Rhagastis trilineata is a moth

Moth

A moth is an insect closely related to the butterfly, both being of the order Lepidoptera. Moths form the majority of this order; there are thought to be 150,000 to 250,000 different species of moth , with thousands of species yet to be described...

 of the Sphingidae

Sphingidae

Sphingidae is a family of moths , commonly known as hawk moths, sphinx moths and hornworms, that includes about 1,200 species . It is best represented in the tropics but there are species in every region . They are moderate to large in size and are distinguished among moths for their rapid,...

 family. It is known from Japan

Japan

Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

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It is similar to Rhagastis mongoliana

Rhagastis mongoliana

Rhagastis mongoliana is a moth of the Sphingidae family. It is found from China, north to Mongolia, Korea and the Primorsky Krai in Russia, and east to Taiwan and Japan.The wingspan is 47-63 mm...

but distinguishable by the almost uniform (not distinctly chequered) forewing fringes and the small black discal spot on the hindwing underside. The hindwing underside has a small black discal spot.

Larvae have been recorded feeding on Hydrangea macrophylla

Hydrangea macrophylla

Hydrangea macrophylla is a species of Hydrangea native to Japan. Common names include Bigleaf Hydrangea, French Hydrangea, Lacecap Hydrangea, Mophead Hydrangea, Penny Mac and Hortensia...

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