Pheidole megacephala
Encyclopedia
Pheidole megacephala is a species of ant
in the family Formicidae. It is commonly known as the bigheaded ant in the USA and the coastal brown ant in Australia. It is a very successful invasive species and is considered a danger to native ants in Australia and other places. It has been nominated as one of the hundred "World's Worst" invaders.
by the entomologist
, Johan Christian Fabricius
in 1793 but has since spread to many tropical and subtropical parts of the world.
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.
underground. Colonies can have several queens and super-colonies can be formed by budding, when a queen and workers leave the original nest and set up a new colony nearby without swarming. In Florida, nuptial flights 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
. Each queen lays up to 290 eggs per month. The eggs hatch after two to four weeks and the legless white larvae
, which are fed by the workers, pupate
about a month later. The adult workers emerge ten to twenty days after that.
The bigheaded ants feed on dead insects, small invertebrate
s and honeydew
excreted by insects such as aphid
s, soft scale insect
s, mealybug
s, whiteflies
and planthopper
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. Green scale
, Coccus viridis, flourished when bigheaded ants protected their food source by removing predators
such as lady beetle
larvae and lepidopteran
larvae. 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
s. 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.
Ant
Ants are social insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from wasp-like ancestors in the mid-Cretaceous period between 110 and 130 million years ago and diversified after the rise of flowering plants. More than...
in the family Formicidae. It is commonly known as the bigheaded ant in the USA and the coastal brown ant in Australia. It is a very successful invasive species and is considered a danger to native ants in Australia and other places. It has been nominated as one of the hundred "World's Worst" invaders.
Distribution
The bigheaded ant was originally recorded on the island of MauritiusMauritius
Mauritius , officially the Republic of Mauritius is an island nation off the southeast coast of the African continent in the southwest Indian Ocean, about east of Madagascar...
by the entomologist
Entomology
Entomology is the scientific study of insects, a branch of arthropodology...
, Johan Christian Fabricius
Johan Christian Fabricius
Johan Christian Fabricius was a Danish zoologist, specialising in "Insecta", which at that time included all arthropods: insects, arachnids, crustaceans and others...
in 1793 but has since spread to many tropical and subtropical parts of the world.
Description
There are two types of worker ant, 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 mandiblesMandible (insect)
Insect mandibles are a pair of appendages near the insect’s mouth, and the most anterior of the three pairs of oral appendages . Their function is typically to grasp, crush, or cut the insect’s food, or to defend against predators or rivals...
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
Petiole (insect)
In entomology, the term petiole is most commonly used to refer to the constricted first metasomal segment of members of the Hymenopteran suborder Apocrita; it may be used to refer to other insects with similar body shapes, where the metasomal base is constricted...
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.
Biology
Bigheaded ants nest in coloniesColony (biology)
In biology, a colony reference to several individual organisms of the same species living closely together, usually for mutual benefit, such as stronger defense or the ability to attack bigger prey. Some insects live only in colonies...
underground. Colonies can have several queens and super-colonies can be formed by budding, when a queen and workers leave the original nest and set up a new colony nearby without swarming. In Florida, nuptial flights 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
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
. Each queen lays up to 290 eggs per month. The eggs hatch after two to four weeks and the legless white larvae
Larva
A larva 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...
, which are fed by the workers, pupate
Pupa
A pupa is the life stage of some insects undergoing transformation. The pupal stage is found only in holometabolous insects, those that undergo a complete metamorphosis, going through four life stages; embryo, larva, pupa and imago...
about a month later. The adult workers emerge ten to twenty days after that.
The bigheaded ants feed on dead insects, small invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s and honeydew
Honeydew (secretion)
Honeydew is a sugar-rich sticky liquid, secreted by aphids and some scale insects as they feed on plant sap. When their mouthpart penetrates the phloem, the sugary, high-pressure liquid is forced out of the gut's terminal opening. Honeydew is particularly common as a secretion in the Hemipteran...
excreted by insects such as aphid
Aphid
Aphids, also known as plant lice and in Britain and the Commonwealth as greenflies, blackflies or whiteflies, are small sap sucking insects, and members of the superfamily Aphidoidea. Aphids are among the most destructive insect pests on cultivated plants in temperate regions...
s, soft scale insect
Scale insect
The scale insects are small insects of the order Hemiptera, generally classified as the superfamily Coccoidea. There are about 8,000 species of scale insects.-Ecology:...
s, mealybug
Mealybug
Mealybugs are insects in the family Pseudococcidae, unarmored scale insects found in moist, warm climates. They are considered pests as they feed on plant juices of greenhouse plants, house plants and subtropical trees and also acts as a vector for several plant diseases.-Distribution:Mealybugs...
s, whiteflies
Whitefly
The whiteflies, comprising only the family Aleyrodidae, are small hemipterans. More than 1550 species have been described. Whiteflies typically feed on the underside of plant leaves.-Agricultural threat:...
and planthopper
Planthopper
A planthopper is any insect in the infraorder Fulgoromorpha within the Hemiptera. The name comes from their remarkable resemblance to leaves and other plants of their environment and from the fact that they often "hop" for quick transportation in a similar way to that of grasshoppers. However,...
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. Green scale
Coccus viridis
Coccus viridis is a soft scale insect in the family Coccidae with a wide host range. It is commonly known as green scale or sometimes coffee green scale because it is a major pest of coffee crops throughout the world.-Description:...
, Coccus viridis, flourished when bigheaded ants protected their food source by removing predators
Predation
In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...
such as lady beetle
Coccinellidae
Coccinellidae is a family of beetles, known variously as ladybirds , or ladybugs . Scientists increasingly prefer the names ladybird beetles or lady beetles as these insects are not true bugs...
larvae and lepidopteran
Lepidoptera
Lepidoptera is a large order of insects that includes moths and butterflies . It is one of the most widespread and widely recognizable insect orders in the world, encompassing moths and the three superfamilies of butterflies, skipper butterflies, and moth-butterflies...
larvae. 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
Termite
Termites are a group of eusocial insects that, until recently, were classified at the taxonomic rank of order Isoptera , but are now accepted as the epifamily Termitoidae, of the cockroach order Blattodea...
s. 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.