Thursday, November 11, 2010

Coneheads

In the summer and fall, one can encounter coneheads in and around fields here in Indianapolis. Or they might even visit your porch in the evening, if you have a light on.

No, not that kind of conehead! No need to fear an alien invasion of any sorts.

This is the kind of conehead I am talking about, a type of katydid. They are related to grasshopers and crickets. They are insects, not aliens, but they do have some bizarre alien-like body parts. I encountered this particular conehead on a hike a few weeks ago.

First of all, the forehead of a conehead is pretty distinct. It is, well for lack of a better description, ummm, cone-shaped. Compared to another katydid below, an Angle-wing Katydid , one can easily see the difference. They have a "conical fastigium" if you want to get technical or impress your friends. Or, you can just say they have a "pointy head".

Angle-wing Katydid, photo by John Howard

Coneheads have super long antennae that are chock-full of special sensors. There are chemoreceptors that detect pheromones and other scents and tactile receptors or "feelers"to interpret the physical environment. There is also the Johnston's organ located on the base of the antennae that is important in flight for sensing gravity, air speed and even the specific wing beats of a potential mate.

The female above, a Round-tipped Conehead, Neoconocephalus retusus, sports a long sword-like appendage called an ovipositor. Conehead females use the ovipositor to deposit eggs into the crowns of grass clumps. These eggs will overwinter and hatch out the following spring.

One of the weirdest cosmic adaptations of katydids (and crickets) are their "ears". They are not located on their head like ours, but on their front legs. They are called tympana. If you look on my photo above, the tympanum is the pale yellow patch located right below the leg joint or what would be our elbow.

You can see it a bit better in Wil Hershberger's beautiful photo of a Robust Conehead, above. The tympana are used to hear potential mates and other neighboring conehead's calls. The tympana can also detect vibrations in the vegetation, letting the conehead know there may be a predator nearby. The tympana can pick up ultrasonic vibrations like those produced by a hungry bat. In response to ultrasonic vibrations, coneheads will immediately stop singing. If they are in flight, they will quickly tuck in their wings and dive to the ground.
Coneheads produce sounds by a process called stridulation. On the bottom of one wing is a toothed structure called a file and on the top of the opposite wing is a raised structure called a scraper. When the conehead rubs its wings together, the file is drawn across the scraper causing the wings to vibrate producing sound. Each species of conehead produce a distinct song. To see a great photo of the file and scraper of a katydid, check out the photo here at Wil's site. It is halfway down the page. To hear a Round-tipped Conehead's call go HERE. To hear the call of the Robust Conehead, Neoconocephalus robustus, go HERE.

Coneheads are such fascinating creatures with interesting body parts. Hopefully, you will be fortunate enough to encounter one.
Thanks to Wil Hershberger for the use of his photo of the Robust Conehead and John Howard for the use of his angle-wing photo. Thanks a bunch, Wil and John!
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3 comments:

Bug Eric said...

Great post, Janet! These are among my favorite insects, too :-)

Wil said...

Terrific post. The coneheads are amazing insects. If only we knew why they had such elaborate head structures.
Wil

Janet Creamer said...

Thanks, Eric and Wil. I really appreciate your comments. It sounds like a good graduate project for a college student, Wil!