Valley Elderberry Longhorn Beetle

The valley elderberry longhorn beetle (Desmocerus californicusdimorphus ) (fig. 2) is a rare longhorn beetle, known from only a few localities in the lower Sacramento and upper San Joaquin valleys in California. These beetles are restricted to riparian areas, where the larvae are obligate stem and root borers of elderberry (Sambucus sp.). The adults feed on the foliage of the same plant.

Figure 2.
The valley elderberry longhorn beetle ( Desmocerus
californicus  dimorphus ). (Photo by F.G. Andrews.)

The habitat of this longhorn beetle occurs in areas with relatively high human population density and intensive agriculture. Much of the Central Valley riparian vegetation, of which elderberry is a conspicuous component, has al-

ready been lost, primarily to urban and agricultural development. Extensive loss of essential habitat for this rare species during historical times and the continuing threats to its remaining habitat were major forces in the decision of the US Department of the Interior to list this species as Threatened in 1980. Loss of elderberry groves continues as agricultural and urban development expand. Construction of industrial parks, bicycle trails, and parking lots all take their toll on the beetle's shrinking habitat. Obviously, some critical density of elderberry plants is required for the maintenance of the beetle's populations; however, studies to determine that necessary density have yet to be undertaken.