Elaphrus viridis Horn 1878
Date of listing: 1980
Federal Status: Threatened
State Status: None
The Delta Green Ground Beetle is a small (0.6 cm in length) metallic green carabid beetle which 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.
The Delta Green is associated with vernal pool habitats, seasonally wet pools that accumulate in low areas with poor drainage, which occur throughout the Central Valley. Dry in the summer, these pools fill with the onset of winter rains. 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.
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.
For further reading:
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 Unpublished report produced for the Nature Conservancy, San Francisco.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., 1982. Genera of holarctic Elaphrini and species of Elaphrus (Fabricius) (Coleoptera: Carabidae): Classification, phylogeny, and zoogeography. Quaestiones Entomologicae 19: 219-482.