- Who
- Wallace's sphinx moth, Xanthopan praedicta
- What
- 28.5 centimetre(s)
- Where
- Madagascar ()
- When
The longest tongue (proboscis) of any insect is that of Wallace's sphinx moth (Xanthopan praedicta), native to Madagascar. Its tongue measures up to 28.5 cm (11.2 in) – more than four times the length of the moth's body – which enables it to reach the nectar deep inside the star-shaped flowers of the comet orchid, aka Darwin's orchid (Angraecum sesquipedale).
For a long time, this Madagascan hawkmoth was regarded as a subspecies of the Morgan's sphinx moth, native to West Africa and the Comoros islands, and thus classified as Xanthopan morgani praedicta. However a study published in the September 2021 volume of Antenor set out multiple morphological differences that justify recognizing the Malagasy moth as its own species. The study was a collaboration between entomologists at the Muséum National d’Histoire Naturelle (France) and the UK's Natural History Museum, led by Professor Joël Minet.
According to the 2021 study, the average tongue length for the Wallace's sphinx moth is 21.97 cm (8.6 in) in females and 20.65 cm (8.1 in) in males. By comparison, in the Morgan's sphinx moth, proboscis length averaged 16.2 cm (6.4 in) in females and 13.4 cm (5.3 in) in males.
While 28.5 cm is the longest measured insect tongue, there's a good chance this species' proboscis can reach even greater lengths as the comet orchid's nectar tube can exceed 30 cm (11.8 in). What's more, a related orchid – Angraecum longicalar – has nectar tubes measuring up to 40 cm (1 ft 4 in), so there may be an as-yet-discovered moth species equipped with a tongue sufficiently long enough to reach its nectar, or there are even bigger specimens of Wallace's sphinx moth.
The specific name in its binomial ("praedicta") stems from the fact that the naturalists Charles Darwin and Alfred Russel Wallace both predicted that such a moth would exist after they studied the comet orchid, with its extremely elongated nectar tube. Wallace, whose name was adopted for the moth's common name, went as far to say in 1867: "That such a moth exists in Madagascar may be safely predicted, and naturalists who visit that island should search for it with as much confidence as astronomers searched for the planet Neptune, and they will be equally successful."
