|White-marked tussock moth|
(JE Smith, 1797)
Orgyia leucostigma (white-marked tussock moth) is a moth in the family Erebidae. The caterpillar is very common especially in late summer in eastern North America, extending as far west as Texas, California, and Alberta.
The genus name Orgyia is from the Ancient Greek word ὄργυια, órgyia - 'outstretched arms'. So named because, when at rest, the moth stretches forward its fore legs like arms.
Two or more generations occur per year in eastern North America. They overwinter in the egg stage.
The larvae are brightly coloured, with tufts of hair-like setae. The head is bright red and the body has yellow or white stripes, with a black stripe along the middle of the back. Bright red defensive glands are seen on the hind end of the back. Four white toothbrush-like tufts stand out from the back, and a grey-brown hair pencil is at the hind end. Touching the hairs sets off an allergic reaction in many humans. Young larvae skeletonize the surface of the leaf, while older larvae eat everything except the larger veins. They grow to about 35 mm long.
The caterpillars spin a grayish cocoon in bark crevices and incorporate setae in it. The moths emerge after 2 weeks.
The females have reduced wings and do not leave the vicinity of the cocoon. The males are grey with wavy black lines and a white spot on the forewings (the vapourer, Orgyia antiqua, is similar but is a rusty colour.) The antennae are very feathery. Moths are found from June to October.
The caterpillars may be found feeding on an extremely wide variety of trees, both deciduous and coniferous, including apple, birch, black locust, cherry, elm, fir, hackberry, hemlock, hickory, larch, oak, rose, spruce, chestnut, and willow. Defoliating outbreaks are occasionally reported especially on Manitoba maple and elm in urban areas. Outbreaks are usually ended by viral disease.
The fungus Entomophaga maimaiga was introduced to North America to control the gypsy moth Lymantria dispar. The fungus also infects O. leucostigma and could possibly have an impact in years when E. maimaiga is abundant. Large larvae are mostly attacked by birds, and small larvae mostly disappear during dispersal.
- O. l. leucostigma (South Carolina, from Georgia and Florida to Texas)
- O. l. intermedia Fitch, 1856 (from Maine and Ontario to Virginia, Alberta and Kansas)
- O. l. plagiata (Walker, 1855) (Nova Scotia, New Brunswick, Quebec)
- O. l. oslari Barnes, 1900 (New Mexico, Colorado)
- O. l. sablensis Niel, 1979 (Sable Island, Canada)
- "Orgyia leucostigma (white-marked tussock moth)". CABI Invasive Species Compendium. CABI. 2019. Retrieved 4 August 2019.
- Wagner, DM. (2005). Caterpillars of eastern North America. Princeton University Press.
- Rose, AH and OH Lindquist. (1982). Insects of eastern hardwood trees. Canadian Forestry Service, Forestry Tech Rep 29. Government of Canada, Ottawa. ISBN 0-660-11205-1.
- Hajek AE, Strazanac JS, Wheeler MM, Vermeylen FM, Butler L. (2004). Persistence of the fungal pathogen Entomophaga maimaiga and its impact on native Lymantriidae. Biological Control 30(2):466–473.
- Medina RF, Barbosa P. (2002). Predation of small and large Orgyia leucostigma (J.E. Smith) (Lepidoptera : Lymantriidae) larvae by vertebrate and invertebrate predators. Environmental Entomology 31: 1097–1102.
-  Images of adults and larvae