Samia cynthia

(Drury, 1773)

ailanthus silkmoth, eri silkmoth

Samia cynthia is a large used for production, though less domesticated than Bombyx mori. have wingspans of 113–125 mm with distinctive quarter-moon shaped spots on both surfaces, whitish and stripes on a background, and on the outer . The is to East Asia and has been to multiple continents, often escaping from . The S. c. ricini, known as the eri , 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 (113–125 mm wingspan) with quarter-moon shaped spots present on both upper and lower wing surfaces. bear on the outer margins. Coloration consists of whitish and longitudinal stripes against a background. lack functional mouthparts. are yellow in early , becoming whitish green with and small black dots in later instars; mature larvae reach 70–75 mm.

Images

Habitat

Associated with 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

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). 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, 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

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 All laid on this ; optimal larval growth
Ricinus communis - Primary for S. c. ricini

Life Cycle

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

Behavior

exhibit ontogenetic shift in social : early 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 on Ailanthus altissima, an aggressive in Europe and North America; may contribute to of this weed. Serves as for including (). are consumed as food in some cultures.

Human Relevance

Source of eri 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 globally through and has established .

Similar Taxa

Bombyx moriAlso a -producing , but fully domesticated with smaller size, different 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 production
Antheraea pernyiAnother wild (tussah) with different pattern, plants, and silk characteristics