Lymantria monacha (Nun moth) - Factsheet
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Adult: Nun moths are moderately sized, hairy and often stout-bodied with a wingspan of 45 to 55 mm (female) or 35 to 45 mm (male).Footnote 1 Footnote 2 Moths have white forewings with numerous dark, transverse, wavy lines (arches) and patches. The hind wings are gray-white or gray-brown, with minute dark patches along the outer edge.Footnote 1 Footnote 2 Female antennae are short and saw-like, whereas male antennae are feathery.Footnote 1 Footnote 2 Females have a reddish-brown abdomen with black spots, males have a gray-black abdomen.Footnote 1 Footnote 2 Melanic gray-brown and black forms are also known to occur.
Larva: Mature larvae are light to dark brown and have an orange to pale-brown head with dense black markings. Larvae are 30 to 35 mm long. Numerous short black and white hairs are present; hairs on the prothoracic and anal segments are longer. The 1st four abdominal segments have a dorsal pair of small, bluish glandular protrusions; the 6th and 7th segments have prominent mid-dorsal, orange glandular warts.Footnote 1 Footnote 2 A dark dorsal band runs from the 2nd to the 11th segment.Footnote 1 Footnote 2
Prefers Picea, Larix, Abies, Pinus and Pseudotsuga.Footnote 2 Footnote 4 Will also feed on Acer, Betula, Carpinus, Fagus, Fraxinus, Malus, Prunus, Quercus, Ulmus and other fruit trees.Footnote 2 Footnote 4
Location of Infestation Within the Tree
Healthy trees.Footnote 2
China, Japan, North Korea, South Korea, Russia, Turkey and Europe.Footnote 2
Signs and Symptoms
Naked clusters of eggs may be found in bark crevices or under bark scales of trees and logs, wood packaging, forest products, sea containers and ships.Footnote 7 Egg clusters are not covered with the abdominal hair of females.Footnote 2 On coniferous trees, female nun moths preferentially oviposit on the lower bole, but during outbreaks oviposition will occur on the upper bole and in the crown.Footnote 5
First instar larvae will only feed on the foliage of newly expanded shoots and are unable to consume older needles.Footnote 2 Second and third instar larvae are able to feed on older foliage but prefer to feed on new needles.Footnote 2 Footnote 5 Larvae can be wasteful feeders and may only consume the base of a needle, resulting in partially uneaten needles falling to the ground.Footnote 4 The crowns of defoliated trees appear thinned and have a reddish-brown colour. During outbreaks, over 50% of the foliage can be defoliated. Severe defoliation over a few years can cause tree mortality.Footnote 5
A - Adult L. monacha. Note white forewings and numerous dark, transverse, wavy lines and patches.
B - Thin crowns caused by L. defoliation.
C - Mature dark brown L. monacha larva (30-35 mm long). Note mid-dorsal orange warts on the 6th and 7th segments.
D - Bark scale removed to reveal naked L. monacha egg mass.
E - L. monacha defoliation on understory host tree.
F - Extensive stand defoliation caused by L. monacha. Note thinning reddish-brown crowns.
G - Defoliation by late instar L. monacha. Note partially eaten needles.
- A Paul Schaefer, Beneficial Insects Introduction Research Unit, USDA Agricultural Research Service
- B Landesforstpräsidium Sachsen Archives, Image 1259120, www.forestryimages.org, May 23, 2004
- C Daniel Adam, Office National des Forêts, France, Image 2515023, www.invasive.org, Feb. 5, 2004
- D William M. Ciesla, Forest Health Management International, Image 0017003, www.invasive.org, Feb. 5, 2004
- E William M. Ciesla, Forest Health Management International, Image 0017006, www.invasive.org, Feb. 5, 2004
- F Jan Liska, Forestry and Game Management Research Institute, Czechia, Image 1191019, www.invasive.org, Feb. 5, 2004
- G Petr Kapitola, Forestry and Game Management Research Institute Czechia, Image 1191018, www.invasive.org, Feb. 5, 2004
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