Anisota senatoria

Smith, J.E., 1797

orangestriped oakworm, orange-tipped oakworm

Anisota senatoria is a Nearctic in the , commonly known as the orangestriped . It is one of the more common Saturniids in eastern North America, occasionally reaching pest status in the northern parts of its range. The is notable for being a late-season feeder on oak foliage, which limits its long-term impact on tree health. are sexually : females are larger, -orange with silver- spots and faint black across the , while males are smaller and reddish-. The species is very similar to A. finlaysoni in southern Ontario and A. peigleri in the southern United States.

Anisota senatoria by Greg Dwyer. Used under a CC BY-SA 2.5 license.

Adult-anisota-senatoria-moth by Tom Nicholaides. Used under a CC BY-SA 1.0 license.

Monograph of the bombycine moths of North America, including their transformations and origin of the larval markings and armature (1914) (14775875094) by Packard, A. S. (Alpheus Spring), 1839-1905;

Cockerell, Theodore D. A. (Theodore Dru Alison), 1866-1948. Used under a No restrictions license.

Pronunciation

How to pronounce Anisota senatoria: /ænɪˈsoʊtə sɛnəˈtɔriə/

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

distinguished from similar Anisota by pattern and geographic location. A. finlaysoni occurs in eastern Lake Ontario region and has distinct adult ; A. peigleri occurs in the southern US. identified by black ground color with -orange stripes, prominent thoracic horns, and gregarious feeding on oaks in late summer. Distinguished from greenstriped mapleworm (Dryocampa rubicunda) by and stripe color (orange vs. green).

Images

Habitat

Deciduous forests and urban landscapes dominated by oak trees. Found in both natural forest settings and highly visible urban areas such as parks, yards, and street tree plantings where oaks are present. require access to soil for , making paved surfaces a significant barrier to successful completion.

Distribution

Eastern North America, from the edge of the Great Plains to the Atlantic coast, and from southern Ontario south to central Georgia, Alabama, and eastern Texas. More common in northern portions of its range; present but less abundant in northern Florida.

Seasonality

emerge once annually from mid-June to mid-July. feed in August and September. One per year throughout most of range.

Diet

feed primarily on oaks (Quercus spp.), especially red oaks. Also reported from chestnut, birch, hazel, hickory, and maple. do not feed.

Host Associations

Quercus - primary larval especially red oaks
Castanea - larval chestnut
Betula - larval birch
Corylus - larval hazel
Carya - larval hickory
Acer - larval maple

Life Cycle

One per year. emerge mid-June to mid-July, mate during midday, and females lay on undersides of leaves in late afternoon. Eggs hatch in 1–2 weeks. feed gregariously in early , often remaining clustered in late instars. Fifth instar larvae descend from trees, burrow underground to pupate, and overwinter as . Nutritional studies indicate late-season feeding strategy favors over rapid growth rate, with consumption rate increasing in response to decreased nitrogen levels in mature foliage.

Behavior

exhibit gregarious feeding, particularly in early . When tree is complete, larvae wander to locate new host trees, often descending to ground and climbing adjacent trees. Mass larval exodus from trees creates significant mortality risk from ground-dwelling and human-created obstacles such as paved trails. accumulation beneath infested trees can be substantial, producing audible sounds like raindrops in forest settings.

Ecological Role

Late-season defoliator of oaks. As late-season feeders, they do little lasting damage to because most energy has been stored by trees already. Serves as host for (particularly ) that help regulate . Contributes to through deposition. Provides food source for various including birds, , and predatory .

Human Relevance

Occasionally reaches pest status in urban landscapes, particularly in northern range. can be unsightly and accumulation on sidewalks, patios, and driveways creates nuisance. programs have been developed in such as Norfolk, VA and Montgomery Village, MD. (hand-picking or pruning infested branches) often sufficient; rarely needed. Paved trails and roads create artificial mortality sources for wandering larvae, though public awareness can mitigate impacts.

Similar Taxa

Anisota finlaysoniVery similar in appearance; occurs in southern Ontario. Distinguished by and restricted range in eastern Lake Ontario region, separated by ~200 km gap from A. senatoria .
Anisota peigleriVery similar; occurs in southern United States. Geographic separation and subtle morphological differences distinguish the .
Dryocampa rubicundaGreenstriped mapleworm has similar and habit of gregarious late-season feeding, but distinguished by green stripes (vs. orange), different plants (maples vs. oaks), and appearance.

More Details

Taxonomic Complexity

boundaries within the Anisota senatoria species-group have been historically problematic. Recent research indicates A. finlaysoni has a much smaller range than previously believed, with Lake Erie re-assigned to A. senatoria. barcodes do not reliably discriminate species in the senatoria-group.

Nutritional Ecology

Compared to spring-feeding oak defoliators like Alsophila pometaria, A. senatoria exhibits a feeding strategy favoring over rapid growth rate. Unlike A. pometaria, whose growth rate is directly related to leaf nitrogen content, A. senatoria growth rate is independent of leaf nitrogen, with consumption rate increasing to compensate for lower nitrogen in mature foliage.