Friday, October 16, 2009
Emesaya, Thread-legged Bug
At the Benfield Land, where I was harvesting Autumn Olive on Sunday, I couldn’t help but notice the activity of the fall insects. Dragonflies and grasshoppers were the most obvious but
there were many others, including some late season butterflies. I have the same insects in my garden, plus a lot of bumblebees and harvestmen (daddy longlegs), but the one I found to be most interesting is a Thread-legged Bug.
Name: There are over 60 species of insects in the group known as Thread-legged Bugs. The genus Emesaya, within that group, has five species in the U.S. It is in the family of Assassin bugs, most of which are appropriately named, but unlike its relatives, Emesaya has some other tactics. More on that later. This one is most likely to be Emesaya brevipennis from “brev” meaning short and “penna” meaning wing. It is the largest of the Emesaya species found in eastern North America and, as such, the easiest one to notice.
When and where found: I first found one of these critters in August last year on the house, beside my front door, in a spider web. It was clearly still alive and, despite my general policy of non-interference, I decided to set it free. The spider had plenty of food in its web. I learned later, after I had identified it. Again, this year I have one living around the front door. I call her Emma and check on her frequently. She has been there since September 4.
Distinguishing characteristics: Thread-legged bugs, true to their common name, have very long threadlike legs. In addition, they have long threadlike bodies. At first glance, they look like a small, delicate version of the walking stick insect. Those of you familiar with the walking stick would never describe it as hefty and yet, as nose-tackle is to running back, so walking stick is to Emesaya. The body of this one was well over an inch long and the first pair of legs extended in line with the body added another three-quarters of an inch. Those front legs are shorter than the others and are adapted for clutching prey and generally reserved for that activity. The insect walks on its other four legs. The antennae are long and thin and look like another pair of legs.
You may also get a clue to the identity of Emesaya by its location in barns, cellars, or old buildings where there are spider webs and by its very slow gait. The tortoise and the slug would have to be handicapped to make a fair race with Emesaya.
Swimming with the sharks: Most insects would avoid spiders if they could. Not so the Emesaya. It is a kleptoparasite – it raids spider webs and steals food the spider has already caught. I assume its touch is so light on the web that it doesn’t get stuck and the spider doesn’t sense its presence.
Sources: My favorite insect guide book, the Kaufman Field Guide to Insects of North America by Eric R. Eaton and Kenn Kaufman; Insects, Their Natural History and Diversity, Stephen A. Marshall; and my favorite insect website www.bugguide.net (search for Emesaya). ∆
© 2009 The Carlisle Mosquito