The ants commonly referred to as “big-headed ants” belong to the Pheidole genus, which is made up of more than 1,000 documented species worldwide, several of which are well known pests of homes in the southern US. According to a recent nationwide survey of pest control professionals, big-headed ants were the seventh most frequently managed ant pests within and around US homes during 2016. Big-headed ant colonies are usually established in ground soil beneath objects like rocks, wood piles, and landscaping ornaments, but colonies are also commonly initiated within decayed wood, such as stumps, fallen branches, and sometimes, rotten structural lumber. Big-headed ant colonies contain two types of workers known as “major workers” and “minor workers,” and while both are comparable in body size, only major workers possess the noticeably large heads that earned this species its common name.
Major and minor workers are both reddish-brown in color and between 2.4 and 3.8 inches in length. Although major and minor workers both belong to the worker caste, major workers are commonly referred to as “soldiers” due to their habit of defending minor workers during foraging expeditions. Major workers use their disproportionately large head as a weapon against enemy ants and other hostile arthropods, and minor workers are often mistaken for red-imported fire ants due to their similar appearance and nesting behaviors. Unlike red-imported fire ants, big-head ant workers possess 12-segmented antennae with a 3-segmented club at the end.
Multiple big-headed ant species are known indoor pests in the US, including P. bicarinata, P. hyatti and P. megacephala, but P. dentata infests homes in the country most frequently, and they are particularly abundant in Houston and other urban and suburban areas along the Gulf Coast. Workers often invade homes in large numbers where they readily feed on a variety of food sources, such as meats, grease, liver, molasses, peanut butter, fruit juices and sweets. It is not uncommon for homeowners to find these ants infesting their kitchen cabinets and/or pantry. Big-headed ants rarely establish indoor nests, but they frequently establish multiple nests on properties in order to make repeated trips into homes to collect food sources. An insecticide application around the entirety of a home’s exterior foundation wall will prevent big-headed ants from foraging indoors, and baits are effective for eliminating colonies located within inaccessible areas. In order to eliminate nests found within indoor wall voids, minimal amounts of insecticide dust, granular baits, or liquid baits can be injected through tiny and inconspicuous holes drilled into walls.
Have you ever encountered ants with unusually large heads within your home?