Hippotion geryon 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 Madagascar

Madagascar

The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...

 and the Comoro Islands

Comoro Islands

The Comoros Islands form an archipelago of volcanic islands situated off the south-east coast of Africa, to the east of Mozambique and north-west of Madagascar. They are divided between the sovereign state of Comoros and the French overseas department of Mayotte...

.

It is similar to Hippotion osiris

Hippotion osiris

Hippotion osiris is a moth of the Sphingidae family. It is common throughout most of the Ethiopian Region, including Madagascar and the Seychelles. Occasional vagrants have been recorded from Spain. It is uncommon on the East African coast. This species is an occasional migrant.The length of the...

, but is immediately distinguishable by the lack of pink coloration on the hindwing upperside and the single pair of black abdominal patches. The upperside of the antennae is conspicuously pink-scaled. The base of the abdomen has a single pair of large, square, black subdorsal patches. The forewing upperside is very similar to Hippotion osiris but differing in the distal part of the longitudinal pale band through the discal cell being absent beyond the discal spot. The hindwing upperside is dark brown with a buff patch on the inner margin and a buff postmedian band.