Valley Elderberry Longhorn Beetle

Desmocerus californicus dimorphus Fisher, 1921
Date of listing: 1980
Federal Status: Threatened
State Status: None

The Valley Elderberry Longhorn Beetle (Coleoptera: Cerambycidae) is a medium-sized (about 2 cm long) beetle. The ‘dimorphus’ in its name refers to differences in appearance between the males and females. The forewings of the male are primarily red with dark green spots, whereas those of the female are dark metallic green with red margins.

This beetle is associated with elderberry trees (Sambucus spp.) in California’s Central Valley during its entire life cycle. The adults emerge in the spring from pupation inside the wood of these trees as they begin to bloom. The exit holes made by the emerging adults are distinctive, small oval openings. Often these holes are the only clue that the beetles occur in an area. The adults eat the elderberry foliage until about June when they mate. The females lay their eggs in crevices in the bark. Upon hatching, the larvae then begin to tunnel into the tree where they will spend 1-2 years eating the interior wood, their sole source of food.

In the Central Valley, the elderberry tree is associated with riparian forests which occur along rivers and streams. Historically the beetle ranged throughout the Valley, but recent surveys have revealed the beetle to persist only in scattered localities along the Sacramento, American, San Joaquin, Kings, Kaweah, and Tule rivers and their tributaries. Over 90% of our riparian forests have been cleared in the past century for agricultural, urban, and suburban development. The wood from these forests has also been used extensively as fuel and building materials. Additionally, extensive use of pesticides, grazing and other mismanagement have severely degraded otherwise undisturbed patches of riparian habitat.

Current efforts to save the Valley Elderberry Longhorn Beetle have focused on revegetating riparian habitats. The California Department of Water Resources has assisted the U.S. Fish and Wildlife Service in replanting elderberry along parts of the American River. Efforts are currently underway to reintroduce the beetle itself into areas which it formerly inhabited. Some success has been achieved by transplanting inhabited trees to a site near Sacramento.

For further reading:
Barr, C. B., 1991. The distribution, habitat, and status of the Valley Elderberry Longhorn Beetle Desmocerus californicus dimorphus Fisher (Coleoptera: Cerambycidae). U.S. Fish and Wildlife Service. Sacramento, CA.

Eng, L. L., 1984. Rare, threatened and endangered invertebrates in California riparian systems. In: California riparian systems Ecology, conservation, and productive management, ed. R. E. Warner and K. M. Hendrix. Berkeley: University of California Press.


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