Acromyrmex coronatus

Acromyrmex coronatus
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Attini
Genus: Acromyrmex
Species: A. coronatus
Binomial name
Acromyrmex coronatus
Fabricius, 1804[1]

Acromyrmex coronatus is a New World ant of the subfamily Myrmicinae found in the wild naturally from Guatemala to Brazil and Ecuador. This species is from one of the two genera of advanced fungus-growing ants within the tribe Attini. Commonly known as "leaf-cutter ants", they are from one of the two genera: Acromyrmex can be identified from the closely related Atta genus of leafcutter ants by the four pairs of spines and rough exoskeleton on the upper surface of their thorax.

A mature A. coronatus colony contains mostly sterile female workers, divided into castes based mostly on size. Acromyrmex species exhibit a high degree of biological polymorphism, four castes being present in established colonies - minims (or "garden ants"), minors, mediae, and majors. Majors are also known as soldiers or dinergates. Each caste has a specific function within the colony. Acromyrmex ants are less polymorphic than the other genus of leafcutter ants, Atta, meaning comparatively less differential in size exists from the smallest to largest castes. The high degree of polymorphism in this genus is also suggestive of its high degree of advancement.

Like Atta, Acromyrmex subsists mostly on a particular species of fungus (genus Leucocoprinus), which it cultivates on a medium of masticated leaf tissue. This is the sole food of the queen and other colony members that remain in the nest. The mediae also gain subsistence from plant sap they ingest whilst physically cutting out sections of leaf from a variety of plants.

Before leaving their parent colonies, winged females take a small section of fungus into their bucchal pouches, with which the subsequently wingless queens 'seed' the fungus gardens of incipient colonies, cutting and collecting the first few sections of leaf themselves.

Acromyrmex has evolved to change food plants constantly, preventing a colony from completely stripping off leaves and thereby killing trees, thus avoiding negative biological feedback on account of their sheer numbers. However, this does not diminish the huge quantities of foliage they harvest.

A. coronatus can be identified by the presence of median pronotal spines being usually present and distinct, occasionally reduced or absent, the head tapering behind eyes, and head width of less than or equal to 1.7 mm.

This montane species is tolerant of cold, wet conditions, and colonies can be found in small clearings and gaps in dense cloud forest. For example, on the north side of Volcan Barva, it has been found at 1100 m elevation, but not at 500 or 2000 m. On the Central Valley side, it has been collected at 1600 m at Zurqui. In the Monteverde area, it occurs in the community area, up to the highest ridges at 1700 m, and down to 800 m in the Penas Blancas Valley.

In Monteverde, it is the main pest in gardens, and enters houses at night to cut bread, cabbage, or fruit that has been left out. The nests are often in or under a piece of dead wood, and often with a superstructure of loose, dead leaf fragments. They do not excavate soil very extensively, if at all. They may be arboreal at times, nesting in low branch junctions of epiphyte-laden trees.

A. coronatus foraging is continuous at night, but diurnal foraging only occurs after recent rain. Following a heavy rain, diurnal foraging commences, followed by a gradual cessation over a period of a day or two. Periodic rains during the dry season initiate a short bout of diurnal foraging, but when the rains became more continuous, diurnal foraging becomes continuous. Thus, the lack of diurnal foraging during the dry season is a short-term response to immediate environmental conditions and not a long-term change in colony foraging behavior.

Nuptial flights are common in Monteverde, and the distinctively patterned dealate queens are often seen on the roads. Dealate queens have been observed out cutting leaves, suggesting the queens need to forage themselves to establish a colony.

Subspecies

Synonyms

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References

  1. ↑ "Species: Acromyrmex coronatus". AntWeb. 2010-06-30. Retrieved 2010-08-20.
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