Sunday, October 17, 2010
Laurel Sphinx Moths are found throughout Eastern North America. This one was photographed in August at work. It had been attracted to the mercury vapor light pointed out our flag. The next morning it was hanging from the Russian Sage. These are a modestly beautiful moth, certainly not extravagant in their coloring, or in their size, yet pretty just the same. They are sometimes called the Fawn Sphinx, which I assume comes from their fawn-like coloring. They are yellowish-brown in color, with dark margins on their forewings. There is also a bold white line on their forewings, and the hindwings are tan with a dark border. Their wingspan is up to 4 1/16 inches.
They can be found in woodland, yards and nurseries. They are often found around ornamental lilacs, which explains why I found a caterpillar of one of these moths hanging on my lilac bush. This particular moth was being used as a host to the brachonid wasps. Sphinx moth caterpillars are often chosen by these wasps as a host. Brachonid wasps are parasitoids, the females will use their ovipositor to lay eggs under the skin of the caterpillar. The eggs hatch and feed on the caterpillar from the inside. Once the caterpillar has been almost entirely devoured from within these tiny larvae will bore through the skin of the caterpillar and form capsule-like cocoons on the outside of the caterpillar. These tiny white, oval-shaped cocoons will remain on the caterpillar throughout its final days...within a week the wasps will hatch and shortly thereafter the caterpillar will die. It seems a horrific way to die, but it is a normal process in the life of the wasp and a means of biological control of the sphinx moths.
The caterpillars of the laurel sphinx feed on lilac, privet, ash, fringe tree, and plants in the olive family. Adults will nectar at honeysuckle, and bouncing bet. They will be seen hovering over the blooms at dusk and late evening.
To say that these wasps are terrible is to say that the moths are good. In the case of these creatures neither is an apt description, they are merely doing what they do best, and that is survive by any means possible. In the case of the moth death is eminent, but the wasps will go on to carry out future generations. For me, as a naturalist and lover of all insects it was a rare and exciting glimpse into their lives.