Bigheaded Ant (BHA), pheidole megacephala (fabricius).
The Big Headed ant has been named one of the world’s worst invasive species. It is wreaking havoc on native ants in South Florida and becoming a increasing nuisance across the region. Knowing more about this species can help you protect yourself from its potentially destructive habits.
What is the bigheaded ant?
The Bigheaded ant (Pheidole megacephala) is an invasive tramp ant that has been nominated as one of the “world’s worst” invaders due to its potential to displace other native ants and become a pervasive nuisance. This species receives its name from the large-sized head of the major worker “soldier” and has been a pest in South Florida for many years. Of the 17 Pheidole species present in Florida, 14 are native to the region.
Does the Big Headed Ant Cause Damage?
No, the Big Headed Ant usually will not sting or bite unless the nest is disturbed and it does not cause damage to homes or properties.
What are the identifying characteristics of the bigheaded ant?
The bigheaded ant (Pheidole megacephala) is an invasive species found throughout South Florida in approximately 17 counties. It is a soil-nesting ant that can create foraging tubes, and it is often mistaken for subterranean termites. The bigheaded ant has identifying characteristics such as piles of loose sandy soil (“dirt piles”), the presence of foraging trails inside the home (in bathrooms, kitchens, around doors, and windows), foraging activity on exterior paved or brick walkways and driveways, numerous colonies that usually extend across property lines, and soil displaced from excavating underneath walkways or driveways.
Where did the big headed ant come from?
The big headed ant (Pheidole megacephala) originally comes from the Indian Ocean island of Mauritius, but is now found in many subtropical and tropical regions all over the world. It has also been reported in Florida, with original reports mentioning the Everglades, Key West and St. Augustine, as well as Miami Dade and Broward Counties.
What are the chararaceristics of the Big Headed Ant?
-Major and minor workers with dimorphic sizes, major workers measuring 3 to 4 mm and minor workers measuring 2 mm
-Front half of the major worker’s head is sculptured, back half is smooth and shiny
-Two-segmented petiole (waist)
-Post-petiolar node is conspicuously swollen
-Twelve-segmented antennae with a three-segmented club
-Whole body is covered with sparse, long hairs
-Pair of short propodeal spines (spines on waist)
-Generally a dark spot on the underside of the gaster
Other ants that are confused with Big Headed Ants.
Sometimes confused with RIFA red imported fire ants, RIFA workers are polymorphic BHA workers are dimorphic,
it is slightly smaller, darker colored, and less shiny than rifa.
Both nest in the soil.
1. Field Ants (Formica spp.)
2. Cornfield Ants (Lasius spp.)
3. Pharaoh Ants (Monomorium pharaonis)
4. Southern Fire Ants (Solenopsis xyloni)
5 Texas Leafcutting Ants (Atta texana)
Breeding and Mating Habits of The Big Headed Ant
The Big Headed Ant has a complete metamorphosis life cycle, with colonies containing large numbers of fertile queens. These colonies are capable of producing year-round broods in tropical and sub-tropical regions, and can form almost continuous supercolonies that exclude most other ant species.
In Australia, the dispersal of new colonies occurs through a process known as “budding”, where no nuptial flights are observed. However, in south Florida nuptial flights of alates (winged individuals) can be observed during the winter and spring months. Following these nuptial flights, fertilized queens will drop their wings and find a suitable nesting site where they will begin laying eggs.
Foraging and feeding of the big headed ant
The big headed ant is an omnivore and can feed on sweet honeydew, liquids, dead insects, and soil invertebrates. Foragers of this species will quickly recruit nest mates to a food source once it is found. These ants typically create foraging tunnels with numerous entrances which can be seen along the surface of the soil. Once prey is discovered, workers will bring it back to the nest and dissect it for consumption. In addition, these ants will also leave trails of foragers along tree trunks that climb up into the canopies of tall trees as well as on exterior walls of structures such as attics. Trophallaxis between minor and major workers or between two minor workers can also be observed when they exchange food.
Nest sites of The Big Headed Ant
1. Soils, lawns and flowerbeds
2. Under cement slabs and flower pots
3. Around trees and water pipes
4. Along the base of structures and walkways
5. Edges where lawns meet sidewalks
6. Piles of soil that have been deposited
7. Edges along lawns, walkways, or roadways
Control of Big Headed Ants
To effectively control Big Headed Ants (BHA), we recommend a combination of residual sprays and granular baits. We suggest using residual spray products that contain either fipronil, bifenthrin or permethrin. Two residual products that have been found to be effective in providing some degree of control for around two weeks are Transport (bifenthrin, acetamiprid) and Arena clothianidin). As permethrin has been found to be ineffective against BHA, it is best avoided.
For longer-term control, granular baits should also be used. Two such baits that can provide control up to 4 weeks are Siesta (metaflumizone) and MaxForce (fipronil). For an even better outcome, baits containing an insect growth regulator should be used; such as Extinguish Plus (hydramethylnon, S-methoprene). Research has shown that a methoprene bait was effective in reducing a BHA population.
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