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Ambrysus amargosus , Ash Meadows Naucorid

Ambrysus amargosus: (6.0 – 6.5 mm), is also known as Ash Meadow Naucorid or the Ash Meadow creeping water bug is in the order Hemiptera, family Naucoridae. This bug is colored a dull brown with scattered dark yellowish markings on the head, thorax and legs. The forelegs are raptorial and are used mainly for prey capture while the mid and hind legs are modified for swimming in the water. A. amargosus is a flightless insect and has reduced hind wings and spends its complete life cycle in the water; it is a hemimetabolous insect. The insect breaths underwater by using a plastron, which has hydrophobic hairs that form a film of air around the abdomen which allows the insect to respire underwater. The film layer allows for the diffusion of carbon dioxide out of the air and oxygen into the air while underwater.

A. amargosus was first described by Ira La Rivers in 1953 from specimens taken at Point of Rock Springs, Nevada. The species is endemic to the area and is found nowhere else in the world. It is the only aquatic and hemipteran insect to be federally protected under the U.S. Endangered Species Act of 1973. It is classified as a threatened species and was placed on the list on May 20th, 1985.

The species was found throughout the thermal outflows in Ash Meadows. The Ash Meadows Wildlife Refuge is a combination of desert and a wetlands ecosystem. The wetlands in the middle of the desert are due to a huge underground aquifer. The aquifer discharges in refuge because a geologic fault creates an “underground dam” that blocks water and causes it to surface and create outflows. This creates a variety of habitats in the preserve. The original habitat range of A. amargosus consisted of scattered spring outflows which exited from a hillside and collected in small ponds. This habitat however was almost completely destroyed due the land being intensively farmed. The aquifer was channeled and used for crop irrigation drying out many of the ponds and outflows of water in the area. The wetland area of the refuge was also drained and mined for its vast amounts of peat. The refuge itself today is home to 24 different plants and animals species found nowhere else in the world.

There are many things that are still unknown about the behavior, food habits and reproductive biology which may be helpful in helping to conserve the species. There are many actions being taken by the wildlife refuge to help conserve A. amargosus. One of the major goals of the refuge is to restore the area to its natural historic condition. They have implemented a generalized plan for the recovery of endangered and threatened species of the refuge. The plan includes restoring and eventually delisting of endangered plant and animals populations on the refuge, restoring the wetland and desert upland habitats to what was found on the refuge 100 years ago, to provide a habitat for other migrating and resident wildlife and to remove exotic species from the area.


Written by: Carlos Domiguez, Spring 2006

Image credit: NA