Orgyia leucostigma

Orgyia leucostigma, the white-marked tussock moth, is a moth in the family Erebidae. The species was first described by James Edward Smith in 1797. The caterpillar is very common especially in late summer in eastern North America, extending as far west as Texas, California, and Alberta.[1]

White-marked tussock moth
Adult
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Lepidoptera
Superfamily: Noctuoidea
Family: Erebidae
Genus: Orgyia
Species:
O. leucostigma
Binomial name
Orgyia leucostigma
(J. E. Smith, 1797)
Synonyms
  • Phalaena leucostigma J. E. Smith, 1797
  • Hemerocampa leucostigma
  • Cladophora leucographa Geyer, 1832
  • Acyphas plagiata Walker, 1855
  • Orgyia wardi Riotte, 1971
  • Orgyia oslari Barnes, 1900
  • Orgyia libera Strecker, 1900


Etymology

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 forelegs like arms.

Life cycle

Two or more generations occur per year in eastern North America.[2] They overwinter in the egg stage.

Eggs

Eggs are laid in a single mass over the cocoon of the female, and covered in a froth.[2] Up to 300 eggs are laid at a time.

Larvae

The larvae are brightly colored, 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 gray-brown hair pencil is at the hind end. Touching the hairs sets off an allergic reaction in many humans.[2] Young larvae skeletonize the surface of the leaf, while older larvae eat everything except the larger veins.[3] They grow to about 35 mm long.

Pupae

The caterpillars spin a grayish cocoon in bark crevices and incorporate setae in it. The moths emerge after two weeks.

Orgyia leucostigma in larval stage
Orgyia leucostigma in larval stage
Orgyia leucostigma in larval stage
Orgyia leucostigma in larval stage
Orgyia leucostigma in larval stage
Caterpillar in Michigan (June)
Caterpillar in Texas (April)

Adults

The females have reduced wings and do not leave the vicinity of the cocoon. The males are gray with wavy black lines and a white spot on the forewings (the vapourer, Orgyia antiqua, is similar but is a rusty color.) The antennae are very feathery. Moths are found from June to October.

Host plants

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.[2] Defoliating outbreaks are occasionally reported especially on Manitoba maple and elm in urban areas.[3] Outbreaks are usually ended by viral disease.


White-marked tussock moth on a willow tree in Iowa

Ecology

The fungus Entomophaga maimaiga was introduced to North America to control the gypsy moth (Lymantria dispar). The fungus also infects O. leucostigma[4] 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.[5]

Subspecies
  • 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)
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gollark: That would be very worrying.
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gollark: Well, the UK is moving into the "ignore it and hope it goes away" phase shortly.

References
  1. "Orgyia leucostigma (white-marked tussock moth)". CABI Invasive Species Compendium. CABI. 2019. Retrieved 4 August 2019.
  2. Wagner, D. M. (2005). Caterpillars of Eastern North America. Princeton University Press.
  3. 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.
  4. Hajek, A. E.; Strazanac, J. S.; Wheeler, M. M.; Vermeylen, F. M.; & Butler, L. (2004). "Persistence of the fungal pathogen Entomophaga maimaiga and its impact on native Lymantriidae". Biological Control. 30 (2): 466–473.
  5. Medina, R. F. & 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.
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