Xanthopan morganii

Life-forms

Superregnum: Eukaryota
Cladus: Unikonta
Cladus: Opisthokonta
Cladus: Holozoa
Regnum: Animalia
Subregnum: Eumetazoa
Cladus: Bilateria
Cladus: Nephrozoa
Cladus: Protostomia
Cladus: Ecdysozoa
Cladus: Panarthropoda
Phylum: Arthropoda
Subphylum: Hexapoda
Classis: Insecta
Cladus: Dicondylia
Subclassis: Pterygota
Cladus: Metapterygota
Infraclassis: Neoptera
Cladus: Eumetabola
Cladus: Endopterygota
Superordo: Panorpida
Cladus: Amphiesmenoptera
Ordo: Lepidoptera
Subordo: Glossata
Cladus: Coelolepida
Cladus: Myoglossata
Cladus: Neolepidoptera
Infraordo: Heteroneura
Cladus: Eulepidoptera
Cladus: Ditrysia
Cladus: Apoditrysia
Cladus: Obtectomera
Cladus: Macroheterocera
Superfamilia: Bombycoidea

Familia:Sphingidae
Subfamilia: Sphinginae
Tribus: Sphingini
Genus: Xanthopan
Species: X. morganii

Xanthopan morganii (often misspelled as "morgani"),[1] is a sphinx moth, commonly called Morgan's sphinx moth, as its sole species. It is a very large sphinx moth from Southern Africa (Zimbabwe, Zambia, Malawi) and Madagascar. Little is known about its biology, though the adults have been found to visit orchids and are one of the main pollinators of several of the Madagascar endemic baobab (Adansonia) species,[2] including the critically endangered[3] Adansonia perrieri or Perrier's baobab.
Overview
In 1867 Alfred Russel Wallace made predictions supporting Darwin's surmise.[4]

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"[?][7] The spur of the flower is 20–35 cm (7.9–13.8 in) from its tip to the tip of the flower's lip. The name "sesquipedale" is Latin for "one and a half feet," referring to the spur length.

From his observations and experiments with pushing a probe into the spur of the flower, Darwin surmised in his 1862 book Fertilisation of Orchids that there must be a pollinator moth with a proboscis long enough to reach the nectar at the end of the spur.[8] In its attempt to get the nectar at the end of the spur the moth would get pollen rubbed off on its head. The next orchid it visited would then be pollinated in the same manner.[4]

In 1867 Alfred Russel Wallace published an article in which he supported Darwin's hypothesis, remarking that the African sphinx moth Xanthopan morganii (then known as Macrosila morganii) had a proboscis almost long enough to reach the bottom of the spur. In a footnote to this article Wallace wrote "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!"[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 & Karl Jordan, in honour of Wallace's (not Darwin's) prediction. Darwin's earlier, but less specific, prediction was not even mentioned by them.[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. Molecular clock models using either rate- or fossil-based calibrations imply that the Madagascan subspecies X. morganii praedicta and the African subspecies X. morganii morganii diverged 7.4 ± 2.8 Mya, which overlaps the divergence of A. sesquipedale from its sister, A. sororium, namely 7.5 ± 5.2 Mya.[12] Since both these orchids have extremely long spurs, long spurs likely existed before that and were exploited by long-tongued moths similar to Xanthopan morganii praedicta. The long geological separation of the subspecies morganii and praedicta matches their morphological differences in the colour of breast and abdomen.

Morgan's sphinx moth approaches the flower to ascertain by scent whether or not it is the correct orchid species. Then the moth backs up over a foot and unrolls its proboscis, then flies forward, inserting it into the orchid's spur.[13]

The larvae feed on Annona senegalensis, Hexalobus crispiflorus, Uvaria, Ibaria and Xylopia species.[14]
References

Walker, F. (1856). List of the Specimens of Lepidopterous Insects in the Collection of the British Museum. 8: 206.
Baum, D. A. (1995). "A Systematic Revision of Adansonia (Bombacaceae)". Annals of the Missouri Botanical Garden. 82 (3): 440-471.
Letsara, R.; Faranirina, L.; Razafindrahaja, V. & Faramalala, M. (2019). "Adansonia rubrostipa". The IUCN Red List of Threatened Species 2019: e.T37679A64366919. https://dx.doi.org/10.2305/IUCN.UK.2019-3.RLTS.T37679A64366919.en. Retrieved 8 July 2020.
Kritsky, Gene (1991). "Darwin's Madagascan Hawk Moth prediction" (PDF). American Entomologist. Vol. 37. pp. 206–9. Archived from the original (PDF) on February 29, 2012. Retrieved 2009-02-09.
"Darwin Correspondence Project - Letter 3357 — Bateman, Robert to Darwin, C. R., (1862)". Retrieved 2009-02-09.
"Darwin Correspondence Project - Letter 3356 — Bateman, James to Darwin, C.R., (1862)". Retrieved 2009-02-09.
"Darwin Correspondence Project - Letter 3411 — Darwin, C. R. to Hooker, J. D., 25 Jan (1862)". Retrieved 2009-02-09.
Darwin 1862, pp. 197–203
Wallace, Alfred R. (1867). "Creation by Law". The Quarterly Journal of Science: 477. Retrieved 2016-05-20.
Rothschild, W.; Jordan, K. (1903). "A revision of the Lepidopterous family Sphingidae". Novitates Zoologicae. 9 (Supplement): 32.
Beccaloni, George (2010). "Darwin and Wallace's Predictions Come True". Retrieved 2015-07-01.
Netz, Christoph; Renner, Susanne S. (2017). "Long-spurred Angraecum orchids and long-tongued sphingid moths on Madagascar: A time-frame for Darwin's predicted Xanthopan/Angraecum coevolution". Biological Journal of the Linnean Society. 122 (Supplement): 469–478. doi:10.1093/biolinnean/blx086.
Wasserthal, L.T. (1997). The pollinators of the Malagasy star orchids Angraecum sesquipedale, A. sororium and A. compactum and the evolution of extremely long spurs by pollinator shift. Botanica Acta 110: 343–359

De Prins, J. & De Prins, W. (2018). "Xanthopan morganii morganii (Walker, 1856)". Afromoths. Retrieved 2017-07-26.

Darwin, Charles (1862). On the Various Contrivances by Which British and Foreign Orchids Are Fertilised by Insects, and On the Good Effects of Intercrossing. London: John Murray. Retrieved 2009-02-07.