{"id":13739,"date":"2021-03-01T14:38:45","date_gmt":"2021-03-01T04:38:45","guid":{"rendered":"https:\/\/professionalpestmanager.com\/?p=13739"},"modified":"2022-11-05T11:04:49","modified_gmt":"2022-11-05T01:04:49","slug":"in-focus-big-headed-ant","status":"publish","type":"post","link":"https:\/\/professionalpestmanager.com\/nz\/pest-control-ants\/in-focus-big-headed-ant\/","title":{"rendered":"IN FOCUS: BIG-HEADED ANT"},"content":{"rendered":"

We take an in-depth look at big-headed ants, looking at their biology, behaviour and control options.<\/em><\/p>\n

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Big-headed ants are considered one of the 100 worst pests in the world. Not only do they create issues in agricultural areas and inside buildings, where they can cause faults with electrical services, as an invasive pest they readily out-compete and displace native wildlife, particularly invertebrates and especially ants. As a result they are seen as a major threat to ecosystems and biodiversity.<\/p>\n

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First recorded on the island of Mauritius in the Indian Ocean, the big-headed ant is thought to have originated in the tropical areas of Africa; indeed the \u2018megacephala\u2019 group seems quite diverse on the African island of Madagascar. Human-assisted transport has ensured the ant has spread to many sub-tropical and tropical regions throughout the world. Having arrived in Australia around 100 years ago, it is now found in many areas of the mainland.<\/p>\n

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Species snapshot<\/strong><\/h2>\n

Latin name:<\/strong> Pheidole<\/em> megacephala<\/em>.<\/p>\n

Common name(s):<\/strong> Big-headed ant, African big-headed ant, coastal brown ant.<\/p>\n

Description:<\/strong> Brown ant, often with a darker gaster. They are readily identified by the dimorphic workers \u2013 the smaller workers are small (c. 2 mm long) and the larger workers (3-4 mm) have the oversized head, after which the species is named.<\/p>\n

Native distribution:<\/strong> Tropical areas of Africa.Current distribution: Many tropical and sub-tropical\u00a0areas globally.<\/p>\n

Nest location:<\/strong> Typically a soil-nesting species, thriving in moist disturbed areas, particularly under logs, rocks and pavers. Will readily nest inside in ceilings, wall cavities and power outlets.<\/p>\n

Nest structure:<\/strong> Multiple queens and multiple nests as part of the same colony. Budding can create \u2018super colonies\u2019.<\/p>\n

Diet:<\/strong> Highly varied diet (protein, oils and sugar) including dead and live invertebrates, plant material, honeydew, food scraps.<\/p>\n

Sting\/bite:<\/strong> Big-headed ants do not sting and have a very mild bite (to humans).<\/p>\n<\/div>\n

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Although big-headed ants are assumed to be Pheidole megacephala,<\/em> it appears there are a number of species in the \u2018megacephala\u2019 group, including a number of unidentified species. They all have the unmistakable big-headed soldier. Their oversized heads contain the large muscles for dismembering prey, cracking seeds and colony defence.<\/p>\n

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Interestingly, it appears that the big- headed ants in Australia have the largest heads of any specimens collected globally.1<\/sup> Researchers believe that the heads of soldiers in Australia have increased in size over a relatively short period of time since their arrival, in response to the presence of the more aggressive, competing ant species in Australia. However, this increased selection pressure does not appear to have influenced the number of soldiers produced \u2013 soldiers appear to comprise 1% of all nests analysed globally.<\/p>\n

The colour of big-headed ants and size of the smaller worker sometimes cause them to be confused with the various Monomorium<\/em> species, and sometimes even with the red important fire ant. But the presence of larger workers is generally a big giveaway and it can be readily differentiated from red imported fire ants, which have a continuous range of worker sizes, a more aggressive nature (and nasty sting!) and a unique nest mound of friable soil.<\/p>\n

One of the main reasons why big-headed ants are so successful in invading new areas is because they have multiple queens per colony and produce brood year- round in their preferred tropical and sub-tropical areas. They expand their nest size through budding, which allows them to create \u2018super colonies\u2019 that can exclude other ant species from an area. It appears that in Australia, dispersal is exclusively through budding (no alates have been observed)2<\/sup>, although in Florida, nuptial flights are observed in winter and spring.<\/p>\n

Their nests become obvious through the displacement of dirt, with obvious piles seen in lawns, around structural elements and particularly in and around pavers. Interestingly, big-headed ants can also building shelter tubes from dirt and other materials, which can look like termite mud tubes at first glance. They can also build partial shelter tubes over their foraging trails on the surface of the soil. Their foraging trails can cover significant distances to substantial food sources.<\/p>\n

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Big-headed ants can build shelter tubes that superficially look like termite activity (photo credit: Andrew Critchley, Instinct Pest Management)<\/figcaption><\/figure>\n

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Their omnivorous diet is another key reason for their success. Their food sources include: scavenging dead invertebrates; tackling live prey (mainly invertebrates but some small vertebrates); harvesting honeydew from sap-sucking pests; attacking plants, fruits and their roots directly; and feeding on food scraps left by humans. Big-headed ants do not sting, they overwhelm any live prey with sheer numbers. To humans their bite is virtually painless.<\/p>\n

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