The Info List - Acromyrmex

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is a genus of New World
New World
ants of the subfamily Myrmicinae. This genus is found in South America
South America
and parts of Central America
Central America
and the Caribbean Islands, and contains 31 known species. Commonly known as "leafcutter ants" they comprise one of the two genera of advanced attines within the tribe Attini, along with Atta.


1 Anatomy 2 Ecology

2.1 Reproduction 2.2 Colony hierarchy 2.3 Ant-fungus mutualism 2.4 Waste management 2.5 Foraging behaviour

3 Interactions with humans 4 Species 5 See also 6 References 7 External links


Profile view of an A. balzani worker

species' hard outer covering, the exoskeleton or cuticle, functions as armour, protection against dangerous solar waves, an attachment base for internal muscles, and to prevent water loss. It is divided into three main parts; the head, thorax, and abdomen. A small segment between the thorax and abdomen, the petiole, is split into two nodes in Acromyrmex

Diagram of an ant's anatomy

The antennae are the most important sense organs Acromyrmex
species possess, and are jointed so the ant can extend them forward to investigate an object. It can retract them back over its head when in a dangerous situation, for example, a fight. Acromyrmex
species have eyes, but their eyesight is very poor. Like all insects, the eye is compound, meaning it is made up of many eyelets called ommatidia, with the number of these eyelets varies according to species. Male ants tend to have more ommatadia than other castes. The ocelli, which are generally found on top of the heads of queens, are thought to aid aerial navigation by sunlight. Acromyrmex
is dark red in color. In addition to the standard ant anatomy, the back of the thorax has a series of spines which help it maneuver material such as leaf fragments on its back. Acromyrmex
can be identified from the closely related Atta genus of leafcutter ants by their having four pairs of spines and a rough exoskeleton on the upper surface of the thorax compared to three pairs of spines and a smooth exoskeleton in Atta. Much of the inside of the Acromyrmex
head is occupied by the muscles that close the jaws; the muscles that open the jaws are much smaller. The brain, though tiny, is a very complex organ, and allows Acromyrmex to learn and react to its surroundings. It can remember colony odour, navigation, and where it has placed a certain object. The heart is a long, tubular organ running the entire length of the body, from the brain to the tip of the abdomen. It has valves within it that prevent blood from flowing the wrong way. The fluids bathing the internal organs is circulated by the heart; these fluids then filter through the organs and tissues. The pharynx, which is part of the gut, controlled by six muscles, pumps food into the oesophagus. Debris in the food, such as soil, is filtered before it enters the oesophagus and is collected in a tiny trap, the infrabuccal pocket. When this pocket becomes full, the Acromyrmex
ant empties it into an area within or outside the nest designated as a waste-products area. Several glands in the head secrete various substances, such as those responsible for the digestion of food. Another gland within the head produces digestive and, in some species, alarm chemicals; these chemicals are used to alert nearby ants of impending danger, and any ant that detects this alarm will automatically go into "battle mode". If an ant is crushed, a huge blast of this chemical is released, causing the entire colony to go into "battle mode". The thorax contains muscles to operate the legs and wings and the nerve cells to co-ordinate their movements; also contained in this part of the body is the heart and oesophagus. The abdomen contains the stomachs, poison glands, ovaries in the queen, and the Dufour's gland, among other things. Acromyrmex
ants have two "stomachs", including a dry, social stomach in which they can store food and later regurgitate to larvae, the queen and other ants. This is separated from the stomach proper by a small valve; once food enters the second stomach, it becomes contaminated with gastric juices and cannot be regurgitated. The exact function of the Dufour's gland is unknown, but is thought to be involved in the release of the chemicals used in the production of odour trails, which the ants use to recruit nest mates to a food source. It may also produce sex-attractant chemicals. Ecology[edit]

A. balzani worker carrying a leaf

Reproduction[edit] Winged females and males leave their respective nests en masse and engage in a nuptial flight known as the revoada. Each female mates with multiple males to collect the 300 million sperm she needs to set up a colony.[2] Once on the ground, the female loses her wings and searches for a suitable underground lair in which to found her colony. The success rate of these young queens is very low and only 2.5% will go on to establish a long-lived colony. Before leaving their parent colonies, winged females take a small section of fungus into their infrabucchal pouches to 'seed' the fungus gardens of incipient colonies, cutting and collecting the first few sections of leaf themselves. Colony hierarchy[edit] A mature leafcutter colony can contain more than 8 million ants (the maximum size of the colony varies between species), mostly sterile female workers. They are divided into castes, based mostly on size, that perform different functions. Acromyrmex
ants 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 difference in size exists from the smallest to largest types of Acromymex. The high degree of polymorphism in this genus is also suggestive of its high degree of advancement. Ant-fungus mutualism[edit] Like Atta, Acromyrmex
societies are based on an ant-fungus mutualism, and different species use different species of fungus, but all of the fungi the ants use are members of the genus Leucocoprinus. The ants actively cultivate their fungus 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. This mutualistic relationship is further augmented by another symbiotic partner, a bacterium that grows on the ants and secretes chemicals; essentially, the ants use portable antimicrobials. Leafcutter ants
Leafcutter ants
are sensitive enough to adapt to the fungus' reaction to different plant material, apparently detecting chemical signals from it. If a particular type of leaf is toxic to the fungus, the colony will no longer collect it. The only two other groups of insects that have evolved fungus-based agriculture are ambrosia beetles and termites. The fungus cultivated by the adults is used to feed the ant larvae and the adult ants feed on the leaf sap. The fungus needs the ants to stay alive, and the larvae need the fungus to stay alive.[3] In addition to feeding the fungal garden with foraged food, mainly consisting of leaves, it is protected from Escovopsis by the antibiotic secretions of Actinobacteria
(genus Pseudonocardia). This mutualistic microorganism lives in the metapleural glands of the ants.[4] Actinobacteria
are responsible for producing the majority of the world's antibiotics today. Waste management[edit] Leafcutter ants
Leafcutter ants
have very specific roles for taking care of the fungal garden and dumping the refuse. Waste management is a key role for each colony's longevity. The necrotrophic parasite Escovopsis of the fungal cultivar threatens the ants' food source, and is a constant danger to the ants. The waste transporters and waste-heap workers are the older, more dispensable ants, ensuring the healthier and younger leafcutter ants can work on the fungal garden. Waste transporters take the waste, which consists of used substrate and discarded fungus, to the waste heap. Once dropped off at the refuse dump, heap workers organise the waste and constantly shuffle it around to aid decomposition. Foraging behaviour[edit]

Leafcutter ants
Leafcutter ants
in Costa Rica

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. Once foraging workers locate a resource in their environment, they lay down a pheromone trail as they return to the colony. Other workers then follow the pheromone trail to the resource. As more workers return to the nest, laying down pheremones, the stronger the trail becomes. The strength to which workers adhere to the trail (trail fidelity) depends mostly on environmental factors, such as the quality of the resource. Interactions with humans[edit] In some parts of their range, Acromyrmex
species can be quite a nuisance to humans, defoliating crops and damaging roads and farmland with their nest-making activities.[2] For example, Acromyrmex octospinosus ants harvest huge quantities of foliage, so they have become agricultural pests on the various Caribbean islands where they have been introduced, such as Guadeloupe. In Central America, leafcutter ants are referred to as "wee wee" ants, though not based on their size. They are one of the largest ants in Central America.[citation needed] Deterring the leafcutter ant Acromyrmex lobicornis
Acromyrmex lobicornis
from defoliating crops has been found to be simpler than first expected. Collecting the refuse from the nest and placing it over seedlings or around crops resulted in a deterrent effect over a period of 30 days.[5] Species[edit] The genus Acromyrmex
contains 32 species:[1]

Acromyrmex ambiguus Emery, 1888 Acromyrmex ameliae De Souza, Soares & Della Lucia, 2007 Acromyrmex aspersus F. Smith, 1858 Acromyrmex balzani
Acromyrmex balzani
Emery, 1890 Acromyrmex biscutatus Fabricius, 1775 Acromyrmex coronatus
Acromyrmex coronatus
Fabricius, 1804 Acromyrmex crassispinus
Acromyrmex crassispinus
Forel, 1909 Acromyrmex diasi Gonçalves, 1983 Acromyrmex disciger Mayr, 1887 Acromyrmex echinatior Forel, 1899 Acromyrmex evenkul Bolton, 1995 Acromyrmex fracticornis
Acromyrmex fracticornis
Forel, 1909 Acromyrmex heyeri
Acromyrmex heyeri
Forel, 1899 Acromyrmex hispidus Santschi, 1925 Acromyrmex hystrix Latreille, 1802 Acromyrmex insinuator
Acromyrmex insinuator
Schultz, Bekkevold & Boomsma, 1998 Acromyrmex landolti Forel, 1885 Acromyrmex laticeps Emery, 1905 Acromyrmex lobicornis
Acromyrmex lobicornis
Emery, 1888 Acromyrmex lundii
Acromyrmex lundii
Guérin-Méneville, 1838 Acromyrmex niger
Acromyrmex niger
F. Smith, 1858 Acromyrmex nigrosetosus
Acromyrmex nigrosetosus
Forel, 1908 Acromyrmex nobilis Santschi, 1939 Acromyrmex octospinosus
Acromyrmex octospinosus
Reich, 1793 Acromyrmex pubescens Emery, 1905 Acromyrmex pulvereus Santschi, 1919 Acromyrmex rugosus
Acromyrmex rugosus
F. Smith, 1858 Acromyrmex silvestrii Emery, 1905 Acromyrmex striatus
Acromyrmex striatus
Roger, 1863 Acromyrmex subterraneus
Acromyrmex subterraneus
Forel, 1893 Acromyrmex versicolor
Acromyrmex versicolor
Pergande, 1894 Acromyrmex volcanus Wheeler, 1937

See also[edit]

List of leafcutter ants Leafcutter ants


^ a b Bolton, B. (2014). "Acromyrmex". AntCat. Retrieved 20 July 2014.  ^ a b Piper, Ross (2007), Extraordinary Animals: An Encyclopedia of Curious and Unusual Animals, Greenwood Press, p. 298, ISBN 0-313-33922-8 . ^ "Archived copy". Archived from the original on 2012-02-02. Retrieved 2012-01-30.  ^ Zhang, M. M.; Poulsen, M. & Currie, C. R. (2007), "Symbiont recognition of mutualistic bacteria by Acromyrmex
leaf-cutting ants", The ISME Journal, 1 (4): 313–320, doi:10.1038/ismej.2007.41 . ^ Ballari, S. A. & Farji-Brener, A. G. (2006), "Refuse dumps of the leaf-cutting ants as a deterrent for ant herbivory: does refuse age matter?", The Netherlands Entomological Society, 121 (3): 215–219, doi:10.1111/j.1570-8703.2006.00475.x .

External links[edit]

Media related to Acromyrmex
at Wikimedia Commons

Taxon identifiers

Wd: Q1044887 BugGuide: 38824 EoL: 32565 EPPO: 1ACRXG GBIF: 1320640 ITIS: