Datana

Adults distinguished from similar Notodontidae by wing pattern and genitalia; specific identification often requires dissection. Larvae recognizable by gregarious feeding habit, long soft body hairs, and characteristic damage pattern of skeletonizing leaves or consuming entire leaf blades. Distinguished from fall webworm (Hyphantria cunea) by absence of silken webbing; from walnut caterpillar (Datana integerrima specifically) by timing and host association. Species-level identification of larvae challenging without rearing to adult.

Deciduous hardwood forests, riparian woodlands, orchards, and urban landscapes with host trees present. Associated with oak, hickory, pecan, walnut, and other hardwood species. Adults often found near larval host plants; attracted to light.

North America, primarily United States and southern Canada. Species distributed across eastern, central, and southwestern regions. Records from Vermont westward across the continent, with concentration in eastern and central deciduous forest regions. One species (Datana chiriquensis) extends to Central America (Panama).

Adults active primarily in late spring through summer, with flight periods varying by species and latitude. Larvae present from mid-summer through early fall, with late-season defoliation characteristic. Single or multiple generations per year depending on species and climate; most appear to be univoltine or bivoltine.

Larvae feed on leaves of hardwood trees, particularly Fagaceae (oaks, Quercus spp.; beeches, Fagus spp.), Juglandaceae (walnuts, Juglans spp.; hickories, Carya spp.; pecans, Carya illinoinensis), and occasionally other woody plants. Specific host associations vary by species. Adults do not feed.

• Quercus - larval food plantoaks
• Carya - larval food planthickories and pecans
• Juglans - larval food plantwalnuts
• Fagus - larval food plantbeeches

Eggs laid in masses on undersides of leaves. Larvae hatch and feed gregariously, consuming leaf tissue. Full-grown larvae descend to ground and pupate in soil or leaf litter, often in silken cocoons incorporating debris. Adults emerge following pupal diapause. Overwintering stage typically pupa or egg, varying by species.

Larvae exhibit gregarious feeding behavior, often consuming leaves in groups and producing conspicuous frass accumulation. When disturbed, larvae may drop from foliage on silken threads. Late-instar larvae may disperse individually. Adults nocturnal, attracted to artificial light sources. Females release pheromones for mate location.

Primary consumer and defoliator in deciduous forest ecosystems. Population outbreaks can cause localized defoliation, though typically with minimal long-term tree health impact. Serve as prey for generalist predators and parasitoids including birds, predatory insects, and parasitic wasps. Documented as prey for thread-waisted wasps (Ammophila spp.). Contribute to nutrient cycling through frass deposition and leaf litter processing.

Several species are occasional pests of pecan orchards and ornamental hardwoods. Datana integerrima (walnut caterpillar) and D. ministra (yellow-necked caterpillar) are the most economically significant. Defoliation can reduce nut fill in pecans and aesthetic value in landscape trees. Management rarely required; mechanical removal or targeted insecticide application used when necessary. Larvae and frass may cause nuisance in residential areas during outbreaks.

• AnisotaBoth genera contain late-season defoliators with gregarious larvae; Anisota larvae have prominent thoracic horns and different color patterns (often orange stripes), and produce less conspicuous frass.
• LochmaeusSimilar late-season defoliator genus in Notodontidae; Lochmaeus larvae have different body shape and prominent humps, with more irregular feeding pattern.
• DryocampaAnother Notodontid defoliator; Dryocampa larvae are solitary or in small groups, with distinct coloration (often green with red horns), and feed earlier in season.
• Hyphantria cuneaFall webworm builds extensive silken webs enclosing foliage; Datana larvae do not construct webs, producing only silken escape threads when disturbed.
• MalacosomaTent caterpillars construct dense silken tents in branch crotches; Datana larvae lack this behavior and have different body hair characteristics.

• defoliator
• forest pest
• gregarious larvae
• Notodontidae
• hardwood feeder
• late-season

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Insects and mites that feed on leaves - AgriLife Extension Entomology
• Bug Eric: Wasp Wednesday: Ammophila procera
• Much Ado About Nothing? End-of-Summer Defoliation Heats Up
• Bug Eric: November 2010
• 2018 Arizona Insect Collecting Trip “iReport” | Beetles In The Bush