Anisota

Hübner, 1820

Oakworm Moths, Oakworms

Species Guides

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Anisota is a of giant silk moths in the Saturniidae, first described by Jacob Hübner in 1820. Their caterpillars are commonly known as due to their specialized feeding on oak foliage. The genus contains approximately 13 distributed across North America, including well-known species such as the orangestriped oakworm (A. senatoria), pink-striped oakworm moth (A. virginiensis), and spiny oakworm (A. stigma). Larvae are gregarious feeders and can cause noticeable defoliation of oak trees, particularly in late summer.

Anisota stigma by (c) John P Friel, some rights reserved (CC BY), uploaded by John P Friel. Used under a CC-BY license.Anisota by (c) Christine Young, some rights reserved (CC BY), uploaded by Christine Young. Used under a CC-BY license.Anisota by (c) 116916927065934112165, some rights reserved (CC BY), uploaded by 116916927065934112165. Used under a CC-BY license.

Pronunciation

How to pronounce Anisota: //æˈnɪsətə//

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Identification

Anisota are medium to large-sized Saturniids with furry bodies and relatively subdued coloration compared to other silk moths. Males have broadly feathery ; females have less-feathery, more thread-like antennae. Caterpillars are distinctive: most have prominent longitudinal stripes (orange, pink, or yellow depending on species) and paired fleshy horn-like behind the . The orangestriped (A. senatoria) has black and orange banding; the pink-striped oakworm (A. virginiensis) has pink lateral stripes; the spiny oakworm (A. stigma) has prominent branched spines.

Images

Habitat

Oak-dominated forests and woodlands, including urban and suburban landscapes where oak trees are present. Larvae are found on foliage of oaks; are often attracted to lights. Some occupy specialized —A. finlaysoni is restricted to alvar habitats (limestone plains) of the Great Lakes region.

Distribution

North America, with ranging from southern Canada through the eastern and central United States. A. senatoria occurs throughout eastern North America; A. virginiensis ranges from the Great Lakes region to Florida and Texas; A. stigma occurs in the eastern and central United States; A. finlaysoni has a restricted range in eastern Ontario; A. oslari occurs in the southwestern United States including Trans-Pecos, Texas.

Seasonality

emerge in spring and summer, with timing varying by and latitude. In Maryland, A. senatoria adults first appear in May from pupae, with a second producing adults later in summer. Late-season defoliation by caterpillars is most conspicuous from July through September.

Diet

Larvae feed exclusively on oak foliage (Quercus spp.), with some also recorded on hickory (Carya) and birch (Betula). Specific associations include: A. oslari on sandpaper oak (Quercus pungens var. vaseyana); A. senatoria on various oak species including pin oak (Q. palustris). do not feed.

Life Cycle

Complete with one to two per year depending on and location. Females lay on undersides of leaves. Larvae feed gregariously, initially skeletonizing leaves, later consuming entire leaves except major . Mature larvae drop to the ground, burrow into soil to pupate, and overwinter as pupae. emerge the following spring to mate and oviposit.

Behavior

Larvae are gregarious, feeding in clusters that can cause localized heavy defoliation. When disturbed, caterpillars may regurgitate or thrash. Mature larvae exhibit mass exodus , dropping from trees and crawling across ground surfaces to find sites—this makes them vulnerable to mortality on paved trails and roads. are and attracted to light.

Ecological Role

Larvae function as primary consumers of oak foliage, transferring energy from trees to higher . They serve as prey for numerous (ichneumon wasps, braconid wasps, tachinid flies) and (birds, spiders, predatory beetles). Natural enemies typically regulate , causing collapses. production contributes to nutrient cycling in forest .

Human Relevance

are occasionally significant defoliators of landscape and street trees, causing aesthetic damage and concern. have prompted programs in such as Norfolk, Virginia and Montgomery Village, Maryland. Mechanical removal of larval clusters or targeted applications (Bacillus thuringiensis, insecticides) are used when management is warranted. Late-season defoliation rarely causes lasting tree damage.

Similar Taxa

  • Dryocampa rubicunda (greenstriped mapleworm)Also a Saturniid with similar and late-season defoliation , but feeds on maple (Acer) rather than oak; larvae have green and white stripes rather than orange or pink
  • Lochmaeus spp. (tussock moths)Late-season oak defoliators with gregarious larvae, but have distinctive tussock hairs and different
  • Datana spp. (handmaid moths)Gregarious larvae that feed on oaks and other woody plants, but have smooth bodies with longitudinal stripes and different resting posture (rear end raised)

Sources and further reading