Macrohabitat: Lowlands, 20 – 34 meters altitude, at margins of vernal pools.
Microhabitat: Adults are ground-dwelling on moist, clayish-muddy substrate, among Juncus
plants. Dispersal abilities: Macropterous, probably capable of flight; swift runners. Seasonal
occurrence: Adults have been found in February and May. Behavior: Diurnal; active
in the sunshine.
Distribution: Native, New World. USA – CA.
Common names: Delta Green Ground Beetle
Delta Green Marsh and Bog beetle
Synonyms: Elaphrus viridis G. Horn, 1878:52
Elaphrus horni Csiki, 1927:420
Regularity: Regularly occurring
Type of Residency: Year-round
Global Range: (<100 square km (less than about 40 square miles)) Only known from the greater Jepsen Prairie area in south-central Solano County, California. The historical distribution is unknown, but data suggests that it may have inhabited a much larger range than it does presently (USFWS, 2005). It presently occupies less than 2,800 hectares (7,000 acres) (USFWS, 2007; USFWS, 2005).
Length: 0.55 cm
Habitat and Ecology
Comments: Found along the margins of vernal pools within 1.5 meters of the water. Specifically the microhabitat seems to consist of areas where the sandy mud substrate slopes gently into the water, and where there is very low-growing vegetation providing 25-100% cover. Beetles have however been found hundreds of meters from vernal pools (Arnold, 1983).
Non-Migrant: No. All populations of this species make significant seasonal migrations.
Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).
Locally Migrant: No. No populations of this species make annual migrations of over 200 km.
Comments: These predators consume soft-bodied prey, with springtails forming the bulk of their diet. One type of springtail in particular, a light tan- colored one which jumps readily when approached, is chased whenever it is noticed, but only captured about 14% of the time. (For comparison, in NOTIOPHILUS 60% of the springtail catching attempts were successful, whereas there was a maximum of 4% success in four other species of carabid beetles (Thiele, 1977).) The tan-colored springtail is a numerous prey item with about one visible moving adult springtail every eight by eight cm piece of substrate. Smaller springtail instars are difficult for an observer to see in the field but are still prey items (Serpa, 1985).
A dark grey springtail, which does not hop, was not eaten even when ELAPHRUS touched them with their mouthparts. The same is true for an abundant red mite. Although one adult midge was eaten, most were also ignored even after contact. Beetle larvae were chased, but usually escaped before physical contact. One two mm larva was seen being eaten, and a larger larva about the length of an adult ELAPHRUS was abandoned after the beetle grabbed it in its mandibles. In this case the beetle immediately began cleaning itself and continued to do so for over twenty minutes. It was probably the victim of a defensive secretion released by the larva. They chased several other species of beetles, but only managed to make contact with a weevil which was not eaten (Serpa, 1985).
HUNTING METHODS: Open area hunting, feeding arenas, and cavity hunting are the three main methods.
In open area hunting, the beetles wander over the sandy areas in between vegetation patches and chase any prey items they see moving across the substrate. A chase is initiated when a beetle is about one cm or less away from a prey item. This technique is not very successful.
Feeding arenas are much more productive. The one-half to one cm high vegetation in the preferred habitat is not uniform and includes innumerable openings, often circular and about one to two beetle-lengths in diameter. The vegetative uprights poking through the sand are often fairly cylindrical and resemble a miniature picket fence enclosing a small area of bare sand. A beetle enters one of these "arenas" and faces toward the vegetation/substrate interface. After a few seconds it rotates within the ring and looks in another direction. This procedure is repeated many times before in the same arena. The beetle is relatively inconspicuous due to its immobility, thus the springtails can easily wander from beneath the vegetation into the arenas without noticing the beetle. When a beetle sees a springtail it rushes forward and attacks. The advantage of the feeding arena is that when a springtail hops it often hits the plant uprights that form the "picket fence" and falls right back down where the beetle can capture it.
In cavity hunting the beetles enter vertical holes in the sandy mud about 1 cm or less in diameter. They go into the holes head first, usually with the tips of their elytra still protruding, and emerge a few seconds later. These cavities probably act as natural springtail pitfall traps (Serpa, 1985).
Number of Occurrences
Note: For many non-migratory species, occurrences are roughly equivalent to populations.
Estimated Number of Occurrences: 1 - 5
Comments: There are currently six occurrences of this beetle in California, five are extant and one is extirpated (California Natural Diversity Database, accessed May 2009).
Comments: There have been no coordinated systematic annual surveys or population monitoring of the delta green ground beetle to determine population and demographic trends (USFWS, 2005). Statistical estimates of population sizes were not possible to determine in a 2007 range wide survey (Arnold and Kavanaugh, 2007) due to the limited number of individual beetles found at any one location. Therefore population size remains unknown due to the difficulty in surveying for this cryptic beetle, its little-known biology and ecology, and other abiotic and biotic factors (USFWS 2009).
The original description occurred in 1878 from a single specimen, and the only locality data indicated that it had come from California (Horn, 1878). The actual habitat remained unknown until it was rediscovered by a U.C. Davis student in 1974. Between that date and Arnold's report (1983), 76 beetles were seen. Between February 8, 1985, and April 11, 1985, 133 Delta green ground beetles (94 spotted morph, 39 solid) were sighted. Some of these may have been the same beetles seen at different times. However, it is clear that this number represents only a portion of the total beetle population. In 1985, extensive field work focusing on individual specimens, in order to learn as much as possible about the species life history, was conducted. Many individual beetles were followed for half-hour periods after discovery, which reduced the number of beetles that could be seen on any given day. On March 13, 1985, without repeating locations, 38 (30 spotted, 8 solid) beetles were observed. Of these, 33 (27 spotted, 6 solid) of them were seen during a 2- hour-and-24-minute period at one location. The greater number of spotted versus solid morphs observed could have been an artifact resulting from the apparent greater activity of the spotted forms. The spotted morphs tend to move around more and so are more noticeable (Serpa, 1985).
PREDATION: No successful attacks by predators were observed. Golden-haired dung flies (SCATOPHAGA STERCORARIA) would rotate toward the beetles that moved close to them. On nine occasions the flies were seen to attack, but the beetles were released within a second or two of contact. Evidently the beetles are so inedible that the dung flies eventually learn not to attack them, particularly if the beetles are numerous and the flies have several unsuccessful encounters in a short period of time.
A saldid bug and a crab spider also released beetles right after they attacked them. The beetles did not seem injured and often continued walking as though nothing had happened. Only one of the 133 beetles observed appeared injured. It had pieces torn from the distal margin of the elytra and was trailing a damaged membranous wing behind its body (Serpa, 1985).
Shorebirds are probably not significant predators. This is because these extremely cryptic beetles freeze when they see large objects move, making themselves almost invisible. In addition, stridulation may serve as a warning to potential bird predators of this beetle's pygidial defense secretions. A weak scratching sound can be heard from beetles held right up to the ear. Other ELAPHRUS spp. are known to stridulate, which serves as a warning and often causes birds to release their prey. If the birds persist these ELAPHRUS species release their pygidial defense secretions 20% of the time (Thiele, 1977).
Pacific treefrogs (HYLA REGILLA) could be the most serious predator. Although no predation events have been actually observed, these highly camouflaged frogs are found along the pool margins and are known to be ambush predators.
Life History and Behavior
Comments: Most sightings have been between February and May, but some have been occurred as early as late fall (Arnold, 1985). These diurnal beetles are most active on sunny, nonwindy (zero-eight mph) days when the temperature is 62-70 F. They become active after sunrise, when the temperature has risen to 64 F. The earliest sighting occurred at 7:40 a.m. on April 3, 1985. They continue moving around until after sunset, becoming immobile only when it becomes so dark that they are difficult to see from 8 cm away. This occurred at 6:00 p.m. (51 F) on February 13, 1985 (Serpa, 1985).
At temperatures higher than 62-70 F these beetles become less mobile and spend more time underneath vegetation obscured from view. On wind more time is spent underneath vegetation. This may be connected to the observation that, when the gusts exceed 20 mph, the beetles in the open can lose their hold and be blown across the substrate until they right themselves or gain shelter in the vegetation.
Six copulations were observed in the field between February 13, 1985, and March 13, 1985. Three of these matings involved a single female which copulated with one male once and another male twice during a 30-minute period. Males actively search through the vegetation for females who hide in the plant cover or run away from the males. Males chase the females when they see one moving nearby, and mounting occurs almost immediately upon contact. Copulations lasted from 42 sec to 2 min and 56 sec, with an average duration of 1 min and 43 sec. When mounted, the spotted male would occasionally move his antennae back and forth, but the pair remained largely motionless. The copulation is terminated when the female tries to either shake the male off or move away from him. The male then chases the female until she manages to elude him in the vegetation.
In all cases in which copulation was observed, the beetle on the top (male) was spotted and the one on the bottom (female) was solid green. Nine encounters between two spotted beetles were observed. They separated immediately after contact, or after a brief one to two second mounting (Serpa, 1985). These observations imply that the solid green beetles are females and the spotted ones are males. However, according to Dr. Kavanaugh (1985) this sexual dimorphism does not hold for the California Academy of Science's collection of E. VIRIDIS specimens.
Gravid females that Kavanaugh (1985) has obtained from the field in February and March have laid two to four eggs. Kavanaugh has reared first and second instar larvae from eggs obtained in this way.
IUCN Red List Assessment
Red List Category
Red List Criteria
- Needs updating
- 1994Vulnerable (V)
- 1990Vulnerable (V)
- 1988Vulnerable (V)
- 1986Vulnerable (V)
- 1983Vulnerable (V)
National NatureServe Conservation Status
Rounded National Status Rank: N1 - Critically Imperiled
NatureServe Conservation Status
Rounded Global Status Rank: G1 - Critically Imperiled
Reasons: This beetle is only known from the greater Jepson Prairie area in south-central Solano County, California. It presently occupies less than 2,800 hectares (7,000 acres). It has a highly restricted range which is threatened by agricultural practices in the area.
Date Listed: 08/08/1980
Lead Region: California/Nevada Region (Region 8)
Where Listed: Entire
Population location: Entire
Listing status: T
For most current information and documents related to the conservation status and management of Elaphrus viridis , see its USFWS Species Profile
Degree of Threat: A : Very threatened throughout its range communities directly exploited or their composition and structure irreversibly threatened by man-made forces, including exotic species
Comments: AGRICULTURE: The primary threat is the conversion of the grassland vernal pool matrix to agriculture and the subsequent plowing that accompanies this conversion. This represents a permanent loss of habitat. Much of the original habitat has already been destroyed in this manner. SUBDIVISIONS: Expansion of housing subdivisions existing near actual and/or potential sites would mean permanent loss of habitat. GRAZING: Cattle, sheep and horse grazing is less destructive than conversion to agriculture or subdivisions because it is reversible. Of these, cattle present the greatest threat because they are so heavy that their feet sink into the soft wet mud, creating a pock-marked topography that is difficult for the beetles to negotiate. This damage is compounded because cattle spend a lot of time near or even in vernal pools. The shoreline of cattle grazed pools is also altered, the gentle slopes that ELAPHRUS prefers being replaced by relatively steep 15-30 cm high banks around the vernal pools. Finally, the shoreline often develops an ammonia smell which might explain the lack of vegetation and springtails along the shores of cattle grazed pools. Sheep grazing is less detrimental, but when concentrated it can also pollute a vernal pool to the point where it is only poor habitat. Since sheep weigh less than cattle, they are less likely to cause negative land form effects. However, in areas where there is soft mud instead of the firmer sandy mud, even the weight of sheep is enough to pock-mark the pool margin with hoofprints. At present only a few horses are in the area of actual and potential habitat, but horses are almost as bad as cattle. HUMAN DISTURBANCE: This problem comes from Coleoptera collectors. It was no accident that the locality for the species was unknown from 1878 until 1974, as the original collector probably did not want other beetle collectors to know where to find the species. Collectors pose a potentially serious threat. The precise locations in which this species is found should not be revealed to the general public or even educational institutions.
Restoration Potential: The recovery potential of this area is excellent. With the elimination of grazing, or at least the cessation of cattle grazing and reduction in sheep numbers, almost all of the vernal pools examined would become excellent quality habitat within a few years.
Preserve Selection and Design Considerations: It would be best if the entire remaining grassland vernal pool region between Jepson Prairie and Travis Air Force Base was protected from agriculture and subdivision. It is not known how large an area the beetles actually inhabit, or how extensive the natural lands must be to retain the unique hydrology responsible for the perpetuation of the vernal pool grassland habitat. At a minimum, the roughly five-square-mile area that was searched for the beetle in 1985 should be preserved in its natural state.
Flight could make dispersal away from small protected sites a strong possibility. The only way to insure the species remains extant is to protect a large enough portion of the grassland vernal pool ecosystem so that the beetles can move around without detrimental effects to their population. Purchase of the above region and the elimination of grazing is the best plan. Barring this, conservation easements should be acquired for this area restricting use to light sheep grazing. Cattle and horse grazing should not be allowed.
Management Requirements: Habitat maintenance might be required to keep the vegetation from becoming too dense, through either limited grazing by sheep or prescribed burning. If grazing occurs on a site, pollution of the vernal pools must be controlled by fencing.
At the present time the entire grassland vernal pool ecosystem in the area, except for one site, is grazed by cattle, sheep or horses.
Management Research Needs: The following questions need to be studied to improve conservation of the species: 1) How many beetles are there per unit area? 2) Are the beetles also found in the denser vegetation away from the vernal pools?
ACTIVITY PATTERNS: 3) When do the beetles make their initial appearance, and when are they last seen each year? 4) Where do they spend the rest of the year? 5) When they are present, are they more active during certain periods? 6) At what time of year, and under what circumstances, do the beetles fly?
FEEDING BEHAVIOR AND PREDATORS: 7) What are the major food items for the adults and larvae throughout the year? 8) What are the major predators for the various life stages? 9) What other species compete for food or space?
REPRODUCTION AND LONGEVITY: 10) What is the reproductive season? 11) Where are the eggs laid and what is their incubation period? 12) How many eggs are laid per female and can she lay more than one clutch per season? 13) What are the morphological characteristics of the different life stages? 14) When and where do the larvae pupate? 15) What is the ratio of males and females in each color morph? 16) What is the life span?
Many of the above questions may be answered by Larry Serpa who conducts ongoing research. (See address in MONIT.REQS.) Dr. Richard Arnold (50 Cleveland Rd. #3, Pleasant Hill, CA 94523, (415) 823-3784) is also studying this species. Dr. David Kavanaugh of the California Academy of Sciences (Golden Gate Park, San Francisco, CA 94118, (415) 221-5100 ext. 228 or 229) is a very helpful specialist on carabid beetles.
Biological Research Needs: Systematic surveys, population monitoring, and demographic monitoring are needed. Analysis of habitat features associated with delta ground beetle observations and research on habitat management strategies in the Jepson Prairie Preserve are needed (USFWS, 2005).
Needs: Control invasive nonnative plants within the Jepson Prairie Preserve; perhaps improve habitat by fire; restoration initiatives (USFWS, 2005).
Relevance to Humans and Ecosystems
Stewardship Overview: Stewardship needs in order of priority are: 1) Protect adjacent lands inhabited by the beetle; 2) Reduce grazing pressure on the protected lands; 3) Elucidate as much as possible about the life history and ecology of the species; and 4) Monitor the beetle populations. This Recovery Plan uses an ecosystem-level approach because many of the listed species and species of concern co-occur in the same natural ecosystem and share the same threats. Management objectives of the recovery plan (USFWS, 2005) include: (1) Habitat Protection: accomplish habitat protection that promotes vernal pool ecosystem function sufficient to contribute to population viability of the covered species (suitable vernal pool habitat within each prioritized core area for the species is protected; species localities distributed across the species geographic range and genetic range are protected and protection of extreme edges of populations protects the genetic differences that occur there; reintroduction and introductions must be carried out and meet success criteria; additional localities are permanently protected, if determined essential to recovery goals; habitat protection results in protection of hydrology essential to vernal pool ecosystem function, and monitoring indicates that hydrology that contributes to population viability has been maintained through at least one multi-year period that includes above average, average, and below average local rainfall as defined above, a multi-year drought, and a minimum of 5 years of post-drought monitoring), (2) Adaptive Habitat Management and Monitoring (habitat management and monitoring plans that facilitate maintenance of vernal pool ecosystem function and population viability have been developed and implemented for all habitat protected; mechanisms are in place to provide for management in perpetuity and long-term monitoring; monitoring indicates that ecosystem function has been maintained in the areas protected for at least one multi-year period that includes above average, average, and below average local rainfall, a multi-year drought, and a minimum of 5 years of post-drought monitoring), (3) Status Surveys (status surveys, 5-year status reviews, and population monitoring show populations within each vernal pool region where the species occur are viable and have been maintained (stable or increasing) for at least one multi-year period that includes above average, average, and below average local rainfall, a multi-year drought, and a minimum of 5 years of post-drought monitoring; status surveys, status reviews, and habitat monitoring show that threats identified during and since the listing process have been ameliorated or eliminated and site-specific threats identified through standardized site assessments and habitat management planning also must be ameliorated or eliminated); (4) Research (research actions necessary for recovery and conservation of the covered species have been identified and research actions on species biology and ecology, habitat management and restoration, and methods to eliminate or ameliorate threats have been completed and incorporated into habitat; research on genetic structure has been completed and results incorporated into habitat protection plans to ensure that within and among population genetic variation is fully representative by populations protected; research necessary to determine appropriate parameters to measure population viability for each species have been completed); (5) Participation and outreach (Recovery Implementation Team is established and functioning to oversee rangewide recovery efforts; vernal pool regional working groups are established and functioning to oversee regional recovery efforts; participation plans for each vernal pool region have been completed and implemented; vernal pool region working groups have developed and implemented outreach and incentive programs that develop partnerships contributing to achieving recovery criteria). The majority of the known Conservancy fairy shrimp localities are not currently managed under management plans. None of the known localities have sufficient funding for systematic monitoring to determine habitat quality or species status trends. In most cases, threats to this species, such as those described above, will not be detected and managed for.
Delta green ground beetle
The Delta green ground beetle (Elaphrus viridis) is a species of ground beetle restricted to a small region within Solano County, California. Its color is a metallic-green, usually with bronze spots on its elytra, though some lack these spots. The lack or reduction of circular pits on the elytra helps distinguish it from other ground beetles. Typical adults are about a quarter-inch (0.6 cm) in length.
Range and distribution
The Delta green ground beetle is known to only occur in Solano County, though it may have historically occurred throughout the Central Valley. It is known to inhabit Jepson Prairie Preserve, south of Dixon, where it is protected; however, the beetle's other known ranges are located on public land.
The beetle occupies vernal pool habitats, around which its life cycle is based: it emerges in January following the filling of vernal pools from winter rains and lies dormant in May (around when the pools dry up) as a means of surviving the summer.
Specimens of the Delta green ground beetle have generally been collected in open habitats, namely the edges of vernal pools and nearby trails, roads and ditches. They may also be present in the surrounding grasslands, but the beetle's small size, camouflage against spring grass, and tendency to hide beneath low growth make it difficult to locate.
The Delta green ground beetle, in both its larval and adult stages, actively hunts soft-bodied arthropods. Based on the habits of other species of Elaphrus, it is likely that the beetle feeds primarily on springtails.
The Delta green ground beetle's current IUCN Red List status is Critically Endangered, owing to the species' extremely limited range and the endangerment of its vital vernal pool habitats. In addition, the species has been federally listed as threatened since 1980.
The destruction of vernal pool habitats in California is largely the result of agricultural development, though urbanization and grazing have played some role in their elimination. Another significant threat to the beetle is the introduced Garden lippia, which grows in dense mats in these habitats and impairs its ability to forage.
- "Delta Green Ground Beetle, Elaphrus viridis". Sacramento Fish & Wildlife Office. Retrieved on 14 August 2006.
- "California's Endangered Insects - Delta Green Ground Beetle". Essig Museum of Entomology - UC Berkeley. Retrieved on 14 August 2006.
- "Species Elaphrus viridis - Delta green ground beetle". BugGuide. Retrieved on 14 August 2006.
- World Conservation Monitoring Centre (1996). Elaphrus viridis. 2006. IUCN Red List of Threatened Species. IUCN 2006. www.iucnredlist.org. Retrieved on 14 August 2006. Database entry includes justification for why this species is listed as critically endangered.
Names and Taxonomy
Comments: See Goulet (1983) for a revision of the tribe Elaphrini.