''Pheidole megacephala'' is a species of

ant Ants are eusocial insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from vespoid wasp ancestors in the Cretaceous period. More than 13,800 of an estimated total of 22 ...

in the family Formicidae. It is commonly known as the big-headed ant in the USA and the coastal brown ant in

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

. It is a very successful invasive species and is considered a danger to native ants in Australia and other places. It is regarded as one of the world's worst invasive ant species.''Pheidole megacephala''
Global Invasive Species Database, 3 Aug 2011 (archived)

Distribution

''Pheidole megacephala'' was described from a specimen from the island of

Mauritius Mauritius ( ; french: Maurice, link=no ; mfe, label=Mauritian Creole, Moris ), officially the Republic of Mauritius, is an island nation in the Indian Ocean about off the southeast coast of the African continent, east of Madagascar. It incl ...

by the

entomologist Entomology () is the scientific study of insects, a branch of zoology. In the past the term "insect" was less specific, and historically the definition of entomology would also include the study of animals in other arthropod groups, such as arach ...

Johan Christian Fabricius Johan Christian Fabricius (7 January 1745 – 3 March 1808) was a Danish zoologist, specialising in "Insecta", which at that time included all arthropods: insects, arachnids, crustaceans and others. He was a student of Carl Linnaeus, and is cons ...

in 1793, although a 1775 record exists for Egypt, under the name ''Formica edax''. Regardless of its origin, big-headed ants have since spread to many tropical and subtropical parts of the world.Featured Creatures
/ref>

Description

There are two types of worker ants, the major or soldier ant and the minor worker. The common name of bigheaded ant derives from the soldier's disproportionately large head. This has large

mandibles In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower tooth, teeth in place. The mandible sits beneath the maxilla. It is the only movabl ...

which may be used to crush seeds. The soldiers are about four millimetres in length, twice as long as the minor workers. The colour of both types varies from yellowish-brown or reddish-brown to nearly black. The rear half of the head is smooth and glossy and the front half sculptured. The twelve-segmented antennae are curved and have club-like tips. The waist or petiole is two-segmented with the node immediately behind conspicuously swollen. There are a pair of short, upward-facing spines on the waist. The body has sparse, long hairs.

Colonies and reproduction

Bigheaded ants nest in

colonies In modern parlance, a colony is a territory subject to a form of foreign rule. Though dominated by the foreign colonizers, colonies remain separate from the administration of the original country of the colonizers, the '' metropolitan state'' ...

underground. Colonies can have several queens and supercolonies can be formed by

budding Budding or blastogenesis is a type of asexual reproduction in which a new organism develops from an outgrowth or bud due to cell division at one particular site. For example, the small bulb-like projection coming out from the yeast cell is know ...

, when a queen and workers leave the original nest and set up a new colony nearby without swarming. In Florida,

nuptial flight Nuptial flight is an important phase in the reproduction of most ant, termite, and some bee species. It is also observed in some fly species, such as ''Rhamphomyia longicauda''. During the flight, virgin queens mate with males and then land to ...

s of winged ants take place during the winter and spring and afterwards, fertilized queens shed their wings and find a suitable site to found a new colony where they start laying

eggs Humans and human ancestors have scavenged and eaten animal eggs for millions of years. Humans in Southeast Asia had domesticated chickens and harvested their eggs for food by 1,500 BCE. The most widely consumed eggs are those of fowl, especial ...

. Each queen lays up to 290 eggs per month. The eggs hatch after two to four weeks and the legless white

larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. The ...

e, which are fed by the workers,

pupa A pupa ( la, pupa, "doll"; plural: ''pupae'') is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in their ...

te about a month later. The adult workers emerge ten to twenty days after that.Hoffman B. 2006. Pheidole megacephala (insect). CSIRO Sustainable Ecosystems The minor workers are much more numerous than the soldiers. Trails of ants lead up trunks, along branches and into the canopies of trees and debris-covered foraging tunnels with numerous entrances are created on the surface of the ground. These may be confused with similar tubes built by subterranean

termite Termites are small insects that live in colonies and have distinct castes (eusocial) and feed on wood or other dead plant matter. Termites comprise the infraorder Isoptera, or alternatively the epifamily Termitoidae, within the order Blattode ...

s. ''P. megacephala'' can also live indoors.

Nutrition

The bigheaded ants feed on dead insects, small

invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...

s and honeydew excreted by insects such as

aphid Aphids are small sap-sucking insects and members of the superfamily Aphidoidea. Common names include greenfly and blackfly, although individuals within a species can vary widely in color. The group includes the fluffy white woolly aphids. A t ...

s, soft

scale insect Scale insects are small insects of the order Hemiptera, suborder Sternorrhyncha. Of dramatically variable appearance and extreme sexual dimorphism, they comprise the infraorder Coccomorpha which is considered a more convenient grouping than the ...

mealybug Mealybugs are insects in the family (biology), family Pseudococcidae, unarmored scale insects found in moist, warm habitats. Many species are considered pest (animal), pests as they feed on plant juices of greenhouse plants, house plants and sub ...

whiteflies Whiteflies are Hemipterans that typically feed on the undersides of plant leaves. They comprise the family Aleyrodidae, the only family in the superfamily Aleyrodoidea. More than 1550 species have been described. Description and taxonomy The ...

and

planthopper A planthopper is any insect in the infraorder Fulgoromorpha, in the suborder Auchenorrhyncha, a group exceeding 12,500 described species worldwide. The name comes from their remarkable resemblance to leaves and other plants of their environment ...

s. These sap-sucking bugs thrive in the presence of bigheaded ants, being more abundant on plants patrolled by ants than on those not so patrolled. Also, bigheaded ants are predators of the eggs of various species of moths such as the African sugarcane borer, common in sub-Saharan Africa. Green scale, ''Coccus viridis'', flourished when bigheaded ants protected their food source by removing

predators Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill the ...

such as

lady beetle Coccinellidae () is a widespread family of small beetles ranging in size from . They are commonly known as ladybugs in North America and ladybirds in Great Britain. Some entomologists prefer the names ladybird beetles or lady beetles as they ...

larvae and

lepidoptera Lepidoptera ( ) is an order (biology), order of insects that includes butterfly, butterflies and moths (both are called lepidopterans). About 180,000 species of the Lepidoptera are described, in 126 Family (biology), families and 46 Taxonomic r ...

n larvae.Direct and indirect interactions between ants (Pheidole megacephala), scales (Coccus viridis) and plants (Pluchea indica)
/ref> Foraging ants will alert others to new food sources. Honeydew is ingested but other foodstuffs are carried back to the nest by both major and minor workers who may transfer items of food between themselves. Anything too big to be moved may be dissected before being brought back to the nest.

Harmfulness

Bigheaded ants are a threat to biodiversity through the displacement of native invertebrate fauna and is a pest of agriculture through harvesting seeds and harbouring insects on crops. They are also known to chew on irrigation and telephone cabling as well as electrical wires.

References

External links

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{{Taxonbar, from=Q2703952

megacephala ''Megacephala'' is a small genus of beetles in the family Cicindelidae restricted to Africa; it was formerly a much larger genus, but its constituent species (including all of the New World species) have been subsequently placed in other genera, ...

Insects described in 1793 Hymenoptera of New Zealand Ants of New Zealand