Valley Elderberry Longhorn Beetle

Status

Valley elderberry longhorn beetle (Desmocerus californicus dimorphus) is Federally-listed as Threatened under the Federal Endangered Species Act (August 8, 1980). At the time of listing the beetle was known from less than ten locations along the American River, Putah Creek, and the Merced River. After further study, it has been found to range from southern Shasta County southward to Fresno County. Adult beetles have been found up to 2,200 feet in elevation along the eastern portion of their range, in the Sierra Nevada foothills, and up to 500 feet in elevation along the eastern slope of the Coast Range.

Description

Valley elderberry longhorn beetle is a somewhat elongate insect with a cylindrical-shaped body and very long antennae. Males range in length (measured from front of head to end of abdomen) between 0.5 and 1 inch and have antennae that are about equal to the length of their body. Females are slightly larger in size than males but have somewhat shorter antennae. Adult males have red-orange wing covers with four elongate spots, while females have dark-colored wing covers.

Habitat Requirements

Valley elderberry longhorn beetle is usually found on or close to live elderberry shrubs (Sambucus spp.), which its host plant. Blue elderberry generally occurs as part of riparian habitats throughout the Central Valley and Sierra Nevada foothills regions, but is also found in some upland areas. Although this species is wide-ranging within California, the valley elderberry longhorn beetle is thought to be in long-term decline due to widespread disturbance and fragmentation of riparian habitats, and some upland habitats, which support the species.

Adult female valley elderberry longhorn beetles lay their eggs in crevices on the bark before dying a short time later. Upon hatching, the larvae tunnel into the shrub where they eat the interior wood. The larval stage may last up to two years, after which the larvae enter the pupal state and transform into adults. Adult beetles emerge from inside the wood of elderberry shrubs in the spring as their flowers begin to open. Adults are most active from March through June when they feed on elderberry foliage and mate.

In order for elderberry shrubs to be considered suitable habitat for the species, the shrubs generally must have stems that are 1.0 inch or greater in diameter at ground level. Use of the shrub by this species is rarely apparent and often the only exterior evidence of use by the beetle is an exit hole created by the larva just before the pupal stage. Exit holes made by the emerging adults are distinctive small oval openings that are approximately ¼-inch wide.

Local Occurrence

The valley elderberry longhorn beetle occur at the River Ranch and Lincoln Hills WHF preserves.