Samia cynthia

(Drury, 1773)

ailanthus silkmoth, eri silkmoth

Samia cynthia is a large saturniid used for silk production, though less domesticated than Bombyx mori. have wingspans of 113–125 mm with distinctive quarter-moon shaped spots on both wing surfaces, whitish and yellow stripes on a brown background, and eyespots on the outer forewings. The is native to East Asia and has been introduced to multiple continents, often escaping from . The S. c. ricini, known as the eri silkmoth, feeds on castor bean and produces durable eri silk that must be spun rather than reeled.

Samia cynthia by (c) Takaaki Hattori, some rights reserved (CC BY), uploaded by Takaaki Hattori. Used under a CC-BY license.

Samia cynthia 0zz by Photo by David J. Stang. Used under a CC BY-SA 4.0 license.

Samia cynthia pryeri 115312612 by heikindai_87. Used under a CC0 license.

Pronunciation

How to pronounce Samia cynthia: //ˈseɪ.mi.ə ˈsɪn.θi.ə//

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

Distinguished by very large wings (113–125 mm wingspan) with quarter-moon shaped spots present on both upper and lower wing surfaces. Forewings bear eyespots on the outer margins. Coloration consists of whitish and yellow longitudinal stripes against a brown background. lack functional mouthparts. Larvae are yellow in early instars, becoming whitish green with white and small black dots in later instars; mature larvae reach 70–75 mm.

Images

Habitat

Associated with plant Ailanthus altissima (tree of heaven), commonly found in urban ornamental plantings. Thrives on this tree , which is considered a noxious weed in Europe and North America. The S. c. ricini occurs in India and Thailand in association with castor bean .

Distribution

Native to East Asia: China (Zhejiang, Shanghai, Jiangxi, Jiangsu, Shandong, Beijing, Shanxi, Liaoning, Heilongjiang provinces) and Korea (North Pyongan, South Pyongan, Pyongyang, Kangwon, South Kyongsan, Chungcheongnam-do provinces). Introduced and naturalized in Japan, India, Philippines, Thailand, Australia, Canada, United States, Venezuela, Uruguay, Brazil, Tunisia, France, Austria, Switzerland, Germany, Spain, Bulgaria, and Italy.

Seasonality

In northern Europe, fly during May and June as a single . In southern Europe, a partial second generation may occur in September. Females emerge in late morning and prepare to mate in the evening or night of the same day.

Diet

Larvae feed primarily on Ailanthus altissima (tree of heaven), on which growth is optimal. All are laid on this despite larvae being capable of feeding on other trees and shrubs. The S. c. ricini feeds specifically on castor bean (Ricinus communis). lack mouthparts and do not feed.

Host Associations

Ailanthus altissima - primary plantAll laid on this ; optimal larval growth
Ricinus communis - plantPrimary for S. c. ricini

Life Cycle

Complete with four stages. are whitish with brown markings, laid in rows of 10–20 in crescent patterns on leaves; hatch in 7–10 days. Larvae pass through five instars, with early instars gregarious and yellow, later instars solitary and whitish green with white and black dots. Larvae reach 70–75 mm at maturity. occurs in an off-white to grey silken cocoon spun on leaves, featuring an obvious escape hatch. emerge and reproduce without feeding due to absent mouthparts.

Behavior

Larvae exhibit ontogenetic shift in social : early instars are gregarious, later instars become solitary. females prepare to mate on the evening or night of their day. activity is seasonal and geographically variable.

Ecological Role

Larval herbivore on Ailanthus altissima, an aggressive plant in Europe and North America; may contribute to of this weed. Serves as for including tangle-veined flies (Nemestrinidae). Pupae are consumed as food in some cultures.

Human Relevance

Source of eri silk from the S. c. ricini; the only completely domesticated besides Bombyx mori. Eri silk is extremely durable but cannot be reeled, requiring spinning like cotton or wool. Silk used in traditional textiles including Assamese chaddars. has been introduced globally through and has established .

Similar Taxa

Bombyx moriAlso a silk-producing , but fully domesticated with smaller size, different wing pattern lacking quarter-moon spots, and dependent on Morus (mulberry) rather than Ailanthus
Samia cynthia ricini with similar but distinct association (castor bean vs. tree of heaven) and complete domestication for eri silk production
Antheraea pernyiAnother wild silk (tussah) with different wing pattern, plants, and silk characteristics