A beetle found only in elderberry thickets in the Sacramento Valley will remain on the federal list of Threatened species, the U.S. Fish and Wildlife Service announced Wednesday. The valley elderberry longhorned beetle, Desmocerus californicus dimorphus, is in trouble due to conversion of its habitat to farms and cities.
USFWS had proposed in 2012 to take the beetle off the Threatened species list, citing an apparent increase in local populations of the subspecies. As we reported in May, conservation groups challenged that proposal, saying that USFWS was using bad science to determine where the beetle still lived.
In Wednesday's decision, USFWS essentially ceded that point to critics of the delisting, saying that the 2012 proposal to strip the beetle of Endangered Species Act protection "did not fully analyze the best available information."
"Threats to the species and its habitat have not been reduced such that removal of this species from the Federal List of Endangered and Threatened Wildlife is appropriate," said USFWS in Wednesday's decision. The 2012 proposal to delist the beetle came in response to a 2010 petition by the Pacific Legal Foundation, an opponent of endangered species protection.
The most damning scientific criticism of the proposed delisting centered on USFWS' willingness to accept beetle "exit holes" in elderberry stems as evidence of the beetles' presence in an area.
The beetles lay eggs on the stems of mature blue elderberry shrubs, and their larvae burrow through those stems, eating the elderberries' soft wood. When the larvae are ready to pupate they tunnel almost all the way out of the stem, creating an exit hole with just a thin layer of bark covering it. They then head back into the hole, plug it with woodshavings, and pupate inside the stem.
When the adult beetle emerges from the pupa it clears aside that debris and chews its way through the bark, creating the "exit holes" that USFWS had been taking as evidence that the beetles were there.
Of 36 local populations of the valley elderberry longhorn beetle USFWS cited in its 2012 proposal to delist the subspecies, 21 were declared existing populations based solely on the presence of exit holes, with no sightings of adult beetles. But as both conservation groups and USFWS' scientific peer reviewers pointed out, those exit holes are virtually indistinguishable from those made by the closely related California elderberry longhorn beetle, which is relatively common.
In addition, concedes USFWS in Wednesday's decision, some of the exit holes cited as evidence of extant valley elderberry longhorn beetle populations were in dead elderberry stems, while the beetle only uses live stems to rear its young.
"We're grateful to see the Fish and Wildlife Service following the science and making the right decision to continue protections for this clearly imperiled beetle and its vanishing habitat," said Jeff Miller of the Center for Biological Diversity, which had opposed the delisting. "This is exactly how the process of peer review is supposed to work."