Mount Hermon June Beetle
Mount Hermon June Beetle
|Listed||January 24, 1997|
|Family||Scarabaeidae (Scarab beetle)|
|Description||Small scarab beetle with a black head; dark blackish brown, thick, leathery forewings clothed with scattered long brown hair; and a striped body.|
|Habitat||Ponderosa pine-chaparral with sandy soil and open, sparsely vegetated areas.|
|Food||Roots of monkeyflower, oak, fern, grass, and pine.|
|Reproduction||Females lay eggs at the bottom of their burrows and die soon after.|
|Threats||Destruction of habitat from sand mining and urban development; predation by birds.|
The Mount Hermon June beetle was first described in 1938, with the name coming from the place it was discovered in Santa Cruz County, California. The adult male is a cryptic small scarab beetle with a black head, dark blackish-brown elytra (thick leathery forewings) clothed with scattered long brown hair, and a striped body. Elytral vittae (stripes) are broken, often reduced to discontinuous clumps of scales, but still form identifiable lines. Females are larger, with a black head, chestnut-colored clypeus (plate on lower part of face) and elytra, and golden hairs on the head, thorax, and legs. The single adult female described was 0.87 by 0.43 in (2.2 by 1.1 cm), while the holotype male was 0.79 by 0.39 in (2 by 1 cm).
The Mount Hermon June beetle is one of 28 species of Polyphylla in North America north of Mexico, and one of 15 species of the diffracta complex within the genus Polyphylla. The status of P. barbata as a full species was supported in 1940 and again in 1988; several nomenclatural adjustments were made to the genus Polyphylla in the late twentieth century but P. barbata was retained. Other wide-ranging species of Polyphylla that occur in the Ben Lomond-Mount Hermon-Scotts Valley area are P. crinita, P. nigra, and P. decemlineata. The Mount Hermon June beetle is distinguished from other species of Polyphylla by the presence of relatively dense, long, erect hairs scattered randomly over the elytra and short erect hairs on the pygidium (abdominal segment).
Like other Polyphylla species, the Mount Hermon June beetle is believed to require about two to three years to mature from an egg through the adult form. The rate of growth of laboratory-reared larvae, however, suggests that the Mount Hermon June beetle may complete its life cycle within one year. Most of the life cycle is spent in larval stages. The larvae are subterranean and feed on plant roots. While Polyphylla larvae are generally considered to be grass and pine root feeders, the Mount Hermon June beetle also may feed on the roots of monkeyflower, oak, fern, and other plants found in the Zayante sand hills ecosystem.
Mount Hermon June beetles emerge during summer as imagos (adult forms) to reproduce. Males are strong fliers, emerging from their burrows to fly low to the ground in search of females. Females are thought to be fossorial, remaining just below the surface in burrows, as they cannot fly due to their large body size. Like other Polyphylla species, males are believed to locate females by tracking female pheromone signals; such a mechanism would ensure reproductive success within the limited period for mating. The flight season generally extends from mid-June to late July. The flight time of males appears restricted to evening, being observed only between 8:45 and 9:30 P. M.; flights may occur later during the later part of the flight season.
The small mouthparts and limited flight period of Mount Hermon June beetles suggest that adults of this species do not feed. Adults of the related P. decemlineata are known to feed on the leaves of trees. At the end of the flight period each evening, males burrow back into the soil, emerging repeatedly on subsequent evenings to search for mates until their nutrient reserves expire. Females are believed to lay eggs at the bottom of their burrows and die a short time later. The life cycle continues as newly hatched larvae tunnel from the burrow in search of roots.
Habitat of the Mount Hermon June beetle is described as ponderosa pine-chaparral with sandy soil and open, sparsely vegetated areas. Mount Hermon June beetles also may occur in more vegetated areas of chaparral. Common vegetation found in these open areas includes bracken fern (Pteridium aquilinum ), monkeyflower (Diplacus sp.; Mimulus sp.), grasses, and small annual forbs. While not always present, silver-leafed manzanita seems to be a good indicator of suitable habitat. All of these descriptions are consistent with those of Zayante sand hills habitat.
Most Polyphylla species have narrow distributions. Of 28 North American species, 20 have restricted ranges; 15 of these are endemic to isolated sand deposits. The restricted distributions of these species are likely due to various factors including substrate and food preferences, edaphic tolerances, and the low mobility of fossorial larvae and females. Most Polyphylla species seem to prefer sand and grass or sand, grass, and conifer associations similar to those found in the Zayante sand hills ecosystem.
The range of the Mount Hermon June beetle is restricted to the Zayante sand hills habitat of the Ben Lomond-Mount Hermon-Scotts Valley area. Specimens were known historically only from sand hills at the type locality of Mount Hermon in Santa Cruz County, California. A single historic specimen collected in 1968 and labeled only "Santa Cruz" has been reported. This is not helpful in extending the historic range of the beetle because of its nonspecific location label.
Between 1989 and 1994, Mount Hermon June beetles were collected at 28 of 43 sites surveyed. Records include results of a regional survey and incidental collections. Twenty-six of the 28 collection locations were on mapped Zayante soils in the primary cluster of the Ben Lomond-Mount Hermon-Scotts Valley area. The other two collection records were within the same area, in proximity to mapped Zayante soils. All sites were similarly characterized by sparsely vegetated sandy substrate with silver-leafed manzanita or ponderosa pine. Mount Hermon June beetles were not found either in surveys of suitable Zayante sand hills habitat outside the Ben Lomond-Mount Hermon-Scotts Valley area nor at locations with habitat uncharacteristic of the Zayante sand hills ecosystem.
The Mount Hermon June beetle is primarily threatened by habitat destruction in the Ben Lomond-Mount Hermon-Scotts Valley area through sand mining and urban development. Excavation and construction activities that crush or expose fossorial larvae and females result in individual mortalities and the elimination of reproductive populations. The clearing of native Zayante sand hills vegetation and the cultivating of non-native plant species in landscaping also may adversely affect the Mount Hermon June beetle by eliminating food plants and disrupting the soil. Lesser sources of habitat loss and alteration are recreational activities and agriculture.
Sand mining and urban development have been the agents for most of the more than 40% of historic Zayante sand hills habitat lost or altered. This habitat once covered an estimated 6,265 acres (2,535 hectares); now only 3,608 acres (1,460 hectares) remain in a natural state. Portions of the Zayante sand hills ecosystem are protected under public ownership only at the Quail Hollow Ranch, owned by the County of Santa Cruz; Bonny Doon Ecological Preserve, managed by the California Department of Fish and Game; and Henry Cowell Redwoods State Park. The Mount Hermon June beetle, however, is not known to occur in either the Bonny Doon Ecological Preserve or Henry Cowell Redwoods State Park. The majority of Zayante sand hills habitat is on privately owned properties—no federal land is located in the region—and is susceptible to continued sand mining and urban development. Seventeen of the 28 Mount Hermon June beetle collection locations are adjacent to areas used for sand mining. Recent expansion of juvenile hall facilities near Mount Hermon eliminated portions of an area known to support Mount Hermon June beetles. Fourteen collection sites for Mount Hermon June beetles are adjacent to residential, commercial, and public developments.
Amateur collecting for the Mount Hermon June beetle occurs on a limited basis during the narrow flight periods of the species; th interest of collectors, however, may increase as these insects become even more difficult to find.
Mount Hermon June beetles may be preyed upon by some bird species, although the early evening flight time of this insect is thought to reflect an evolutionary adaptation for predator avoidance, coinciding with the cessation of bird activity. Based upon laboratory observations, larvae may be susceptible to fungal infestations if soil conditions are too moist. The significance of these mortality sources is unknown.
Because the Mount Hermon June beetle is fossorial, airborne pesticides would not likely reach and affect the species, but the application of soil permeant pesticides could pose a threat. During the flight season males of this species also may be subject to mortality from attraction to electric "bug zappers." The significance of such mortality is unknown, however.
Conservation and Recovery
The 28 known sites have been secured through fee-title acquisition, conservation easements, or habitat conservation plans for the Granite Rock Quarry, Kaiser Sand and Gravel's Felton Plant, the County of Santa Cruz, and the City of Scotts Valley. A management plan for Quail Hollow County Park has been developed and is being implemented, and the population numbers are stable or increasing.
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
U. S. Fish and Wildlife Service. 1998. "Recovery Plan for Insect and Plant Taxa from the Santa Cruz Mountains in California." U. S. Fish and Wildlife Service, Portland, Oregon. 83 pp.