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   Pheidole megacephala (insect)  français     
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      Pheidole megacephala worker (soldier) dorsal view (Photo: Japanese Ant Color Image Database) - Click for full size   Pheidole megacephala  (Photo: Mark Deyrup , AntWeb, hosted by California Academy of Sciences) - Click for full size   Pheidole megacephala  (Photo: Mark Deyrup , AntWeb, hosted by California Academy of Sciences) - Click for full size   Pheidole megacephala worker (soldier) lateral view (Photo: Japanese Ant Color Image Database) - Click for full size   Pheidole megacephala worker (soldier) frontal (head) view (Photo: Japanese Ant Color Image Database) - Click for full size   Pheidole megacephala (Photo: Camboué, AntWeb, hosted by California Academy of Sciences) - Click for full size
    Taxonomic name: Pheidole megacephala (Fabricius 1793)
    Synonyms: Atta testacea Smith 1858, Formica edax Forskal 1775, Formica megacephala Fabricius 1793, Myrmica laevigata F. Smith, Myrmica suspiciosa Smith 1859, Myrmica trinodis Losana 1834, Oecophthora perniciosa Gerstacker 1859, Oecophthora pusilla Heer 1852, Pheidole janus F. Smith, Pheidole laevigata Mayr
    Common names: big-headed ant (English), brown house-ant (English), coastal brown-ant (English), Grosskopfameise (German), lion ant (English)
    Organism type: insect
    Pheidole megacephala is one of the world's worst invasive ant species. Believed to be native to southern Africa, it is now found throughout the temperate and tropical zones of the world. It is a serious threat to biodiversity through the displacement of native invertebrate fauna and is a pest of agriculture as it harvests seeds and harbours phytophagous insects that reduce crop productivity. Pheidole megacephala are also known to chew on irrigation and telephone cabling as well as electrical wires.
    Description
    It is a small ant (minor workers approximately 2mm long and major workers 3-4mm long), ranging in colour from a pale yellow to a very dark brown. The first antennal segment (scape) of the minor workers far exceeds the top of the head, and is covered in many long hairs. There are no spines on the front of the body (pronotum), but two very small spines on the rear of the body (propodeum) facing almost directly up. There are many small punctations on the rear side of the body, and side of the head, but remaining body areas are smooth and shiny. The entire body is covered in many sparse, long hairs. The second waist segment (post petiole) is conspicuously swollen.

    Please click on AntWeb: Pheidole megacephala for more images and assistance with identification. The AntWeb image comparison tool lets you compare images of ants at the subfamily, genus, species or specimen level. You may also specify which types of images you would like to comare: head, profile, dorsal, or label.
    Please see PaDIL (Pests and Diseases Image Library) Species Content Page Ants: Coastal brown-ant for high quality diagnostic and overview images.

    Please follow this link for a fully illustrated Lucid key to common invasive ants [Hymenoptera: Formicidae] of the Pacific Island region [requires the most recent version of Java installed]. The factsheet on Pheidole megacephala contains an overview, diagnostic features, comparision charts, images, nomenclature and links. (Sarnat, 2008)

    Occurs in:
    agricultural areas, coastland, natural forests, planted forests, range/grasslands, riparian zones, ruderal/disturbed, scrub/shrublands, urban areas, wetlands
    General impacts
    This ant displaces most native invertebrate faunas directly through aggression, and as such is a serious threat to biodiversity. Evidence also exists of reductions in vertebrate populations where this ant is extremely abundant. Effects on plants and horticultural crops can be direct through the likes of seed harvesting, or indirect through the likes of harbouring phytophagous insects which reduce plant productivity. It is known to facilitate the invasion of introduced plant species. This ant is known to chew on irrigation, telephone cabling and electrical wires.
    Geographical range
    Native range: Believed to be native to southern Africa.
    Known introduced range: It is now widespread throughout the temperate and tropical zones of the world. It is favoured by shaded and moist environments, but can exist wherever there is anthropogenic disturbance.
    Introduction pathways to new locations
    Ignorant possession:
    Other: Sailing ships in the 18th and 19th centuries.
    Road vehicles (long distance): General frieght and household movements from infested areas.
    Seafreight (container/bulk):
    Translocation of machinery/equipment:


    Local dispersal methods
    Garden escape/garden waste:
    People sharing resources (local): Particularly garden or potted plants.
    Road vehicles:
    Translocation of machinery/equipment (local):
    Management information
    Preventative measures: Preventative management is the best option stopping the spread of this species, with attention focused on the movement of soils, particularly in potted plants, and the movement of all other materials from infested areas. The Pacific Ant Prevention Programme is a proposal prepared for the Pacific Plant Protection Organisation and Regional Technical Meeting For Plant Protection. This plan aims to prevent the red imported fire ant and other invasive ant species with economic, environmental and/or social impacts, entering and establishing in or spreading between (or within) countries of the Pacific Region.

    Physical: Fire may play an important role in controlling this ant in many areas by producing an environment less favourable to this ant, but providing a selective advantage to aggressive native ant species, or by direct destruction of colonies.

    Chemical: Good control is achieved using the bait 'Amdro' applied over the entire infested area. Complete eradication can be achieved within 24 hours. A major eradication event within Kakadu National Park, Australia, was completed by the end of 2002. Chemical control using general insecticides and chlorinated hydrocarbons such as DDT, heptachlor and Mirex® was the favoured option until relatively recently, with most of these chemicals now phased out due to environmental consequences. Latest options include the insect growth regulators (IGRs), methoprene, fenoxycarb and pyriproxyfen which regress ovarian tissues of fertile queens turning them sterile, and the stomach toxicant hydramethylnon, which kills all workers and reproductives that come into contact with it.

    Nutrition
    Omnivorous. Will capture and kill invertebrates and small vertebrates (e.g. bird hatchlings). Harvests seeds, and tends phytophagous insects. General scavenger.
    Reproduction
    Sexual reproduction by fertile queens. Insemination of virgin queens occurs once within the parent colony, then the male dies. Reproduction is year-round, but would vary according to climatic conditions of each locality.
    Queens have been documented to lay up to 292 eggs per month.
    Lifecycle stages
    This ant has a complete life-cycle, and developmental time and longevity of each stage is highly dependent on temperature. Incubation time of eggs ranges from13-32 days. Duration of the larval stage ranges from 23-29 days. Duration of the pupal stage ranges from 10-20+ days. Lifespans of minor workers have been shown to be 78 days at 21C, and 38 days at 27C.
    This species has been nominated as among 100 of the "World's Worst" invaders
    Reviewed by: Dr. Ben Hoffmann, CSIRO Sustainable Ecosystems, PMB 44 Winnellie, NT 0822, Australia
    Compiled by: IUCN SSC Invasive Species Specialist Group
    Updates with support from the Overseas Territories Environmental Programme (OTEP) project XOT603, a joint project with the Cayman Islands Government - Department of Environment
    Last Modified: Wednesday, 3 August 2011


ISSG Landcare Research NBII IUCN University of Auckland