Acromyrmex octospinosus
Encyclopedia
Acromyrmex octospinosus is a species
of New World ants of the subfamily Myrmicinae
of the genus
Acromyrmex. It is found in the wild naturally in Central America
ranging from southern Mexico
down to Panama
; and across northern South America
in Venezuela
.
within the tribe Attini.
Acromyrmex can be identified from the closely related Atta genus
of leafcutter ants since they have 4 pairs of spines and a rough exoskeleton on the upper surface of the thorax
.
A mature Acromyrmex octospinosus colony has a relatively small colony size of approximately 50,000 ants, mostly sterile female workers. They are divided into castes
, based mostly on size, that perform different functions. Acromyrmex 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 genera of leafcutter ants Atta, meaning that there is comparatively less differential in size 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.
It takes around 18 months for the colony to reach maturity but the queen of Acromyrmex octospinosus colony lives for 10 to 12 years and lays around 600 eggs per day at her peak.
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 media workers 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 and it is with this that 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 foodplant 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 and the amount of foliage they strip means they have become agricultural pests on the various Caribbean islands they have been introduced on, such as Guadeloupe
.
Foundresses of the leaf-cutting ant Acromyrmex octospinosus forage for leaves as garden substrate (semi-claustral foundation). The fungal pellet and substrate usually are attached to rootlets, which are used as a platform for the garden. This arrangement keeps the garden suspended away from the earthen chamber of the underground nest during early colony growth, and it serves to minimize contact between the garden and contaminants. A. octospinosus foundresses produce from 3 to 7 workers in 2.7 months after founding the nest, but workers do not forage for substrate at this time. Incipient nests died or were abandoned at a monthly rate of about 50%. The ants routinely clean their legs before manipulating the garden substrate. The foundresses use their fore-legs to rub the surface of the metapleural gland, and they then use typical grooming behaviors to pass the forelegs through the mouthparts, after which the ant then licks the garden substrate. Similarly, ants apparently use their mouths to transfer fecal droplets to their legs. These grooming behaviors are prophylactic behaviors that may help the foundress maintain a hygienic garden.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of New World ants of the subfamily Myrmicinae
Myrmicinae
Myrmicinae is a subfamily of ants. There are about 140 genera within the group, with the family being cosmopolitan. The pupae lack cocoons. Some species retain a functional sting. The petioles of Myrmicinae consist of two nodes...
of the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Acromyrmex. It is found in the wild naturally in Central America
Central America
Central America is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. When considered part of the unified continental model, it is considered a subcontinent...
ranging from southern Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
down to Panama
Panama
Panama , officially the Republic of Panama , is the southernmost country of Central America. Situated on the isthmus connecting North and South America, it is bordered by Costa Rica to the northwest, Colombia to the southeast, the Caribbean Sea to the north and the Pacific Ocean to the south. The...
; and across northern South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
in Venezuela
Venezuela
Venezuela , officially called the Bolivarian Republic of Venezuela , is a tropical country on the northern coast of South America. It borders Colombia to the west, Guyana to the east, and Brazil to the south...
.
Overview
Commonly known as "leaf-cutter ants" they are a species of ant from one of the two genera of advanced attinesFungus-growing ants
The fungus-growing ants comprises all the known fungus-growing ant species in the world participating in ant-fungus mutualism. Leafcutter ants, including Atta and Acromyrmex, make up 2 of the genera.-See also:...
within the tribe Attini.
Acromyrmex can be identified from the closely related Atta genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of leafcutter ants since they have 4 pairs of spines and a rough exoskeleton on the upper surface of the thorax
Thorax
The thorax is a division of an animal's body that lies between the head and the abdomen.-In tetrapods:...
.
A mature Acromyrmex octospinosus colony has a relatively small colony size of approximately 50,000 ants, mostly sterile female workers. They are divided into castes
Eusociality
Eusociality is a term used for the highest level of social organization in a hierarchical classification....
, based mostly on size, that perform different functions. Acromyrmex exhibit a high degree of biological polymorphism
Polymorphism (biology)
Polymorphism in biology occurs when two or more clearly different phenotypes exist in the same population of a species — in other words, the occurrence of more than one form or morph...
, 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 genera of leafcutter ants Atta, meaning that there is comparatively less differential in size 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.
It takes around 18 months for the colony to reach maturity but the queen of Acromyrmex octospinosus colony lives for 10 to 12 years and lays around 600 eggs per day at her peak.
Like Atta, Acromyrmex subsists mostly on a particular species of fungus (genus Leucocoprinus
Leucocoprinus
Leucocoprinus is a genus of fungi in the family Agaricaceae. Its best known member is the yellow pot-plant mushroom , found worldwide. The type species is Leucocoprinus cepistipes...
) which it cultivates on a medium of masticated leaf tissue. This is the sole food of the queen
Eusociality
Eusociality is a term used for the highest level of social organization in a hierarchical classification....
and other colony members that remain in the nest. The media workers 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 and it is with this that 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 foodplant 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 and the amount of foliage they strip means they have become agricultural pests on the various Caribbean islands they have been introduced on, such as Guadeloupe
Guadeloupe
Guadeloupe is an archipelago located in the Leeward Islands, in the Lesser Antilles, with a land area of 1,628 square kilometres and a population of 400,000. It is the first overseas region of France, consisting of a single overseas department. As with the other overseas departments, Guadeloupe...
.
Foundresses of the leaf-cutting ant Acromyrmex octospinosus forage for leaves as garden substrate (semi-claustral foundation). The fungal pellet and substrate usually are attached to rootlets, which are used as a platform for the garden. This arrangement keeps the garden suspended away from the earthen chamber of the underground nest during early colony growth, and it serves to minimize contact between the garden and contaminants. A. octospinosus foundresses produce from 3 to 7 workers in 2.7 months after founding the nest, but workers do not forage for substrate at this time. Incipient nests died or were abandoned at a monthly rate of about 50%. The ants routinely clean their legs before manipulating the garden substrate. The foundresses use their fore-legs to rub the surface of the metapleural gland, and they then use typical grooming behaviors to pass the forelegs through the mouthparts, after which the ant then licks the garden substrate. Similarly, ants apparently use their mouths to transfer fecal droplets to their legs. These grooming behaviors are prophylactic behaviors that may help the foundress maintain a hygienic garden.
Sub-species
The species Acromyrmex octospinosus contains the following subspecies- Acromyrmex octospinosus cubanus WheelerWilliam Morton WheelerWilliam Morton Wheeler, Ph.D. was an American entomologist, myrmecologist and Harvard professor.-Early life:...
, 1937 - Acromyrmex octospinosus echinatior Forel, 1899
- Acromyrmex octospinosus ekchuah WheelerWilliam Morton WheelerWilliam Morton Wheeler, Ph.D. was an American entomologist, myrmecologist and Harvard professor.-Early life:...
, 1937 - Acromyrmex octospinosus inti WheelerWilliam Morton WheelerWilliam Morton Wheeler, Ph.D. was an American entomologist, myrmecologist and Harvard professor.-Early life:...
, 1937 - Acromyrmex octospinosus octospinosus Reich, 1793
- Acromyrmex octospinosus volcanus WheelerWilliam Morton WheelerWilliam Morton Wheeler, Ph.D. was an American entomologist, myrmecologist and Harvard professor.-Early life:...
, 1937
Synonyms
- Acromyrmex guentheri EmeryCarlo EmeryCarlo Emery was an Italian entomologist.Born in Naples, Carlo Emery was professor of Zoology at the University of Bologna. He later worked in Geneva...
, 1894 - Acromyrmex pallida WheelerWilliam Morton WheelerWilliam Morton Wheeler, Ph.D. was an American entomologist, myrmecologist and Harvard professor.-Early life:...
, 1937 - Formica octospinosa Reich, 1793