In January 1862 while researching insect pollination of orchids, Charles Darwin received a package of orchids from the distinguished horticulturist James Bateman, and in a follow-up letter with a second package Bateman's son Robert confirmed the names of the specimens, including Angraecum sesquipedale from Madagascar.

[5][6] Darwin was surprised at the defining characteristic of this species: the "astonishing length" of the whip-like green spur forming the nectary of each flower, and remarked to Joseph Hooker "I have just received such a Box full from Mr Bateman with the astounding Angræcum sesquipedalia with a nectary a foot long—Good Heavens what insect can suck it"[?

"[9] Subsequently, the sphingid experts Walter Rothschild and Karl Jordan received one male and one female specimen of Xanthopan morganii (commonly called Morgan's sphinx moth) with an especially long proboscis, collected on Madagascar by Charles Oberthür and Paul Mabille.

Since Wallace predicted that the mystery pollinator would turn out to be a sphinx moth, rather than simply a large moth as Darwin had suggested, the Madagascan form was named subspecies praedicta by Walter Rothschild and Karl Jordan, in honour of Wallace's (not Darwin's) prediction.

[10][11] The Madagascan subspecies is known as Wallace's sphinx moth and it differs from the African form by having a pink, rather than white, breast and abdomen and a black apical line on the forewing, which is broader than in mainland specimens.

The long geological separation of the subspecies morganii and praedicta matches their morphological differences in the colour of breast and abdomen.

Some species, such as Wallace's sphinx moth (X. m. praedicta), are capable of producing ultrasonic sounds to deter bat predation.