I had an interesting find a couple of weeks ago when I noticed a tiny, colorful moth visiting a salvia flower in my yard. I started looking around and discovered several more of the moths on chrysanthemums. It was the Ailanthus webworm moth, Atteva aurea, a member of the Family Yponomeutidae, the ermine moths. I am going to call it AWM simply because it is easier than writing out its name.
These moths are not very common unless there are Ailanthus trees nearby. The AWM is a day-flying moth and pollinates many flowers as it visits them to drink nectar. I have only spotted them a few times on isolated instances, and this was just a matter of being in the right place at the right time.
Here is one thing to keep in mind when you find an unusual adult insect. The adult stage is for reproduction, so insects have to find each other for mating. For that reason, they need to be in the same place at the same time. Adulthood for most insects is usually a very short period, sometimes only lasting days or even hours. So, if you see one type of insect, you can usually find more like it if you take the time to look around carefully.
Ailanthus Webworm moths are not very common unless there are Ailanthus trees nearby. The AWM is a day-flying moth and pollinates many flowers as it visits them to drink nectar.
Journal photo by Claire Stuart
The ermine moths got their name because most of them are white with tiny black spots, resembling the ermine fur that royalty used to trim their robes. However, the AWM is very different. Once you have seen this lovely little creature, you will never forget it, because its patterns are so striking. It is bright orange, trimmed with what look just like little white flowers outlined in black. Its wings are extremely long and narrow. When it is not flying, it holds its wings rolled down over the sides of its body, making it rather resemble a narrow beetle.
AWM is native to southern Florida and Central and South America where its larvae feed on Paradise Trees (Simarouba glauca and Simarouba amara). Tree-of-Heaven (Ailanthus altissma), a native of China, is closely related to those trees. It was introduced to the U.S. in the late 1700s and was widely used as an ornamental and street tree. Unfortunately, Tree-of-Heaven soon turned into a pest plant. It grows extremely rapidly, reproduces quickly and spreads to push out other vegetation. Not only that, but it stinks!
Probably the only good thing to be said for Tree-of-Heaven is that it is drought and pollution-tolerant and it will grow just about anywhere, including sites with acid mine drainage, cement dust, mercury, high ozone, automotive fumes and other things that kill most trees. It is the tree in the title of the classic novel "A Tree Grows in Brooklyn" by Betty Smith that was made into a well-known movie in 1945.
As Tree-of-Heaven pushed its way over the US, the AWM moved north from its native trees to take advantage of this abundant food source. Since Tree-of-Heaven is considered an invasive pest plant, the AWM should be considered beneficial for eating it.
The AWM larvae are small, striped caterpillars that build communal nests by pulling leaves together with webbing. They eat leaves, flowers and seeds. They spin their cocoons within the shelter of their webs.
The AWM has more than one generation per year, but it is not known to spend winter in the northern states. Apparently it migrates south for the winter and a new generation follows warm weather all the way up into Canada the following spring.
Of course, it is too late in the year to see any more of these beautiful little moths, but you might keep them in mind and watch for them on flowers next year.
- Send your insect questions to Claire Stuart by email at email@example.com or write her (with self-addressed stamped envelope) in care of Living Section, The Journal, 207 W. King St., Martinsburg, WV 25401