urban development project on Otay Mesa. The preferred alternative for the Otay Ranch New Town Plan (the largest planned community in the southwestern U. S.) would result in the loss of 14,000 acres (5,665 hectares) of upland shrub communities, or about 52% of the extent of the plant communities within the project area. The effects of this project on the recently observed quino checkerspot population on Otay Mesa are not known at this time but are likely to be significant.

Additional development is expected to further reduce and degrade habitat of the quino check-erspot through construction of homes and roads, and increases in fire frequencies, unauthorized trash dumping, and the distribution and abundance of exotic plants. An existing recreational vehicle park and marina in the vicinity of quino checkerspot habitat attracts unauthorized use of off-road vehicles within natural habitat areas. Off-road vehicles increase erosion and fire hazards and destroy habitat by creating trails. Evidence of off-road vehicle use is apparent at one of the quino checkerspot localities, where a recently created dirt road bisects the center of the habitat. Quino checkerspot habitat at this locality has also been disced in part; these disturbed areas no longer support this taxon, while the surrounding undisturbed areas do.

There is evidence that predation is a threat to the quino checkerspot. Preliminary studies indicate that predation has contributed to the decline of the quino checkerspot at sites where habitat has been invaded by non-native plant species, which may also harbor predatory arthropods. Sites within historical quino checkerspot habitat that have been heavily invaded by Mediterranean plant species also have high sowbug (Armadillidium sp. and Porcellio sp.) and earwig (Euborellia annulipes and Forficula auricularia ) densities. Sowbugs and earwigs prey upon butterfly eggs. These predators are absent from natural sites currently occupied by the quino checkerspot. Argentine ants are also a potential predator that co-occur with earwigs and sowbugs. The number of these introduced predators is expected to increase with the spread of development because these exotics thrive in irrigated horticultural environments which may be adjacent to natural quino checkerspot habitat.

The quino checkerspot is somewhat adapted to unpredictable weather patterns but requires sufficient patches of suitable habitat to respond to this environmental variability. The quino checkerspot's dispersal capabilities vary considerably depending upon rainfall patterns and the resulting availability of adult nectar sources and larval food plants. For example, in 1984 a San Diego County population of the quino checkerspot exhibited an increase in numbers as a result of favorable weather. The greater number of larvae defoliated the larval food plants. This central core area was left without sufficient egg-laying sites for females, and adults dispersed greater distances in search of additional suitable habitat. Ideally these dispersing adults would have found marginally suitable areas and, in subsequent generations, would have returned to a central core area. In this case, the mass dispersal failed to restore populations in previously occupied habitat, and the butterflies have not recolonized the original site.

Conservation and Recovery

No specific regulations protect the quino check-erspot in Mexico. However, all hunting and export of wildlife in Mexico is prohibited, except under permit. Little is known of the status of the isolated populations in Mexico and any protection afforded to these populations does not insure the survival of the taxon.

The quino checkerspot may be provided some protection to one population by its occurrence, in part, on Bureau of Land Management land in Riverside County. However, this Federal land is currently subject to off-road vehicle activity.

Contacts

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Complex
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
Telephone: (503) 231-6121
http://pacific.fws.gov/

U. S. Fish and Wildlife Service
Carlsbad Field Office
2730 Loker Avenue West
Carlsbad, California, 92008-6603
Telephone: (760) 431-9440
Fax: (760) 431-9624

Reference

U. S. Fish and Wildlife Service. 16 January 1997. "Endangered and Threatened Wildlife and Plants: Determination of Endangered Status for the Laguna Mountains Skipper and Quino Checkerspot Butterfly." Federal Register 62 (11): 2313-2322.