Xavier Magazine

Beetle Mania: The Hunt for a Different Kind of Longhorn

Like a lot of entomologists, assistant biology professor Ann Ray has been bugged by a dearth of information about the valley elderberry longhorn beetle. So she joined a group of other bug-crazy biologists to find a better way to locate them than just looking in the weeds.

The valley elderberry longhorn beetle, whose Latin name is Desmocerus californicus dimorphus, is a threatened species, just a step below endangered. But there’s a catch—no one really knows how many there are.

“Since (the beetle was added to the threatened species list in 1980), it has been the subject of a lot of controversy because the larvae bore into elderberry trees,” Ray says. “Elderberry is a weed. It just grows up in all sorts of place. Since the beetle’s elderberry habitat is protected, you can’t cut down elderberry trees. But you also can’t develop.”

Property owners don’t like elderberry, but they can’t cut down the pesky weed because it’s the habitat of the longhorn. And yet determining exactly how threatened the longhorn is has been nearly impossible. Until now.

Who would have thought that the sex pheromone desmolactone could be the answer?

Entomologists use pheromones like desmolactone in special traps, where the pheromone is hung in a cross-section of cardboard. The beetles are attracted to the pheromone and hit the cardboard as they fly, falling into the trap. Only the male beetles are attracted to the traps. It’s a far more effective way to find specimens than hunting through elderberry trees.

Ray and her colleagues published an article on their discovery in the online journal PLOS One in December last year and hope it’s the answer to finding—and studying—the valley elderberry longhorn beetle. And maybe freeing up the elderberry for a much-needed trim. Read the journal article at PLOS One.


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