Datana integerrima

Grote & Robinson, 1866

Walnut Caterpillar Moth

Datana integerrima, commonly known as the walnut , is a North in the . The moths have a wingspan of 35–50 mm and are active from May to August. The are notable defoliators of walnut, hickory, and other hardwood trees, feeding gregariously in large groups. While capable of causing significant , single-season rarely cause lasting damage to healthy trees.

Datana integerrima by (c) Christopher Zacharias, some rights reserved (CC BY), uploaded by Christopher Zacharias. Used under a CC-BY license.

- 7907 – Datana integerrima – Walnut Caterpillar Moth (16225575455) by Andy Reago & Chrissy McClarren. Used under a CC BY 2.0 license.

Datana integerrima by Jacy Lucier. Used under a CC BY-SA 4.0 license.

Pronunciation

How to pronounce Datana integerrima: //dæˈtænə ɪnˌtɛɡəˈraɪmə//

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Identification

are distinguished from other Datana by examination; external features are subtle. can be identified by their distinctive color progression (reddish- young to black adults with gray hairs), lack of web-building, and gregarious feeding . The combination of (walnut, hickory, oak) and the characteristic massing behavior on trunks and branches to helps separate them from similar defoliators like fall (Hyphantria cunea), which builds conspicuous silken webs.

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Habitat

Deciduous forests and woodlands, particularly those containing walnut (Juglans), hickory (Carya), and oak (Quercus) . Also found in urban and suburban settings where trees are planted, including parks and residential areas. require access to host foliage and will move to lower trunk and scaffold branches to congregate and .

Distribution

Eastern North America, ranging from Ontario south through most of the eastern United States, west to Minnesota, and south to northern Mexico.

Seasonality

are on from May to August. are present during summer months, with timing varying by latitude. In southern portions of the range, multiple may occur; northern typically have one generation annually.

Diet

feed on leaves of Carya (hickory), Juglans (walnut), Quercus (oak), Salix (willow), and Gleditsia triacanthos ( ), as well as some shrubs. do not feed.

Host Associations

Carya - larval Hickory
Juglans - larval Walnut ; primary reference
Quercus - larval Oak
Salix - larval Willow
Gleditsia triacanthos - larval

Life Cycle

Females masses of 500 or more eggs on undersides of leaves. Eggs hatch in approximately 10 days. feed for about 25 days, progressing through five . Young larvae feed gregariously on foliage. Full-grown larvae crawl to the soil to pupate, where they overwinter. emerge the following spring.

Behavior

exhibit strong , feeding in groups and congregating in large masses on tree trunks and scaffold branches to shed their skins () synchronously. This congregation is highly visible and often the first sign of noticed by observers. Final larvae consume the majority of foliage and can defoliate branches rapidly. Larvae do not construct protective webs or tents.

Ecological Role

As a defoliator, D. integerrima contributes to in deciduous forests. Severe can temporarily reduce photosynthetic capacity of trees, but healthy trees typically recover without long-term consequences. The serves as for various including , birds, and other . in soil may be consumed by ground-foraging .

Human Relevance

Considered a minor pest of walnut and pecan orchards, where larval feeding can reduce nut fill and the following year's production if is severe. In residential settings, the conspicuous larval masses and associated accumulation create aesthetic concerns. Control is rarely necessary in natural forests; in managed settings, or mechanical removal may be employed when threaten . The has been documented as for the thread-waisted Ammophila procera, which provisions nests with paralyzed .

Similar Taxa

Fall webworm (Hyphantria cunea)Both are late-season defoliators with hairy , but fall constructs conspicuous silken webs enclosing foliage, while D. integerrima larvae do not build webs and instead congregate on trunks to .
Other Datana speciesSeveral Datana overlap in range and use; accurate identification of to species often requires rearing to or examination of subtle morphological characters.
Anisota senatoria (orangestriped oakworm)Another gregarious late-season defoliator, but Anisota have prominent orange stripes and horns, differing from the black-and-gray coloration of mature D. integerrima.

Misconceptions

Despite the and reputation as a pest, single-season by walnut rarely causes lasting harm to healthy trees. The conspicuous larval masses often trigger unnecessary . Additionally, the is sometimes confused with fall due to similar plants and timing, but the absence of web-building in D. integerrima is a distinguishing feature.

More Details

Pest management considerations

In pecan and walnut orchards, for masses with flashlight of leaf undersides at night can facilitate early . Control is most effective when targeted at young ; larger larvae are more difficult to kill with and have already completed most of their feeding damage.