Cupedids: Triassic relics in our backyards

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Cupedid Tenomerga cinerea from Ithaca, NY.

Some exciting nature discoveries come with equally thrilling stories of pursuit through field and forest. Others involve no adventuring at all, no action-packed hunt or anything. Such has been the case with my encounters with the odd beetle family Cupedidae. These insects’ strange biology and evolutionary history, however, more than make up for any excitement lost in capture, for cupedids are one of the oldest relic beetle families in the world. Their fossils date back to the Triassic Period 199 million years ago, and their basic structure hasn’t changed a whole lot since then. At first glance they resemble squared-off longhorn beetles (Cerambycidae), but the “reticulated” pattern of their elytra (hardenedforewings) and the little protuberances on their heads mark them as something very different. Cupedids tend to have long antennae and a parallel-sided body, and are covered in scaly setae. There are only 33 living species worldwide, 4 of which occur in the U.S. Two of those species, Priacma serrata and Prolixocupes lobiceps, live in the western U.S, while the other two, Tenomerga cinerea and Cupes capitatus, make their homes in deciduous woodlands of the east. Very little is known about how any cupedids make their living, but the few that have been studied feed on fungus-infested wood as larvae. Oddly, Priacma is supposedly attracted to household bleach, suggesting that some chemical component of bleach mimics one of the beetle’s pheromones. Undoubtedly there is much to be learned about these mysterious animals.

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Cupes capitatus (Kennebunk, ME)

I have been fortunate enough to see both eastern U.S. species of Cupedidae, but unfortunately there is not much to say about my finding of either. My first and only Cupes capitatus was found sitting on the wall of my old middle school in southern Maine back in July 2013. It lived for several weeks in captivity, but rarely did anything other than stand around on the piece of wood in its container. When I handled the beetle, it retracted its legs and played dead, often not moving again for hours. I found it a rather cute little animal, with its big eyes and knobby head. Cupes is actually the rarer of the two eastern cupedids (nothing is known about its larvae or food source!), so I half expected to find Tenomerga that year too. Instead, fast forward to July 2017, where I was walking behind a building on the Cornell University campus checking the lights for insects. Many spiders like to build their webs here to take advantage of the bounty, and I make it a point to see what they have caught, but I was shocked to spot a Tenomerga cinerea hanging from a strand! The spider was nowhere in sight, and the beetle was still alive as I carefully plucked it from the web. This cupedid acted much the same as the Cupes, just standing around and playing dead whenever handled. Unfortunately it only lived for about a week indoors. For those of you who might want to see these interesting beetles for yourselves, I have no special advice other than to spend a lot of time outdoors. It’s really just a matter of being in the right place at the right time.

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Tenomerga cinerea on its back, showing how neatly packaged the beetle appears when playing dead.

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