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Saturnia pyretorum Westwood, 1847 四黑目天蠶蛾

Tags: insect | moth


Saturnia pyretorum Westwood, 1847 四黑目天蠶蛾

The Giant Silkworm Saturnia pyretorum has economic significance in terms of silk production. The moth is also known as Fish-line Silkworm because its silk is used to make into natural fish-lines. The indigenous range of the species may include India, Vietnam and southern China but is hard to determine because of a long artificial-breeding history of the moths (as early as 885 AC). The adults have a wingspan of 75~85 mm in males and 105~110 mm in females. The wing coloration is grayish brown, featured with several wavy bands and two pairs of black eye spots in equal size on the forewings and hindwings.
The Giant Silkworm is univoltine. The female moths cover their eggs with shed hairs. Young larvae hatched after three weeks of egg stage. There are seven to eight larval instars. They feed mainly on Liquidambar formosana Hance (Hamamelidaceae) and Cinnamomum camphora (L.) Sieb (Lauraceae), and occasionally become minor pest to the host plants. The larvae are green in ground coloration, featured with noticeable blue and yellow longitudinal lines. Their bodies bear many long hairs but are harmless to people. The larvae grow fast into mature in about three weeks. They pupate within silk cocoons attached to tree trunks or branches, and oversummer as pupae. The adults appear in the winter.

The species was introduced to Taiwan for economic purpose during the Japanese colonization in the first half of the 20 century. Moth farms were built in central Taiwan to produce silk fishing lines for export. The moths have spread into the wildness after the moth farms were shut down in 1950. They are now a naturalized species in Taiwan and have natural populations in the field. The moth in Taiwan was once reported as Eriogyna pyretorum pearsoni Watson, a subspecies originally described from Hainan Island, southern China. Yet the Eriogyna has been rendered as a junior synonym or a subgenus of Saturnia and the differentiation of subspecies is considered unnecessary. So the name Saturnia pyretorum was used herein. 

National Museum of Natural Science (The Digital Museum of Nature & Culture