Theretra cajus 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 South Africa

South Africa

The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...

 and Zimbabwe

Zimbabwe

Zimbabwe is a landlocked country located in the southern part of the African continent, between the Zambezi and Limpopo rivers. It is bordered by South Africa to the south, Botswana to the southwest, Zambia and a tip of Namibia to the northwest and Mozambique to the east. Zimbabwe has three...

.

The abdomen upperside has two strong white longitudinal lines, which are fused at the anterior and posterior margins of each segment, giving the appearance of a chain. The forewing upperside has a dark brown band running between the first and third postmedian lines and fifth postmedian line, contrasting very strongly with the almost white intervening band. A distinct discal line is present, with another line proximal to it but generally lost in the brown discal area. The submarginal line is distinct in most specimens and the marginal band shaded with grey.