Isognathus occidentalis 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 Venezuela

Venezuela

Venezuela , officially called the Bolivarian Republic of Venezuela , is a tropical country on the northern coast of South America. It borders Colombia to the west, Guyana to the east, and Brazil to the south...

, northern Brazil

Brazil

Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...

 and French Guiana

French Guiana

French Guiana is an overseas region of France, consisting of a single overseas department located on the northern Atlantic coast of South America. It has borders with two nations, Brazil to the east and south, and Suriname to the west...

.

It is similar to Isognathus excelsior

Isognathus excelsior

Isognathus excelsior is a moth of the Sphingidae family. It is known from Colombia, Venezuela and Ecuador to north-western Brazil.It can be distinguished from all other Isognathus species by the pure white underside to the abdomen with conspicuous paired black spots on each segment.There are...

but distinguishable by the pale brown underside of the abdomen. There are probably multiple generations per year.

The larvae have been recorded feeding on Himatanthus lancifolius. They have long tails and very colourful, suggesting they are unpalatable to birds.