User:Aroid Mania/Acromyrmex octospinosus

Acromyrmex octospinosus is a species of New World leaf cutting ants in the genus Acromyrmex of the subfamily Myrmicinae. It is distributed widely across southern Central America, including Costa Rica and Trinidad, as well as northern South America, from Venezuela to French Guiana. Worker ants of this species harvest live foliage from plants and bring them back to underground chambers within their nests where the leaves are used to cultivate a fungus which the colony depends on as a food source. Acromyrmex octospinosus is considered a significant agricultural pest across its range.

Taxonomy
The genus Acromyrmex contains 33 species and is a sister genus to Atta, which together constitute the most derived monophyletic group in the tribe Attini within Formicidae. The main synapomorphy of this tribe is that all members participate in fungus farming and fungus-ant mutualism.

Sub species
Acromyrmex octospinosus has six subspecies:
 * Acromyrmex octospinosus cubanus
 * Acromyrmex octospinosus echinatior
 * Acromyrmex octospinosus ekchuah
 * Acromyrmex octospinosus inti
 * Acromyrmex octospinosus octospinosus
 * Acromyrmex octospinosus volcanus

Description
Adult worker ants of this species are typically 8 to 9 mm in length, light brown in color, and have sharp triangular mandibles which intercross to excise foliage of plants. Workers of this species are known to form very large nest sizes and are polymorphic, sometimes ranging greatly in size between geographically distant colonies. This species can be easily distinguished from closely related Atta species on the basis of promesonotum spine count, where Acromyrmex octospinosus has three spines and Atta spp. have two.

Life history
Acromyrmex octospinosus has been documented living in a wide range of habitats including forests, woodlands, agricultural fields and residential areas. Nests are shallow and formed underground, in tree crevices/buttresses, and under rocks or man-made structures. This species has developed a mutualistic relationship with a fungus (Leucoagaricus gongylophorus) which is cultivated by the ants and used as a food source. Adults harvest live foliage from a wide range of plants using their razor-sharp mandibles and bring the leaf matter to underground chambers where it is converted into fungal substrate and suspended onto rootlets from above ground vegetation. The fungus then breaks down and survives off of the leaf substrate, which routinely has to be replaced by the ants.

Foundresses of the colony display distinct hygienic behavior involving cleaning their forelegs and removing fecal secretions before tending to the fungal garden to avoid contamination. Raw leaf matter is converted to fungal substrate in three steps; first the leaf surface is rasped by the mandibles, then it's macerated into a ball, and finally the mass is inoculated with fecal secretions and placed into the garden. Contamination from unwanted pathogens into the garden are a considerable threat to the colony's food supply and a number of actions are taken to counter microbe growth. An acidic pH is maintained in the fungal garden and a number of antibiotic compounds are produced, both from the metapleural gland and from bacterial symbionts (Streptomyces spp.) which are then applied to the fungal garden to minimize outbreaks of fungal and bacterial pathogens.

Distribution and management
Acromyrmex octospinosus is widely distributed throughout the northern South America, southern Central America and the Caribbean Islands. The species is very adaptable in variety of habitats, which has allowed it to colonize natural, residential and agricultural areas throughout its range. Adults of this species collect immense amounts of plant material to sustain colonies which has considerably impacted forests and agricultural crops, making this species one of the most important agricultural pests in the regions it inhabits. Historically synthetic insecticides have been applied in large quantities to control Acromyrmex species in crop fields. Recently, however, more environmentally-safe management techniques have since been implemented including the field application of certain plant extracts (Mammea americana and Nerium oleander) which have been proven effective as repellants and toxic if ingested by the ants.