Q and A: With the evening rains have come the thousands of ants. What can I do to rid these pests from my home?
from N.H., in Fort Myers
There are several species of ants found in or around houses in Florida. In general, the most common ants can be grouped as house infesting, yard infesting, and carpenter ants. The most commonly encountered are the pharaoh, ghost, carpenter, native fire, imported fire, crazy, bigheaded, and acrobat ants. It is important to understand the anatomy of ants. Ants have a narrow waist (pedicel or petiole) with one or two joints (nodes) between the thorax (upper body between neck and diaphragm) and abdomen (lower or back portion).
The pharaoh ant, Monomorium pharaonis, is rust colored and two millimeters long. It has two nodes on the petiole but no spines on the thorax. The antennae have twelve segments with a three-segmented club at the end.
The ghost ant, Tapinoma melanocephalum, is only one millimeter long with a black head and thorax. The abdomen and legs are clear. The petiole has one node and is hidden by the abdomen. This ant usually has a musty odor when squashed.
The carpenter ant, Camponotus abdonimalis, is a large ant between five and ten millimeters long. This ant has a red thorax and black abdomen. It has one node on the petiole. The thorax is evenly rounded when viewed from the side. The tip of the abdomen has a circle of hairs. Carpenter ants nest in hollow voids and pile wood chips nearby.
The native fire ant, Solenopsis geminata, is reddish brown to black and measures three to six millimeters in length. There are two nodes on the petiole and the antennae have ten segments with a two-segmented club. There are no spines on the thorax and the mandibles have no teeth. Workers can sting, but no white postule will form on the skin.
The imported fire ant, Solenopsis invicta, is reddish brown and measures three to six millimeters in length. These ants are exactly like the native fire ant except for the color and fact that the mandibles have four teeth. Fire ants build large mounds and their sting causes a white postule to form on the skin.
The crazy ant, Paratrchina longicornis, is black, three millimeters in length, and has long legs. It has one node on the petiole and antennae with twelve segments but no club. There is a circle of hairs at the tip of the abdomen. Worker ants are more easily identified because they move erratically.
The bigheaded ant, Pheidole megacephala, is a yellowish brown ant measuring two to three millimeters in length. There are two nodes on the petiole and the antennae have twelve segments with a three-segmented club. There are two spines that project from the thorax towards the abdomen. The workers will have unusually large heads.
The acrobat ant, Crematogaster spp., is usually light brown to a shiny black and grows to three millimeters in length. There are two nodes on the petiole and the antennae have twelve segments with a two-segmented club. There are two spines on the thorax and the abdomen is heart shaped. Acrobat ants hold their abdomens over their heads when disturbed.
With the ants identified, control can begin. Prevention is the best method and home cleanliness is key. Keep food containers tight, remove plants that may attract ants, and reduce moisture sources. Inspection is the next step. Location of the nest is important for control because ants are social insects. Determine the kind of ant and where it nests in order to find the colony. Keep a record of where ants are seen. They usually travel the same path. If possible follow these trails back to the nest. Keep in mind that the nest may be some distance away from where ants are actually seen.
Chemical control of ants can be applied as a barrier, drench, nest and/or bait treatment. There are several chemicals labeled for homeowner use. Carbaryl (Sevin) can be applied as a spray, dust or granule but must be used outdoors. Chlorpyrifos (Dursban) which is being eliminated by law can be used in spray form indoors. Diazinon can be applied as a spray, dust or granule for indoor or outdoors use but follow the directions carefully because granules should not be used indoors and dusts should not be used outdoors. Fenoxycarb (Logic) is bait for indoor or outdoor use. Hydramethylnon (Combat) is bait for indoor use. Malathion spray or dust can be used outdoors. Propoxur is a chemical labeled for indoor or outdoor use. Finally, sulfuramid (Raid Max) is bait that can be used indoors. In many cases dust is the appropriate choice since ants can carry the poison back to the nest. Follow the label because it is the law, and using more than specified may not be safe for members of your household or the environment.