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Moth of the Week
Fall Webworm
Hyphantria cunea
The fall webworm is in the family Erebidae. Described by Dru Dury in 1773, this moth is known for creating webbed nests as caterpillars and living in them until the pupa stage. They are considered pests in some areas due to their tendency to defoliate trees while feeding as larva and are known as an invasive species in East Asia.
Description Adult moths are mostly white in color with white legs that are black/brown and white in color. The top two legs are orange on the segment closest to the body. Under the eyes are patches of the same orange color and on occasion there are orange spots on the abdomen. In the north, the wings are completely white while in the south, the wings are speckled with brown or black spots.
Average wingspan: 38.5 mm (≈1.5 in)
Diet and Habitat The fall webworm feeds on just about any type of deciduous tree and can defoliate entire beaches or trees. In the eastern U.S., these moths prefer pecan trees, black walnut, American elm, hickory, fruit trees, persimmon, and sweetgum. In the west, alder, willow, cottonwood and fruit trees are commonly eaten. Adult moths do not feed.
This species is native to North America, ranging from Canada to Mexico, was introduced into other continents in the 1940s, and has since then spread. First recorded in 1949, this moth was introduced to the former nation of Yugoslavia and spread from France to the Caspian Sea and further into central Asia: Turkmenistan, Uzbekistan, Kyrgyzstan, and southeastern Kazakhstan. When introduced to Japan in 1945, it spread to generations per year since its arrival.[5] It spread into China, southern Mongolia, Korea and southern Primorsky Krai of Russia. Now it is considered holarctic, meaning found in almost all regions of the Northern Hemisphere.
Mating The mating season starts in late June and lasts until early July. In the northern part of North America, this species has one generation per year. The larvae hatch and live in late summer through early fall. In the south, which is cons to be under an approximate latitude of 40°N, there are two or more generations annually and nests appear progressively earlier the further south you go. Male fall webworms are typically only available for mating for about 30–60 minutes per day. This moth even shows a form of fall parental behavior. The female will try to protect the eggs after oviposition by covering her newly laid eggs with her abdomen hairs. Females lay the eggs on the underside of the host plants’ leaves in groups of about 100.
Predators The fall webworm has many predators such as Monomorium minimum, Vespula spp., Coleomegilla maculata, and Rogas hyphantriae.This species is parasitized by around 50 species, such as the flies Musca domestica and Muscina stabulans, and parasitic wasps such as Chouioia cunea and Therion morio. There are also several species of microsporida (unicellular spore parasites) such as Nosema necatrix Kramer, Weiser, and Nosema bombycis that are harmful. This species is also harmed by several viruses such as granulovirus and nucleopolyhedrosis virus. The caterpillars protect and defend themselves by shaking and jerking together, giving off a repellant scent, and irritants on their hairs or spines.
Fun Fact The fall webworm is a social insect as groups of caterpillars live in spun nests made from webs. These webs have many benefits like finding of mates, temperature regulation, increased growth rate, and protection from predators. However they also result in higher rates of infections and predation.
(Source: Wikipedia, USDA Forest Service, Missouri Department of Conservation)
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