PROCEEDINGS San Diego Society of Natural History
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The Scarabaeoid Beetles of San Diego County, California PROCEEDINGS of the San Diego Society of Natural History Founded 874 Number 40 February 2008 The Scarabaeoid Beetles of San Diego County, California Part I. Introduction and Diagnosis of Families Glaresidae, Trogidae, Pleocomidae, Geotrupidae, Ochodaeidae, Hybosoridae, and Glaphyridae Ron H. McPeak P.O. Box 2136, Battle Ground, WA 98604, U.S.A.; rmcpeak@worldaccessnet.com Thomas A. Oberbauer County of San Diego Department of Planning and Land Use, 5201 Ruffin Road, Suite B, San Diego, CA 92123, U.S.A.; thomas.oberbauer@sdcounty.ca.gov ABSTRACT.—Scarabaeoid beetles are diverse in San Diego County, California, with 8 families, 53 genera, and approximately 50 species repre- sented. Vegetation communities in the county are likewise diverse and directly responsible for supporting the diversity of scarab beetles. Part I of the Scarabaeoid Beetles of San Diego County, California presents data on 8 species in the following 7 families: Glaresidae (), Trogidae (4), Pleocomidae (2), Geotrupidae (5), Ochodaeidae (3), Hybosoridae (), and Glaphyridae (2). This group of diverse beetles is adapted to a wide variety of terrestrial habitats where they feed upon hair, feathers, carrion, other decomposing organic matter, and plants. INTRODUCTION COLLECTING IN SAN DIEGO COUNTY The superfamily Scarabaeoidea is one of the largest groups of Several preeminent beetle taxonomists spent time collecting beetles, containing approximately 2200 genera and 3,000 species in San Diego County during the 9th century (Essig 93). John worldwide (Jameson and Ratcliffe 2002). According to Smith (2003) L. LeConte was in California during 850 while employed as a there are 2 families, approximately 70 genera, and 2000 species in surgeon in the U. S. Army and collected in San Diego County and the United States, Canada, and nearctic Mexico. This diverse group other parts of the state. George H. Horn was active in the California is adapted to a wide variety of terrestrial habitats on all continents Volunteers during the Civil War from February 863 to April 865 except Antarctica and eats a variety of materials, including fungi, and spent time collecting Coleoptera at Warner Springs during his plants, carrion, hair, feathers, dung, or other decomposing organic service. Frank E. Blaisdell moved to San Diego in 87 and then to a materials. A few species are predators on other insects. Scarabaeoid ranch near Poway in 875. Blaisdell collected throughout the county beetles, or scarabs, are characterized by having platelike antennal and amassed a huge collection of beetles, including many scarabs. segments, or lamellae. Their robust bodies often have powerful legs His collection of 200,000 specimens now resides at the California adapted for burrowing in rotten wood or soil. Scarabs are usually Academy of Sciences, San Francisco. black, brown, yellowish brown, reddish brown, or green. A few Oliver N. Sanford moved from Massachusetts to San Diego species are metallic or scaled with blotched or striped patterns. The in 872 and collected beetles throughout the region for nearly 30 larvae or grubs are whitish and C-shaped with a distinct head and years. He sent specimens to LeConte, Horn, and others and sold well-developed legs. his collection to Blaisdell in 89. George H. Field, a long-time Scarabaeoid beetles are abundant in San Diego County, with 8 collector, moved to San Diego County in 889 and collected in families, 53 genera, and approximately 50 species represented. Part many remote areas of San Diego and Imperial counties and Baja I of this series covers 8 of the county’s species in the following 7 California, Mexico. He furnished much of his material to Henry C. families: Glaresidae (), Trogidae (4), Pleocomidae (2), Geotrupidae Fall, Edwin C. Van Dyke, and Blaisdell. Thomas L. Casey collected (5), Ochodaeidae (3), Hybosoridae (), and Glaphyridae (2). The in California from San Diego to Eureka in 885 and 886. Though family Scarabaeidae, which accounts for approximately 30 of 50, Casey described many species of scarabs from California many of or 87% of the scarab beetle species in San Diego County, will be his names proved to be synonyms of species described previously treated in subsequent parts of this series. Part II will cover the sub- by LeConte, Horn, and others. families Aphodiinae and Scarabaeinae, part III the Melolonthinae, The first modern listing of beetles in San Diego County was com- and part IV the Dynastinae, Rutelinae, and Cetoniinae. piled by Ian Moore (937). The list included 8 species of scarabs 2 Ron H. McPeak and Thomas A. Oberbauer and was based largely on the collections of Blaisdell and Field. A. very dry hot lowlands of the western reaches of the Colorado Desert. R. Hardy, A. V. Evans, D. K. Faulkner, J. W. Brown, S. E. Haskins, Sand dunes resulting from windblown sediments occur in the eastern and R. L. Parks collected in the county at various times from the portion of the desert region. San Diego County contains roughly 44 960s through the 990s. These entomologists were responsible hectares of active dunes and 380 hectares of stabilized dunes, as well for collecting much of the material from San Diego County now as alkali flats in the beds of the Borrego Sink and Clark Dry Lake. in museums. McPeak began collecting scarab beetles in the county San Diego County has a varied climate. The majority of the in 966 and through August 2007 spent nearly 500 days (and/or precipitation falls as rain during the winter months (December nights) collecting throughout the county. The extensive collecting through March) with the exception of some summer thunderstorms in the county since 937 has yielded numerous additional species, (July through September) and winter snow in the mountains. There raising the county’s total to approximately 50 species of scarabaeoid is great variation in rainfall from year to year. For instance, rainfall beetles as of 2007. measured at Lindbergh Field (season July–30 June) ranged from 76.5 mm in 200–2002 to 57.3 mm in 2004–2005. In 200–2002 SAN DIEGO COUNTY GEOGRAPHY AND CLIMATE precipitation was the lowest recorded since at least 85 (Unitt 2004), while rainfall in 2004–2005 was the third highest since 883–884. San Diego County covers roughly .093 million hectares and is Typical annual precipitation ranges from 20 to 300 mm along the located in the southwest corner of California. It is bordered on the coast, 260 to 400 mm in the coastal valleys and 500 to 1100 mm in north by Riverside and Orange counties, on the east by Imperial the mountains. The desert regions receive only 70 to 30 mm per year County, and on the south by the international border with Baja Cali- with half of that falling during summer thunderstorms (Rand Allan, fornia, Mexico (Figs. , 2). The Pacific Ocean lies to the west. County of San Diego, Department of Public Works, 2005). The county straddles the Peninsular Ranges geologic province Along the coast temperatures are relatively mild and fluctuate of southern California, which consists of a series of coastal mesas, within a rather narrow range, averaging about 7o C in winter (December foothills and intervening valleys, and mountains up to 99 meters through March) and 26o C in summer (July through September). Tem- in elevation. The Peninsular Ranges include the Santa Margarita, peratures are more extreme in the inland valleys of the coastal lowland Volcan, Cuyamaca, Agua Tibia, Palomar, and Laguna mountains. and foothill zone where frost may occur during the winter and summer To the east of these mountains a steep escarpment drops down to the highs average 3–34o C. The mountain zone is the coolest region of the Figure . Principal localities named in San Diego County. The Scarabaeoid Beetles of San Diego County, California 3 Figure 2. San Diego County topography. county. During the winter temperatures average –2–0 o C, in the sum- beetles common in urban/agricultural areas include Aphodius Illiger, mer high temperatures average 29–3o C. In the desert summer heat is Parathyce Hardy, Serica MacLeay, Cotinis Burmeister, and Tomarus extreme, with average highs of 4–46o C and a maximum of 50.6o C Erichson (all of family Scarabaeidae). (National Weather Service website, San Diego Office, 2005). Coastal Dunes SAN DIEGO COUNTY VEGETATION COMMUNITIES Coastal dune habitat (sometimes referred to as coastal strand), Vegetation communities (Fig. 3) in San Diego County are di- mostly disturbed by human activity and development, is now limited verse and directly responsible for supporting the county’s diversity to a few locations, as on the southern Silver Strand, in Torrey Pines of scarab beetles. Vegetation patterns are correlated with climatic State Reserve, and at the mouth of Santa Margarita River. Camissonia and geological conditions, including soil type, exposure, and level cheiranthifolia (Sprengel) Raim (beach evening primrose), Ambrosia of precipitation. We discuss beetle distribution with respect to these chamissonis (Less.) E. Greene (beach-bur), Astragalus spp., and vegetation communities where an association is important, especially Cakile maritima Scop. (sea rocket) grow in this community. Typical for phytophagous species. The nomenclature for plants follows Hick- genera of scarab beetles in this vegetation are Aegialia Latreille, man (993). Tesarius Rakovic, and Aphodius (all of family Scarabaeidae). Urban/Agricultural Coastal Sage Scrub Modern development and agriculture in San Diego County, Much of the coastal sage scrub that formerly covered much of especially in coastal and mesa areas west of the mountains, have coastal San Diego County has been lost to urban development. The eradicated extensive areas of native vegetation. Coastal sage scrub, remains of this community are dominated by Artemisia californica coastal dunes, and chaparral have been especially affected. Non-na- Less. (California sagebrush), Eriogonum fasciculatum Benth. (Cali- tive plant species have been introduced widely.