Explanation of Names
"Delta green ground beetle" probably comes from the "delta" shape on the pronotum.
viridis - green.
Bright metallic green, generally with bronze spots on the elytra although some lack the bronze spots. Also, this species lacks or has reduced circular pits on the elytra.
Jepson Prairie Preserve, south of Dixon in Solano County
probably historically occurred through much of California's great Central Valley, though it's actual former native distribution is unknown.
It is presently known to occur only in Solano County northeast of the San Francisco Bay Area.
Around the margins of vernal pools and in bare areas along trails and roadsides.
Found under low-growing vegetation such as filaree (Erodium spp.) 1
The beetle's life cycle is in synchrony with the habitat's; it emerges in January, breeds in February and March, and then enters a period of dormancy in May as the pools dry up.
Both larvae and adults are active predators that seek out small, soft-bodied arthropods such as midge larvae and springtails.
This is a federally threatened species as of August 8, 1980 under the U.S. Endangered Species Act. It is not state listed.
Causes of the Delta Green's decline are fairly clear. The development of the Central Valley for agriculture has eliminated much of the vernal pool habitat, by tilling it for crops, or by tapping the pools for irrigation. In some areas urban and suburban development are encroaching. Poorly managed grazing has brought on the degradation of much of the remaining habitat. Additionally, an introduced plant, garden lippia (Phyla sp.), is an immediate threat. This plant forms dense mats in vernal pool areas crowding out native vegetation and hindering the beetle's foraging.
Conservation of this beetle depends on the protection of the vernal pool habitat which is itself endangered. The beetle's current range includes the Nature Conservancy's Jepson Prairie Preserve, which is largely protected. However, other known sites nearby are on private land and require ongoing negotiations to ensure protection of the habitat. It is also quite possible that populations of this beetle may be found in other parts of the Central Valley.
Arnold, R.A. 1983. Biological studies of the Delta green ground beetle, Elaphrus viridis Horn (Coleoptera: Carabidae) at Jepson Prairie Preserve in 1983. Unpublished report produced for the Nature Conservancy, San Francisco.
Goulet, H. 1983. The genera of Holarctic Elaphrini and species of Elaphrus
Fabricius (Coleoptera:Carabidae): classification, phylogeny and zoogeography. Quaestiones Entomologicae, 19: 219-481
- Essig Museum, UC, Berkely