Friday, June 25, 2010
Old Home Day festivities start tomorrow and the theme is “Treasures of Carlisle.” Of the hundreds of species reported so far in the Biodiversity Corner, most of them should be considered treasures of Carlisle. I recently saw a coleopteran treasure that definitely qualifies for the grand parade. On June 18 Leslie Thomas captured it in her garden on Prospect Street and saved it for me. I later released it in my yard on School Street (so it won’t have far to travel to join the parade).
Name: The beetle was an Eyed Elater, a member of the Elateridae family informally known as Elaters or Click Beetles, Skipjacks and Jack-knife beetles (more on that later). Beetles are a hugely successful group of animals. There are around 24,000 species in North America. Within this family alone, there are 965 documented species and another hundred waiting for formal recognition. Of the known species, there are at least five Eyed Elaters, so named because they have a pair of large eye-spots on the thorax. This one is the largest and most striking. It is Alaus oculatus.
Identifying characteristics: This is one of the easiest beetles to identify. It is large – almost an inch and a half long not counting antennae. The large black eye spots on the thorax are made even more conspicuous by their white eye-liner and are designed to give pause to potential predators. The rest of the beetle is shiny black with white specks. The legs and saw-edged antennae are also black. The sides of the abdomen are more or less parallel. Once you have seen one, even in a picture, you will know it the next time you see one.
Life cycle: Adult Eyed Elaters are harmless beetles. They survive on nectar and plant juices. They lay their eggs in soil and the larvae find their way to decaying wood presumably not far from where they hatched. The larvae look like wireworms. They are predators and eat the larvae of other beetles, like wood borers. Other species of Elaters have the kind of wireworm larvae that can be a nuisance in the garden because they eat roots and seeds.
Twist and shout: The reason Elaters are also known as Click Beetles (or Skipjacks or Jack-knifes) is because they have a flexible thorax and a long spring-loaded peg attached to the underside of the thorax and held by a “latch” between the middle legs. When necessary, either to right itself when turned over or to escape a predator, the beetle bends itself backwards into an arch until there is enough pressure on the peg to suddenly break it free from the latch. This results in a loud click and sends the whole beetle hurtling end-over-end into the air. Even when you are expecting it, it can be a bit startling.
Other species of Elaters (or Click Beetles) are much more common than this one. If you find a dull brown beetle that is more long and narrow than it is short and stout, you can give it the click test. I have found two in my garden in the last few days and they both passed the test. All you do is touch the beetle and watch to see if it pulls its legs under its body and drops to the ground. If it lands on its back watch carefully and listen to see if it clicks, jumps and rights itself. This is often easier to see if you pick the beetle up and place it carefully on a flat surface like the palm of your hand. It may click and jump as you are trying to pick it up. If it flies away when you touch it, it is probably some other kind of beetle. If it just lies there, the test is inconclusive.
This particular Alaus oculatus didn’t pass the test. It had been in a jar for half a day and probably had no energy left. It did recover well though, and seemed content to crawl on my hand or just sit on my arm. I was able to take it on a mini-tour of School Street and show it to my neighbors. Before nightfall I set it free in the flower garden. “See ya later, Eyed Elater.”
Sources: Kaufman Field Guide to Insects of North America, Eric R. Eaton, Ken Kaufman; Insects: Their Natural History and Diversity, Stephen A. Marshall; BugGuide.net (an excellent website for insects and ID assistance).
Submissions: Please feel free to claim this space and write the Biodiversity Corner on any species that occurs in the wild and you have found in Carlisle. ∆
© 2010 The Carlisle Mosquito