ailanthus webworm moth

not listed

NNR - Unranked

SNR - Unranked

not listed

Ailanthus webworm moth is a small, native, ermine moth with a colorful appearance and an unusual history. It was formerly native to the tropical Americas, including southern Florida, Central America, and the Caribbean, where its larval hosts were paradise tree (Simarouba glauca) and Simarouba amara. In 1784, the Chinese tree of heaven (Ailanthus altissima) was introduced into Philadelphia. The tree was fast growing and spread quickly. When it reached Florida in the 1850s, ailanthus webworm moth found it to be an acceptable host. The moths then began moving north to wherever their new host was found.

Ailanthus webworm now occurs throughout the United States east of the Great Plains, and in southern Quebec and Ontario Canada. It is common in the eastern United States, uncommon but increasing in Minnesota. Tree of heaven, which is often planted as an ornamental in urban areas, remains the primary larval host, but larvae have also been found on avocado, Emory’s crucifixion-thorn, and sumac. Adults are found visiting flowers from May to October in Minnesota. They can’t survive northern winters, but they recolonize the northern range of tree of heaven every year. Although its range has recently expanded greatly, ailanthus webworm moth is not considered invasive by any state or province.

Adults are 7⁄16″ to ⅝″ (11 to 15 mm) in length and have a 11⁄16″ to 13⁄16″ (18 to 30 mm) wingspan.

The forewings are reddish-orange with four broad black bands filled with white or pale yellow spots of varying size. The bright pattern is thought to be a warning to predators of their unpalatability. The black areas have bluish-purple reflections. The hindwings are mostly translucent with black on the margins and black veins.

Total length: 7⁄16″ to ⅝″ (11 to 15 mm)

Wingspan: 11⁄16″ to 13⁄16″ (18 to 30 mm)

Ornate moth (Utetheisa ornatrix) is superficially similar but larger. The forewings are crossed with rows of black spots bordered with white.

Several generations per year: May to October in Minnesota

The larvae create a shelter of a bundle of leaves secured with silk and feed communally inside the shelter.

Adults are active during the day.

Development from the egg to an egg-laying adult is just four weeks. Larvae pupate within their feeding shelter. Female adults deposit eggs one at a time on the same or on another shelter. One shelter may contain larvae of multiple generations.

Tree of heaven, avocado, Emory’s crucifixion-thorn, and sumac

Flower nectar

Sources

4, 21, 27, 29, 30, 75, 82, 83.

Although its range has recently expanded greatly, ailanthus webworm moth is not considered invasive by any state or province.

Common in the eastern United States, uncommon but increasing in Minnesota.

Atteva aurea was formerly recognized as two different species, Atteva ergatica in Costa Rica and Atteva punctella in North America. A recent DNA analysis (Wilson, 2010) determined that the DNA barcodes of the two species were identical, as were their morphology and their food plants. They also found that they formed a complex of overlapping species than could be separated where they co-occurred in Costa Rica. However, both species names were invalid, so the new name Atteva aurea was assigned to the species ranging from Quebec to Costa Rica, and the name Atteva pustulella was assigned to the species in Central America.

Atteva aurea ailanthus webworm moth

Atteva aurea, ailanthus webworm moth, on goldenrod flowers, Barnes Prairie, Racine Co., WI. Photos taken on October 13, 2020.

Location: Barnes Prairie, Racine Co., WI

Atteva aurea, ailanthus webworm moth, on goldenrod flowers, Barnes Prairie, Racine Co., WI. Photos taken on October 13, 2020.