A naturalist reveals some of the wonders of the natural world found right around the Washington, DC Metropolitan area using his own photography and his life-long experiences. I invite you to also check out my Facebook Group "Capital Naturalist" or YouTube Channel (https://www.youtube.com/channel/UCv8LHf1hHCEU3UHdpb-8Mng) or follow me on Twitter: @CapNaturalist.
Saturday, September 20, 2014
Ailanthus Webworm Moths
Ailanthus Webworm Moth on Goldenrod
While most moths fly at night and are drab, a few don't follow that trend. One of these is a colorful daytime flying moth called the Ailanthus Webworm Moth (Atteva aurea). These are very common and very visible from now through the Fall, especially favoring goldenrod to nectar at. They are one of the few native insects that has benefited from the introduction of an invasive alien exotics plant, the Ailanthus, or Tree-of-Heaven.
Formerly, Ailanthus Webworm Moths were limited to areas where their original caterpillar food host plant, the Paradise Tree (Simarouba glauca and Simarouba amara), grew in the tropics to Southern Florida. When the Ailanthus Tree (Ailanthus altissima) was introduced from China, it was similar enough that the caterpillars were able to feed on it. In fact, now the caterpillars are so associated with the widely spreading invasive plant that even their common name reflects this. The caterpillar and moth are now found well outside their original range and are as common as their exotic pest host plants.
The moth is quite colorful, likely as a warning that it is distasteful due to the chemicals it ingests from its food plants. People often confuse it for a butterfly because of its diurnal nature and colors. It loves to nectar at such plants as goldenrods, asters, ironweeds, and other blooms, performing some minor pollination services.
Ailanthus Webworm feeding inside its web on Ailanthus (Tree-of-Heaven)
The caterpillars fold together several leaves and wrap them in webs, feeding inside this protective shelter. Although this is the only plant they eat in our region, they rarely do much real damage to the tree itself and are not really a natural control for this invasive pest plant.
I enjoy seeing these colorful moths now in our region and take some pleasure that their caterpillars feed on the invasive tree. Rare is the case where invasive species provide much benefit to native creatures, in fact the contrary is almost always the case. Helping this moth expand well outside its native range does not make up for the damages the invasive plants cause. Regardless, it is good to know that at least one creature has had this luck and adds its colors to those in our meadows, fields, and roadsides.