Orgyia leucostigma
(Smith, 1797)
White-marked Tussock Moth
A to North America, distinguished by sexually : females are flightless with reduced , while males are winged and active. The is conspicuously colored with defensive hair tufts and can cause allergic reactions in humans. Multiple occur annually in eastern North America, with occasionally reported on urban trees.
Pronunciation
How to pronounce Orgyia leucostigma: /ɔrˈɡɪ.iə luːkoʊˈstɪɡmə/
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Identification
males distinguished from the similar Vapourer (Orgyia antiqua) by gray coloration rather than rusty ; both share the spot and feathery . identified by the combination of red , four white tufts, and red glands; no other eastern North larva matches this pattern. Females are flightless with reduced , unlike most moth species.
Images
Habitat
Found in diverse wooded including deciduous and coniferous forests, urban parks, and suburban areas. occur on trees across a range of forest and developed landscapes.
Distribution
Eastern North America from the Atlantic coast west to Texas, Colorado, and Alberta. Also reported from Europe and Taiwan. Multiple recognized across the range: O. l. leucostigma (southeastern), O. l. intermedia (northeastern and central), O. l. plagiata (Maritime Canada), O. l. oslari (southwestern), O. l. sablensis (Sable Island).
Seasonality
active from June to October. Two or more per year in eastern North America. most conspicuous in late summer. Overwinters as .
Diet
feed on an exceptionally broad range of including apple, birch, black , cherry, elm, fir, hackberry, hemlock, hickory, larch, oak, rose, spruce, chestnut, and willow. Young larvae leaf surfaces; older larvae consume all leaf tissue except major .
Host Associations
- Malus - larval foodplantapple
- Betula - larval foodplantbirch
- Robinia pseudoacacia - larval foodplantblack
- Prunus - larval foodplantcherry
- Ulmus - larval foodplantelm; defoliating reported on Manitoba maple and urban elm
- Abies - larval foodplantfir
- Celtis - larval foodplanthackberry
- Tsuga - larval foodplanthemlock
- Carya - larval foodplanthickory
- Larix - larval foodplantlarch
- Quercus - larval foodplantoak
- Rosa - larval foodplantrose
- Picea - larval foodplantspruce
- Castanea - larval foodplantchestnut
- Salix - larval foodplantwillow
Life Cycle
are laid in a single mass of up to 300 over the female's , covered with froth. Eggs overwinter. feed and develop through multiple . occurs in a cocoon spun in bark crevices; emerge after approximately two weeks. Females remain at the cocoon and emit to attract males; after mating and egg-laying, females die without dispersing.
Behavior
Females are flightless and exhibit extreme , remaining at their to mate and oviposit. Larval occurs by ballooning on threads. possess urticating that trigger allergic reactions upon contact with human skin.
Ecological Role
Defoliator of and coniferous trees; occasional can cause significant tree damage in urban areas. Outbreaks are typically terminated by viral . The four tufts of have been hypothesized to mimic the of parasitic , potentially serving as a visual defense against . Large larvae are preyed upon by birds; small larvae experience high mortality during . The Entomophaga maimaiga, originally released for spongy control, also infects this .
Human Relevance
Larval cause allergic dermatitis in sensitive individuals upon contact. Occasional defoliating on urban trees (particularly Manitoba maple and elm) generate management concern. The is not a major economic pest but can be a nuisance in residential areas.
Similar Taxa
- Orgyia antiquaSimilar gray male with spot and feathery , but O. antiqua has rusty coloration rather than gray; females similarly flightless.
- Orgyia pseudotsugataRelated with similar ; distinguished by distribution (western North America) and association primarily with Douglas-fir.
- Orgyia vetustaWestern with overlapping range in western North America; similar larval appearance but different geographic distribution.
More Details
Etymology
The name Orgyia derives from Greek ὄργυια (órgyia), meaning 'outstretched arms', referring to the posture of resting with forelegs extended forward.
Sexual dimorphism
Among the most extreme in : females are completely flightless with , while males are fully winged and active fliers. This has led to females being historically overlooked or described separately in early literature.