Delhi Sands Flower-loving Fly

Rhaphiomidas terminatus abdominalis

Description

The Rhaphiomidas terminatus abdominalis (Delhi Sands flower-loving fly) has an elongated body with a long tubular proboscis, which is used to extract nectar from flowers. This fly is about 1 in (2.5 cm) long, orange-brown in color, and has dark brown oval spots on the upper surface of the abdomen.

Behavior

The life history of this fly is not well known, but is probably similar to that of other members of this genus. These flies inhabit arid or semi-arid regions, and may occur in sparsely vegetated sand dune habitats. Adults take nectar from flowers by means of an elongate proboscis. The preference of the species for sparsely vegetated areas may be related to the insect's behavior of flying low, usually less than 3 ft (1 m) above the ground. The vegetation may aid in the selection of egg-laying sites.

Mating behavior has not been observed in the wild, although it is known that eggs are deposited in sand. In captivity a female produced over 50 eggs within a 10 day period. Larval development takes place in the sand and metamorphosis probably takes a full year.

This species is a strong flier and, like a hummingbird, is capable of stationary, hovering flight. The Delhi Sands flower-loving fly probably makes a single annual flight period during August and September. A skewed ratio of males to females (about 2:1) suggests that, as with many other insects, males are more active, spending much of their time flying and investigating vegetation or the sand surface for resting females. The single annual flight suggests that development to metamorphosis takes a full year. Pupas work their way to the surface prior to emergence as adults.

Habitat

The habitat of this fly is sandy, fine soils within or adjacent to consolidated dunes. These soil types are generally called "Delhi" fine sand. Delhi soils cover about 40 sq mi (103 sq km) in several irregular patches, extending from the cities of Colton to Ontario and Chino in northwestern Riverside and southwestern San Bernardino Counties. Much of the area of Delhi soils has been used for agriculture, chiefly grapes and citrus, since the 1800s. More recently, this area has been used for dairies, housing tracts, and industrial sites. Dominant vegetation includes wild buckwheat, croton, and telegraph weed.

Distribution

Based on this species' present distribution, it is thought that it once occurred throughout much of the entire area (40 sq mi [103 sq km]) of the Delhi fine sand soil.

This fly occurs in San Bernardino and Riverside Counties, California. Documented distribution of this insect extends from the eastern margin of the Delhi fine sand formation in Colton to near its western limit in Mira Loma.

The Delhi Sands flower-loving fly currently occurs at five locations in southern California: four in southwestern San Bernardino County, and one in Riverside County, just south of the San Bernardino County line. All known colonies occur on privately owned land within an 8 mi (13 km) radius circle.

Threats

The major threats to the Delhi Sands flower-loving fly are habitat loss and degradation. Historic and recent agricultural, residential, and commercial development have significantly reduced suitable habitat. Most of the former habitat was destroyed by agricultural development in the 1800s, and the remaining suitable habitat continues to be destroyed by the construction of homes and businesses, and their associated roads and infrastructure. Soil disturbances are being caused by grading, plowing, discing to remove vegetation for fire control, and off-road vehicle use. The use of off-road vehicles may also contribute to the loss of native vegetation and subsequent invasion of weedy, non-native species. Illegal dumping of abandoned automobiles and other trash has also contributed to habitat degradation.

The Delhi Sands flower-loving fly will not return to previously farmed areas. Agricultural fields may return or be restored to suitable habitat over time; however, the potential of this species to re-colonize degraded sites is unknown, although this behavior may be pivotal to its recovery.

The use of pesticides in agricultural areas and their persistence in the soil may have harmful effects on this species. Furthermore, the level of disturbance at a given site may favor exotic over native vegetation, which may preclude use by the fly.

Although flies in general are not especially popular with collectors, the Delhi Sands flower-loving fly is prized because of its unusual size, coloration, and rarity. A dedicated collector could readily eliminate this species, given its small isolated populations. Even scientific collecting, or repeated handling and marking, particularly of the females, could eliminate populations through loss of genetic variability. Collection of females dispersing from a colony could also reduce the probability that new colonies will be established.

Conservation and Recovery

The Fish and Wildlife Service published a Recovery Plan for the Delhi Sands flower-loving fly in 1997. Eight populations of this endangered insect are located in protected areas. However, most critical habitats are on private land and are at risk from development and other threatening activities, including the habitat of the largest known population. Conservation of the Delhi Sands flower-loving fly requires that these critical habitats be protected. This can be accomplished by acquiring the land and designating ecological reserves, or by negotiating conservation easements with the owners. The populations of the Delhi Sands flower-loving fly should be monitored, and research undertaken into its biology, habitat needs, and beneficial management practices. The Fish and Wildlife Service intends to implement a program of habitat improvement and captive-breeding and release, which will enhance the recovery of the rare insect.

Contact

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Building
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
Telephone: (503) 231-6121
http://pacific.fws.gov/

References

U.S. Fish and Wildlife Service. 23 September 1993. "Endangered and Threatened Wildlife and Plants; Determination of Endangered Status for the Delhi Sands Flower-loving Fly." Federal Register 58(183): 49881-49887.

U.S. Fish and Wildlife Service. 1997. "Delhi Sands flower-loving fly (Rhaphiomidas terminatus abdominalis ) Recovery Plan." U.S. Fish and Wildlife Service, Portland, OR.