Delta green ground beetle (Elaphrus viridis)
|Size||Length: 6 mm (2).|
Classified as Critically Endangered (CR B1+2abc+3a) on the IUCN Red List 2004 (1).
This tiny beetle is adorned with an opulent, metallic emerald-green hue, generally with bronze spots and pits on the elytra (3) (4) (5). Its oval shape and green colouration camouflages this diminutive beetle in the small leaves that sprout around its pool habitat, protecting it from hunting birds and amphibians (3).
Now found in just a ten square mile area around Jepson Prairie Reserve in central Solano County, in California’s Central Valley (3) (5).
This beetle has been collected in bare areas along trails and roadsides and around the margins of vernal pools, seasonally wet pools that are dry in the summer and fill with the onset of the winter rains (2) (5). However, while some scientists believe that the species prefers more open habitat, such as edges of pools, trails, roads and ditches, it has also been argued that denser cover elsewhere simply hinders observation of this tiny green beetle (5).
The delta green ground beetle, like many of its neighbours, synchronises its lifecycle with the seasonal changes in its habitat (2) (3). Adults are active in winter and early spring, when pools are wet, laying their eggs between January and April (3). When the pools dry up in the summer, the beetles enter an inactive phase called a diapause, in which they bury themselves underground and await the next rainy season (5) (6). The hatching larvae also burrow into the moist clay for food and shelter and spend the hot summer under the soil (3). The larvae then pupate in autumn and emerge as adults in the cool of winter (2) (3).
Both larvae and adults are active predators, spending most of the day searching out small invertebrates such as midge larvae (Diptera) and springtails (Collembola) (2) (4).
The historical distribution of the delta ground beetle is unknown, but it is thought reasonable to assume that the species was once found throughout the wetlands and grasslands of California’s Central Valley (4). The area has suffered widespread disruption and destruction of its wetland habitat from agricultural development, tapping of vernal pools for irrigation of crops, river channelisation, and encroaching urban development, all of which are thought to have played a role in the demise of this species (2) (4). Additionally, an introduced alien plant, garden lippia (Phyla spp.), poses an immediate threat to the species’ remaining range. The plant forms dense mats in vernal pools, crowding out native vegetation and hindering the beetle’s foraging (2). Only around 75 individuals have been seen since 1974, and the species’ small range places it in very serious danger of extinction (4).
The delta green ground beetle is protected by the Lacey Act, which prohibits its import, export, transport, sale, purchase, receipt or acquisition (4). The beetle is also protected through its occurrence in the Jepson Prairie Reserve (5), but other suitable sites nearby are on private land and negotiations over their protection are ongoing (2). Since its life cycle is intricately intertwined with the seasonal changes of its vernal pool habitat, conservation of the delta green ground beetle very much depends upon the protection of this habitat, which is itself endangered (2). Thus, protection of this disappearing habitat must be the top priority in the conservation of not only the delta ground beetle, but also the array of other endangered species that are unique to and depend heavily upon this threatened vernal pool ecosystem.
For more information on the delta green ground beetle see:
ESSIG Museum of Entomology: California’s Endangered Insects:
Santa Barbara Museum of Natural History: California Beetle Project:
U.S. Fish and Wildlife Service: Sacramento Fish & Wildlife Office Species Account:
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- Elytra: first pair of wings, which in beetles are hardened and act as a protective covering for the flight wings.
- Pupate: the process of forming a pupa, the stage in an insect’s development when huge changes occur that reorganise the larval form into the adult form.
IUCN Red List (August, 2010)