African Ant Found in a Connecticut Structure

On October 16, 2015 a pest control operator brought some very small ants to the information office of the Valley Laboratory, CAES in Windsor, Conn. The samples were from a large structure in Cromwell, Conn., and were found throughout the structure. The ants had been a low level problem for some years, but had recently become a large problem. Any food crumb dropped was quickly covered by these ants. The pest control operator reported that no winged forms had been found in the building. Initial research showed this ant was not a common species. Jane O’Donnell, of the University Connecticut and Stefan Cover, of Harvard University, were consulted and a diagnosis of Pheidole megacephala was arrived at.

 

Native to the Afrotropics, this is an aggressive ant that is now distributed in many locations worldwide. According to AntWeb, it has been found in Southern California, Missouri, Florida and Baltimore, Maryland in the United States. This is the farthest north this ant has been reported to date.

 

DESCRIPTION: Commonly called the bigheaded ant (BHA), Pheidole megacephala has two worker castes: larger sized individuals called the major caste and smaller individuals called the minor caste. The head of this ant species is disproportionately larger than the body in the major caste and less so in the minor cast.

 

A few major and many minor workers were brought to the Connecticut Agricultural Experiment Station with the major workers 3 mm in length and the minor workers 2 mm in length. The head is a darker red brown than the body and the gaster is darker brown on both castes. There are long, upright, yellow hairs sparsely scattered over most of the body. The oval-shaped head, of the minor worker, and larger heart-shaped head of the major worker have antennae that are twelve segmented with a 3-segmented club. The antennal scape is longer than the head in the minors we received and shorter than the head in the major workers. The sculpturing on the face is different in the two castes. There are small wrinkles on the lower face on either side of where the antennae are inserted in the minor worker, but on the major workers there is more sculpturing across the entire lower face. Mandibles contain 5 – 7 teeth.

 

The thorax has a ‘broken back’ look and is pitted on the last two segments. When viewed in profile, the middle segment is lower than the first and the last segment drops down even further and has two short spines on either side.

The abdomen has two pedicels. The first is elongated with a stalk attaching to the thorax. This segment is also pitted. The post petiole is rounded when viewed from above and has a smooth surface with a few hairs.

 

BIOLOGY: Pheidole megacephala is an omnivorous ant, preying on other insects as well as feeding on any human or animal food of plant or animal origin. In Hawaii, BHA tends mealybugs on papaya to harvest their honeydew. They do not sting unless the nest is disturbed and the sting is not painful.

 

This ant usually nests in the soil. In Florida it constructs foraging tubes of plant debris to move around above ground. Where large nests are found near buildings, workers frequently forage in buildings for food. Trails of workers can be seen moving long distances between food sources and the nest.

 

In buildings BHA can nest in wall voids, suspended ceilings and other spaces. They do no structural damage. It remains to be seen if they can nest in large potted plants.

 

Outdoor colonies can get very large and displace native ant species with their aggressive behavior. It is not known if they can overwinter outdoors in New England.

 

This ant may be moving around the globe in soils associated with potted houseplants or agricultural products (Stefan Cover, personal communication). The structure in which they were found in Connecticut has many large palm and other houseplants. Many houseplants are produced in the tropics where this ant is present in large numbers.

 

MANAGEMENT: In buildings, removing food sources should help reduce ant populations. Since BHA will eat spilled food crumbs, keeping kitchens and eating areas clean and vacuumed is necessary. Be sure food waste garbage cans are sealed tightly. Keeping the building as free as possible of other insects will reduce food available to these ants. Also controlling living insects on house plants such as aphids, mealybugs or scales, which secrete honeydew, is needed as well.

 

Trials in pineapple fields in Hawaii showed Amdro in bait stations managed BHA populations well (Taniguchi, Thompson and Sipes, 2006).

 

Field trials in Florida concluded that 28 days post treatment, MaxForce Fire Ant Bait with fipronil, provided the best suppression of BHA (Warner, Yang and Scheffrahn, 2008).

 

In Connecticut BHA has only been reported to date as being in a building. If true, this limits the reinfestation of ants from outside the treatment area. Both Amdro and MaxForce are labelled for use in buildings in Connecticut. More research is needed to find the pathway by which BHA arrived here and to see if we can get eradication using newer, possibly more effective, products.

 

Voucher specimens of Pheidole megacephala were deposited in the following collections: The Connecticut Agricultural Experiment Station, New Haven; The University of Connecticut, Entomology Collection; and the California Academy of Sciences, San Francisco.

 

REFERENCES :

AntWiki: http://www.antwiki.org/wiki/Pheidole_megacephala. Accessed 23 October, 2015.

Taniguchi, G., T. Thompson and B. Sipes. 2006. Prevention and control of the big-headed ant, Pheidole megacephala, (Hymenoptera: Formicidae) in pineapple cultivation using bait stations with Amdro. Acta Hort. (ISHS) 702:173-177.

Warner, J., and Rudolf H. Scheffrahn. Revised 2013. Bigheaded ant, Pheidole megacephala (Fabricius). UF/IFAS Featured Creatures. EENY-369. Website: http://creatures.iflas.ufl.edu/urban/ants/bigheaded_ant.htm

Warner, J., R Yang and R. H. Scheffrahn. 2008. Efficacy of selected bait and residual toxicants for control of bigheaded ants, Pheidole megacephala, (Hymenoptera: Formidicae), in large field plots. Florida Entomologist v91 #2, 227-282.

 

The author thanks Katherine Dugas and Nathaniel Child for their technical assistance.