(Ocneria, or Porthetria, monacha), a moth of the family Lymantriidae; a dangerous forest pest. The wingspread is 35–55 mm. The fore wings are white with black, serrated, transverse lines; the hind wings are whitish gray.
The nun moth is widely distributed in the forest zone of Europe and Asia (northward to 58° N lat.). It damages many varieties of trees, particularly spruce, pine, larch, beech, oak, and hornbeam. There is one generation per year. The moths emerge beginning in the second half of July; they deposit from 300 to 500 eggs in small mounds in the cracks of tree bark. In three or four weeks the caterpillars develop; they hibernate and emerge from their cocoons in late April or in May. The caterpillars chew needles and leaves and eat pollen, buds, and young shoots; later they are able to feed on old needles. They pupate in loose cobwebs among leaves and in crevices. The nun moth has periods of massive reproduction that last seven or eight years. The most frequent and largest occurrences of massive reproduction are observed in the Volga Region, the Middle and Southern Urals, and Western Siberia. Nun moths are destroyed by entomophagous organisms. Massive reproduction periods of nun moths are often suppressed by such caterpillar diseases as flacherie and polyhedrosis.
P. A. POLOZHENTSEV