Ash Meadows Naucorid

Ambrysus amargosus

Description

The Ash Meadows naucorid, Ambrysus amargosus, is a small, dark-colored aquatic insect of the family Naucoridae, order Hemiptera. It is 0.2 in (0.5 cm) in length and superficially resembles a common brown water bug with a flat back and oval carapace.

Behavior

This species lives its complete life cycle in an aquatic habitat. It feeds on plant matter. All life stages feed on small aquatic insect larvae and other benthic arthropods, including spiders, centipedes, and millipedes.

When submerged, it breathes from air stored under its wings.

Although little is known about its life history or habitat requirements, food for closely related naucorids includes aquatic insect larvae that are preyed upon while the bug swims over and through the substrate. Reproduction occurs during early spring and summer. Female naucorid bugs deposit demersal eggs that adhere to the substrate during incubation.

Habitat

The Ash Meadows naucorid has been found only in a single warm spring and associated outflow streams with rock and gravel substrates. This aquatic insect is known to occupy an extremely restricted habitat where flowing water passes over rock and pebble substrates at Point of Rocks Springs.

Distribution

There is no evidence that this species ever occurred in other springs or streams of the Ash Meadows region in Nevada. Most Ash Meadows springs are cold, while this species requires thermal waters. Channelization of spring flows for irrigation and other purposes has restricted the original habitat.

This naucorid is found only at Point of Rocks Springs and its outflow streams in east-central Ash Meadows. During the late 1970s a developer dammed the Point of Rocks Springs outflow to supply a planned residential and resort community of 55,000. Although this project was eventually abandoned, the natural streams inhabited by the naucorid were lost, and the species is now restricted to several narrow artificial channels less than 33 ft (10 m) long. Approximately 10 acres (4 hectares) at Point of Rocks Springs are designated critical habitat for the species. There is no current population estimate.

Threats

The small size and vulnerability of its habitats makes the naucorid highly susceptible to extirpation. One threat to the naucorid's survival is potential groundwater depletion, which would decrease spring flows. In 1982, it was found that users were certified to consume more water per year than the Ash Meadows aquifer actually discharged. If users drew the maximum amount of water allowed, the habitats supporting the Ash Meadows flora and fauna would be destroyed. Subsequently, the courts acted to limit the amount of groundwater that could be pumped from the aquifer.

Conservation and Recovery

The remaining habitat of the Ash Meadows naucorid falls within the Ash Meadows Wildlife Refuge. About 10 acres (4 hectares) has been designated as critical habitat for the species, including Point of Rocks Springs and its immediate outflows. The federally listed Ash Meadows Amargosa pup-fish (Cyprinodon nevadensis mionectes ) shares the same spring outflow area with the naucorid.

Contact

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

References

La Rivers, I. 1953. "New Gelastocorid and Naucorid Records and Miscellaneous Notes with a Description of the New Species, Ambrysus amargosus (Hemiptera: Naucoridae)." The Wasmann Journal of Biology 11: 83-96.

U. S. Fish and Wildlife Service. 1985. "Determination of Threatened Status with Critical Habitat for Six Plants and One Insect in Ash Meadows, Nevada and California; and Endangered Status with Critical Habitat for One Plant in Ash Meadows." Federal Register 50 (97): 20777-20794.