Cephonodes xanthus 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...

 (Shikoku, Kyushu, Tanegashima, Tokara Island and the Ryukyu Archipelago).

It resembles Cephonodes janus janus

Cephonodes janus

Cephonodes janus is a moth of the Sphingidae family. It is known from Queensland, Flores and New Caledonia.The wingspan is about 50 mm. This species has a very narrow opaque margin around the wings, and a uniformly brown abdomen.-Subspecies:...

and Cephonodes trochilus

Cephonodes trochilus

Cephonodes trochilus is a moth of the Sphingidae family. It is known from Mauritius.The wingspan is 38-41 mm. It is very similar to Cephonodes tamsi, but distinguishable by the brownish rather than reddish upperside of the abdomen. The upperside of the head, thorax and wing bases are unicolorous...

in the unicolorous green upperside of the abdomen, and the latter especially in the somewhat deeper tint posteriorly. It is distinguishable from both by the broader forewing apical patch and the black abdominal tuft. The upperside of the abdomen is unicolorous green. The anal tuft is black and only the dorso-lateral scales are yellow. The underside of the head, thorax and abdomen are orange.