Myrmecophagy

The snout and the scientific name of the giant anteater (Myrmecophaga tridactyla) reflect its feeding habits.

Myrmecophagy is a feeding behavior defined by the consumption of termites or ants, particularly as pertaining to those animal species whose diets are largely or exclusively composed of said insect types. Literally, myrmecophagy means "ant eating" (Ancient Greek: murmēx, "ants" and phagein, "to eat") rather than "termite eating" (for which the strict term is termitophagy). However, the two habits often overlap, as both of these eusocial insect types often live in large, densely populated nests requiring similar adaptations in the animal species that exploit them.^[1]

Myrmecophagy in vertebrates

Myrmecophagy is found in a number of land-dwelling vertebrate taxa, including reptiles and amphibians (horned lizards and blind snakes, narrow-mouthed toads of the family Microhylidae and poison frogs of the Dendrobatidae), a number of New World bird species (Antbirds, Antthrushes, Antpittas, flickers of genus Colaptes), and several mammalian groups (anteaters, aardvarks, aardwolves, pangolins, sloth bears, and many armadillos, numbats and echidnas, for instance).

Myrmecophagous mammals are very prominent examples of convergent evolution. Almost all of the aforementioned otherwise unrelated mammals that specialize in myrmecophagy often display similar adaptations for this niche. Many have powerful forelimbs and claws adapted to excavating the nests of ant or termite colonies from the earth or from wood or under bark. Most have reduced teeth and some have reduced jaws as well. Practically all have long, sticky tongues. In the nineteenth and early twentieth century many zoologists saw these shared features as evidence of relatedness, and accordingly they regarded the various species as single order of Mammalia, the Edentata. However it quite early became clear that such a classification was hard to sustain, and there was a growing trend to see the features as examples of convergent evolution. For example, at the start of the 20th century Frank Evers Beddard, writing in The Cambridge Natural History, Vol 10, Mammalia, having discussed some discrepant features, said: "The fact is, that we have here a polymorphic order which contains in all probability representatives of at least two separate orders. We have at present a very few, and these perhaps highly modified, descendants of a large and diverse group of mammals."^[2]

Myrmecophagy in invertebrates

Generally speaking, ants are little fed upon because they tend to be dangerous, small, and rich in harmful compounds, so much so that ant mimicry is a common strategy of defence among invertebrates. However, ants also are plentiful, so members of several invertebrate taxa do feed on ants. Such ant predators include some spiders, such as species in the family Salticidae (jumping spiders), and spiders in the family Oecobiidae. Some spiders, including some myrmecomorphs (ant mimics) and myrmecophiles even specialise in ants as prey. Myrmecomorphs are Batesian mimics. They gain protection against predators, and abundant food.^[3]

Various species of the Hemipteran suborder Heteroptera, in the family Reduviidae feed largely or exclusively on ants. Examples include the genera Paredocla and Acanthaspis^[4]

Some insects that feed on ants do so because they are opportunistic predators of small insects that run on the ground surface, of which ants are a large proportion. Remarkable examples of convergent evolution are certain species of the Neuropteran family Myrmeleontidae, largely Myrmeleon, the so-called ant lions, and the Dipteran family Vermileonidae, in particular the genera Lampromyia and Vermilio, the so-called worm lions. Both of them are regarded with interest for their habit of constructing conical pit traps in fine sand or dust, at the bottom of which they await prey that has fallen in. Both throw sand to interfere with any attempts on the part of the prey to escape.^[5]

Myrmecophagy takes more forms than just eating adult ants; the later instars of caterpillars of many butterflies in the family Lycaenidae enter the nests of particular species of ants and eat the ants' eggs and larvae.^[6] Larvae of some species of flies, such as the genus Microdon in the family Syrphidae spend their entire immature lives in the nests of ants, feeding largely or entirely on the ant brood. Some beetles specialise in feeding on the brood of particular species of ants. An example is the coccinellid Diomus; larvae of Diomus thoracicus in French Guiana specialise in the nests of the invasive ant species Wasmannia auropunctata.^[7]

One of the predominate predators on ants are other ants, especially the army ants and their close relatives.^[8][9] Some ants such as the raider ant Cerapachys biroi and the new world army ant Nomamyrmex esenbecki are obligate myrmecophages, that is they eat exclusively other ants,^[9][10] while other ants like the infamous swarm-raiding Eciton burchellii eat more or less all arthropods in their paths, including any ants they can get.^[8][9] Primarily it is the highly nutritious pupae and larvae, rather than the adult ants, that are taken and eaten.^[8][9]

References

1. Crompton, John (1954). Ways of the Ant. Collins. ISBN 9780941130844.
2. Beddard, Frank Evers (1902). Harmer, Sir Sidney Frederic; Shipley, Arthur Everett; Gadow, Hans, eds. Mammalia. The Cambridge Natural History. 10. Macmillan Company.
3. Cushing, Paula E. (2012). "Spider-Ant Associations: An Updated Review of Myrmecomorphy, Myrmecophily, and Myrmecophagy in Spiders". Psyche. 2012: Article ID 151989. doi:10.1155/2012/151989.
4. Brandt, Miriam; Mahsberg, Dieter (February 2002). "Bugs with a backpack: the function of nymphal camouflage in the West African assassin bugs Paredocla and Acanthaspis spp.". Animal Behaviour. 63 (2): 277–284. doi:10.1006/anbe.2001.1910.
5. Wilson, Edward O. (2000). Sociobiology: the new synthesis. Harvard University Press. pp. 172–. ISBN 978-0-674-00089-6. Retrieved 24 May 2013.
6. Ballmer, Gregory R.; Pratt, Gordon F. (1988). A Survey of the Last Instar Larvae of the Lycaenidae (Lepidoptera) of California. Retrieved 25 May 2013.
7. Vantaux, Amélie; Roux, Olivier; Magro, Alexandra; Ghomsi, Nathan Tene; Gordon, Robert D.; Dejean, Alain; Orivel, Jérôme (September 2010) [13 January 2010]. "Host-Specific Myrmecophily and Myrmecophagy in the Tropical Coccinellid Diomus thoracicus in French Guiana". Biotropica. 42: 622–629. doi:10.1111/j.1744-7429.2009.00614.x.
8. Gotwald, William (1995). Army Ants: the Biology of Social Predation. Comstock Publishing Associates. ISBN 0801426332.
9. Hölldobler, Bert; Wilson, Edward O. (1990). The Ants. Belknap Press of Harvard University Press. ISBN 0-674-04075-9.
10. Powell, Scott; Clark, Ellie (1 November 2004). "Combat between large derived societies: a subterranean army ant established as a predator of mature leaf-cutting ant colonies". Insectes Sociaux. 51 (4): 342–351. doi:10.1007/s00040-004-0752-2.