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UPCOMING OPPORTUNITY:
Join us for another
Winter Hummingbird Expedition to Costa Rica
in November/December 2005 or February 2006

HUMMINGBIRD MORNINGS
Informative and entertaining hummingbird banding presentations are coming up in August 2005 in South Carolina, Virginia, Maryland & Kentucky/Tennessee.
(Click on the logo at left for details.)

SPINED OAK BORER:
A REAL LONGHORN

If you've ever been to the tropics, a favorite attraction at many lodges is a series of wires and walkways that meander through the tree canopy. For folks who aren't acrophobic, a canopy tour is thrilling for many reasons. It's a rush to be a hundred feet in the air, of course, but from a scientific standpoint it's a terrific way to see tree-top organisms we seldom encounter at ground level. We always thought it would be neat to have an observation deck high in our tallest oak trees at Hilton Pond Center, if only to see what kinds of birds and insects might be flitting about in top-most branches. We've never had opportunity to construct such an aerial platform, so we have to content ourselves with enticing canopy dwellers to come down to us. One way is to set up an ultraviolet "black light" against a white bedsheet near the base of a tree, in the hope some insects will be attracted to a "fake moon." Such was the case this week when an incredible beetle came down from its normal habitat and landed on the sheet long enough for us to scrape it gently into a jar--all the better to examine and photograph our newly found "long-horned" insect.

All text & photos © Hilton Pond Center

We knew at first glance our six-legged capture was indeed a member of the Long-horned Beetle Family (Cerambycidae), shown about four times life-size in the photo above. To be honest, calling this little insect's antennae "long" is an understatement; the beetle itself was only about three-quarters of an inch in length, but each extended, tapering antenna was twice as long as its body. Longhorn, indeed!

There are reportedly more species of beetles than any other insect order--some sources claim a quarter of all named animal species are in the Beetle Order (Coleoptera)--so it's not always easy to identify beetles in-hand. We were fortunate at least to be able to narrow our new beetle to the long-horn family level, but there are nearly 300 genera and 1,200 species of cerambycids--and that's just in North America. A variety of characters--especially a barrel-shaped pronotum (i.e., the exoskeleton over the thorax, or middle body section)--put our catch into the Cerambycinae, or Round-necked Long-horns. Members of this subfamily--of which there are about 450 North American species--are primarily tree-dwellers; they're also tree-EATERS, especially in the larval stage.

Not being coleopterists or having a good beetle key to follow, our attempt to identify the beetle to species followed a time-honored procedure of comparing it to photos in whatever insect field guides we had on-hand. Because we couldn't find an acceptable match, we posted an inquiry on an insect listserv and learned from beetle field guide author Dr. Doug Yanega of University of California-Riverside our beetle was a Spined Oak Borer, Elaphidion mucronatum--whose common name comes in part from the spiny projections on several antenna segments (above right) and its "knees" (femoral leg segments).

Spined Oak Borers occur from New York to Michigan and south to Florida. The adult has massive pinching mandibles (above) that apparently are used to work on dead branches of various hardwood trees, including towering oaks. We've been unable to learn whether the adult beetle actually eats the wood, or if this important decompositional work is performed only by its larvae--hence the name "Spined Oak BORER." This species lays its eggs under bark scales on dead tree limbs, after which the larvae spend their first year feeding just under the bark; during the second year, the larve migrate deeper into the dead wood, pupate, and eventually emerge as adults.

One thing we HAVE surmised is that the specimen pictured herein is likely a male, which we deduced by its extremely long antennae. Although such extended sensory structures might be a secondary sex characteristic that helps attract females, we suspect instead that longer antennae sense odor and help males do a better job of finding prospective mates when the females exude chemical pheromones.

As always, we welcome additional knowledge our readers may have about our weekly topic and will update this installment if any new tidbits about the Spined Oak Borer are forthcoming. In the meantime, instead of going into the treetops to meet more beetles where they live, we'll just continue nighttime operation of our ground-level ultraviolet light trap. This should entice additional insects down from the tall oaks at Hilton Pond Center, and we suspect we'll find even more species of long-horned beetles clinging to the bedsheet.

All text & photos © Hilton Pond Center