The Delhi Sands flower-loving fly (Rhaphiomidas terminatus abdominalis) is named for the very specific habitat it requires - Delhi series sands occurring only on the Delhi Sands formation in southwestern California, an area of ancient inland dunes. This sand type currently exists only in San Bernardino and Riverside counties in southern California.
At 2.5 cm long, the Delhi Sands flower-loving fly is one of the largest flies in the world. It is orange-brown and black with dark brown oval spots.
Currently 12 populations exist and this species is the only fly on the Endangered Species List. It was federally listed in 1993. Ninety-seven per cent of this species' habitat has been destroyed. Development, agricultural conversion, sand mining, invasion by exotic species, dumping of cow manure and trash, and off-road vehicles continue to threaten the species.
endemic to a single state or province
Regularity: Regularly occurring
Type of Residency: Year-round
Global Range: (<100-250 square km (less than about 40-100 square miles)) Currently occurs in southwestern San Bernardino and northwestern Riverside counties in California, an eight mile radius, but is presumed to have once occurred throughout the Colton Dunes, a 40 square mile area (USFWS, 1993).
Length: 2.5 cm
Comments: Found in "...fine, sandy soils, often with wholly or partly consolidated dunes". (USFWS, 1993). Restricted to a particular soil type classified as the 'Dehli' series.
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.
Number of Occurrences
Note: For many non-migratory species, occurrences are roughly equivalent to populations.
Estimated Number of Occurrences: 1 - 5
Comments: Five populations known to exist (USFWS, 1993).
Life History and Behavior
Very little is known about the biology of this fly. Adults are active for a few weeks during August and September. A female lays up to 40 eggs in the sand and larvae hatch 11 to 12 days later. The larvae develop entirely below ground - this stage is believed to last for two years before adults emerge.
National NatureServe Conservation Status
Rounded National Status Rank: N1 - Critically Imperiled
NatureServe Conservation Status
Rounded Global Status Rank: T1 - Critically Imperiled
Reasons: Range has been dramatically reduced to a handful of sites that continue to be threatened by local development.
Date Listed: 09/23/1993
Lead Region: California/Nevada Region (Region 8)
Where Listed: Entire
Population location: Entire
Listing status: E
For most current information and documents related to the conservation status and management of Rhaphiomidas terminatus abdominalis , see its USFWS Species Profile
Global Short Term Trend: Decline of 30 to >90%
Comments: Range has been reduced by over 97% (USFWS, 1993). Most of the former habitat was destroyed by conversion to agriculture in the area (USFWS, 1993).
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: Threatened by construction of new homes, businesses, and roads. Small population size also leaves this species susceptible to loss of genetic variability (USFWS, 1993).
Global Protection: None. No occurrences appropriately protected and managed
Comments: All occurrences are on privately owned land.
Relevance to Humans and Ecosystems
Although not much is known about its biology, the fly is a known nectar feeder that hovers like a hummingbird as it feeds and flies quickly between flowers. It uses its long proboscis (a hollow straw-like organ) to suck nectar from flowers, and has been seen hovering over many native wildflowers in its habitat. However, the only flower the fly has been documented to nectar from is common buckwheat (Ermogonum fasciculatum), although other plants like California croton (Croton californicus) and telegraphweed (Heterotheca grandiflora) are also flowering during adult flying times and are potential nectar sources for the fly. Placement of the Delhi Sands flower-loving fly on the Endangered Species List has helped stop development projects in the remaining Delhi Sands habitat, a unique ecosystem which is home to other species with limited distribution, including the legless lizard (Anniella pulchra), San Diego horned lizard (Phrynosoma coronatum blainvillii), Delhi Sands metalmark butterfly (Apodemia mormo new subspecies), Delhi Sands Jerusalem cricket (Stenopelmatus new species), convergent apiocerid fly (Apiocera convergens), and the Delhi Sands sandroach (Arenivaga new species).
Delhi Sands flower-loving fly
This subspecies is restricted to the Delhi Sands formation, an area of ancient inland dunes of which only a few hundred acres out of more than 40 square miles (100 km2) remain. The rest largely now form much or all of the foundation on which the towns of Colton, Fontana, Rancho Cucamonga, California and Ontario, California are built. The adults are only active for a few weeks each year, feeding on flowers, in August and September.
This fly was emergency-listed by the United States Fish and Wildlife Service on September 23, 1993, and it has been an extremely contentious listing ever since. Political officials and news services from the region have repeatedly decried this fly as a disease-carrying pest, despite documentation that it is not. There have been repeated attempts by local officials to have the species de-listed. For example, Congressman Joe Baca proposed removing the Delhi Sands flower-loving fly off the Endangered Species List to encourage development.
Residential and commercial development, agricultural conversion, sand mining, invasion by exotic species, dumping of cow manure and trash, and off-road vehicle use have resulted in significant loss and modification of the species' habitat. Estimates are that over 97% of the original habitat is already gone, and only a portion of what remains is suitable habitat for these flies.
There are an estimated 5–10 more species of insects endemic to the Delhi Sands formation, including newly discovered and still unnamed species of scarab beetle, sand roach, and Jerusalem cricket.
- Baca bill aims to swat bothersome fly. Pe.com (2011-03-21). Retrieved on 2011-07-10.
- Baca wants Delhi Sands Flower-loving flies off list. Sbsun.com. Retrieved on 2011-07-10.
- Baca wants Delhi Sands Flower-loving flies off list. DailyBulletin.com (2010-03-09). Retrieved on 2011-07-10.
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