Whoever said little moths were all brown and ugly clearly has never seen this lovely critter. This bright, boldly patterned creature looks more like a roll of batik fabric than a fragile little moth in my opinion. And it’s a moth that actually comes out during the day!

This beautiful little moth that only reaches about half an inch long, is the Ailanthus Webworm Moth, Atteva aurea. While the word “aurea” in the species name translates to “golden”, the moth certainly looks very brightly orange to me. Maybe it refers to the “golden” white pattern on the wings? I’m sure it’s not because I found it on goldenrod flowers lol. The bright colors on the moth’s wings, both the orange and the white/yellow/”golden” do serve a purpose though. The bold “warning colors” (=aposematic coloration) are the moth’s way of telling predators back off – I taste bad!, which is pretty useful when you’re an otherwise defenseless plant-eater, and pollinator.

The moth tastes bad because its caterpillars (aka baby moths) mostly eat the chemical filled trees in genus Simarouba, also known as Bitterwood trees and Paradise Trees. I’m not particularly familiar with this group of trees, but that may be because they are mostly tropical trees. This makes sense since the family the Ailanthus Webworm Moth is in is called the Tropical Ermine Moths (family = Attevidae), which are also primarily found in more tropical areas. So wait - why am I then finding a tropical colored, tropical plant-eating moth, from a tropical family, on a super chilly (~45°F) fall day in Michigan??

The answer is tied to the reason the Ailanthus Webworm Moth is usually considered a beneficial insect – and it’s not because it’s pollinating my remaining goldenrod flowers (although I do love pollinators!). In addition to Paradise Trees, Ailanthus Webworm Moth caterpillars also feed on a notoriously invasive, introduced tree species. The Tree of Heaven tree, Ailanthus altissima. Ahh. Now that’s a tree I’m familiar with. I didn’t realize the invasive tree had made it to Michigan, but apparently it has according to this map from EDDMaps (and the moth in my yard lol):

While the Ailanthus Webworm Moth is native to North and Central America, it used to be restricted to southern Florida through Costa Rica. Now, thanks to the spread of the not so heavenly Tree of Heaven, which it likes to eat, the brilliantly colored Ailanthus Webworm Moth can now be found throughout most of the US, and even into Canada! So, even though it’s unfortunate the invasive tree has made it this far north, I am glad to get to see this pretty little native moth following its path and trying to help us humans combat an invasive tree that threatens to push out many of our native plant species.

To read more about the Ailanthus Webworm Moth, check out:

• BugGuide
• Missouri Department of Conservation

To read more about the invasive Tree of Heaven, check out:

• USDA Invasive Species Information Center
• The Nature Conservancy

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