Theretra muricolor 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 Papua New Guinea

Papua New Guinea

Papua New Guinea , officially the Independent State of Papua New Guinea, is a country in Oceania, occupying the eastern half of the island of New Guinea and numerous offshore islands...

.

It is very similar to Theretra queenslandi

Theretra queenslandi

Theretra queenslandi is a moth of the Sphingidae family. It is known from New South Wales and Queensland.The wingspan is about 60 mm. Adults have light brown forewings with a dark stripe running from the base to the apex. There is a dark dot near the middle of the costa. The hindwings are darker...

but smaller and the forewing ground colour is pale grey. The forewing upperside is as in Theretra queenslandi, but the ground colour is pale silvery-grey. Consequently, the dark discal spot is much more conspicuous. The hindwing upperside is also as in Theretra queenslandi, but the paler marginal area is broader.