Ailanthus Webworm Moth

Atteva aurea – Ailanthus Webworm Moth – Hodges#2401

Ailanthus webworm mothAilanthus webworm moth is the lone representative of this genus in North America. This very common moth ranges from Ontario and New York south to Florida, west to Nebraska and Texas, and south into Mexico. Gregarious larvae are found in communal webs on their host plant, Ailanthus, aka tree of heaven, stinking sumac, or varnish tree.Ailanthus webworm moth on sedumAilanthus, often planted as a fast-growing ornamental, this Asian native has become invasive in North America. This hardy native moth has quickly adapted and expanded its range and numbers along with the inexorable march of the tree. I don’t often see them here in Northern Illinois, but when I do, they are always taking nectar at flowers. Shown here on sedum and field goldenrod.
Ailanthus webworm moth
I like to get up close to my bugs, using a hand held flash. The blue iridescence you see in the scales bordering the white spots are barely visible in daylight, but the flash reveals hidden details at higher magnification. Always use the smallest “sweet spot” aperture you can, and shoot at the slowest shutter speed possible without getting motion blur. (It’s easy to mistake blur for out-of-focus.) The sweet spot aperture on my Canon 100mm macro lens is f16, so I shoot at 1/60 if possible to avoid the pitch black background. That’s where the flash really helps “freeze” the scene. Of course, if it’s windy or the bug is moving rapidly, you’ll have to increase your shutter speed accordingly.

Ailanthus webworm is a member of the Family Yponomeutidae (Ermine Moths).  Wingspan= 19mmAilanthus webworm mothThe striking orange markings are thought to be aposematic, that is, warning colors advertising toxicity or weaponry. Predators know to avoid certain prey who exhibit these colors, e.g., the viceroy & monarch butterflies share orange aposematic coloring with a wide variety of insects that obtain their chemical defenses from feeding on milkweed; yellowjacket wasps and the flies that mimic them the all share bold yellow and black aposematic paint jobs.

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