Ants are among the most successful insects. Experts estimate that there could be 20,000 or more species of ants in the world. They have evolved to fill a variety of different ecological niches as predators, herbivores, leaf-cutters, seed-harvesters, aphid- tenders, and fungus-growers. They are found in deserts and rainforests, mountains and valleys, from the Arctic Circle to the tip of South America. They are interesting organisms that should be studied to better understand their unique behaviors and their roles in the earth's ecosystems.
They can also be pests, however. Fire ants and others may sting or bite people and animals. Pharaoh ants get into wounds and dressings in hospitals. House-infesting ants can become pests by their presence in kitchens and living areas. Carpenter ants tunnel into structural wood. Mound-building ants mar the appearance of lawns and landscaped areas. Sometimes ants must be managed to suppress a pest problem.
The Ant Colony and Life Cycle
Ants belong to the insect order Hymenoptera, which also includes the wasps and bees. Ants are distinguished from many of their nearest relatives by two characteristics: a narrow "waist" (the slender free-moving portion of the abdomen called a pedicel) and elbowed antennae.
Ants also differ from most other insects in that they are social, similar to termites and certain bees and wasps. This means that ants live in large cooperative groups called colonies. 2 or more generations overlap in the colony; adults take care of the young and are divided into castes, specialized groups that take care of certain tasks. Ants have reproductive castes, the queens and males, and nonreproductive castes, the workers.
A queen is generally the largest individual in the colony. She has wings until after her mating flight, when she removes them. The primary function of the queen is reproduction, but after establishing a new nest she may also care for and feed the first brood of workers. Once she has produced her first brood, she becomes an "egg-laying machine," cleaned and fed by her offspring. She may live for many years until replaced by a daughter queen. Some ant species have more than one queen in the nest.
Male ants are generally winged and usually keep their wings until death. Apparently, the male ant's only function is to mate with the queen. Once he does, he dies, generally within two weeks. Males are produced in old, mature colonies.
The workers are sterile, wingless females who build and repair the nest, care for the brood, defend the nest, and feed both immature and adult ants, including the queen. There may be workers and soldiers of different sizes that specialize in certain tasks.
Ants develop through a complete life cycle of egg, larva, pupa, and adult. The egg is tiny, almost microscopic in size. The larva is legless and grub-like, very soft and whitish in color. It is also helpless and depends totally on workers for food and care. The pupa looks somewhat like the adult but is soft, unpigmented, and cannot move around. Some are enclosed in a cocoon, some are not. A newly-emerged adult requires several days for its body to harden and darken.
New Colony Formation
Once a colony of ants matures, it can establish new colonies through various methods, depending on the species. The 2 most common are budding and swarming. The appropriate management strategy depends on how a colony spreads, so it is essential to correctly identify the ant species before deciding how to manage it.
Budding is the breakaway of a group of ants from a mature colony to form a new colony. The group usually consists of one or more queens and some workers carrying larvae. Budding is common with species of ants that have multiple queens, such as Pharaoh ants and Argentine ants. Residual insecticides should not be used for ants that undergo budding because they can stimulate this process.
Most ants establish new colonies through swarming. Every now and then, particularly in spring or early summer, mature ant colonies generate large numbers of winged forms. These are the young queens and males, going off to mate. An inseminated queen then rids herself of her wings and attempts to start a new nest in a cavity, under a stone or a piece of bark, or by excavating a hole in the ground. She rears her first brood alone, feeding them with salivary secretions and infertile eggs. If successful, the first brood opens up the nest and brings in food for themselves, the queen, and subsequent broods, and the colony grows. However, the percentage of queens that successfully begin new colonies is thought to be very small.
The Difference Between Winged Ants and Winged Termites
Although ants and termites are very different, they are often confused. They are alike in that they live in colonies and periodically swarm. Swarming forms of both are dark and winged. But worker termites are whitish and never seen running freely about as do ants. Instead, termites remain protected in their nests and galleries in wood and soil.
Winged adult ants can be told from winged termites by the following differences. Winged ants have a narrow waist, front wings that are larger than the rear, and elbowed antennae. Winged termites have a fat waist, equally sized wings, and straight, beaded antennae.
Most outdoor ants increase in population and activity from spring into summer months and then decline from fall into early winter as the temperature drops and the ants' natural food supplies dwindle. Other ants, such as the Argentine ant, may increase in numbers in the fall as various colonies aggregate together to overwinter. Some ants, such as the Pharaoh ant, which may live entirely indoors, exhibit little seasonality.
Knowing the food habits of the particular ant species is important in ant management because it may enable the location and elimination of the food that is attracting the ants to the site, it can help to locate foraging trails to track the ants back to their nest, and it can help to choose an effective bait.
Ants feed on many different types of food. Some species will feed on practically anything; others may limit their food to a narrow range. Ants infesting structures are typically feeding on "people food," both food in storage (sugar, cakes, cookies, breakfast cereals, etc.) and food from spills and garbage. But they may also be preying on other insects or scavenging on dead insects in windows or lights.
Food preferences are often seasonal. When the queen is actively laying eggs, worker ants typically gather protein- based foods for the queen. At other times they may ignore protein foods completely and restrict their foraging to sugars and greases.
Many ants obtain sugar by feeding on honeydew, a sweet substance secreted by aphids and other plant-sucking insects. They often defend these insects from predators and tend them as if they were their personal food supply. Indoor infestations of ants are occasionally traced to large populations of aphids on outdoor foundation plants or indoor houseplants.
MONITORING AND THRESHOLDS
Identification of the species will help to determine where the nest might be located, what the ants might be feeding on, and the best tactics for control. All parts of the building and the surrounding area should be inspected for ant activity as well as food and water sites. People that work in the building might have seen the ants also. Some species are most active in the evening. For these, a daytime inspection might discover little, while significant ant activity might be observed at midnight.
Some infestations may require an intensive survey program using nontoxic baits to determine likely nesting sites. Good baits are jelly, honey, peanut butter, bacon grease, or raw liver. The baits (or a combination of baits) should be placed on small pieces of cardboard, aluminum foil, masking tape, or plastic pill bottle lids throughout the building and periodically checked for feeding ants. Active sites should be noted on a survey diagram. Baits that haven't had any feeding activity in 24 hours should be moved. Over a period of days the survey diagram will pinpoint areas of activity. In addition, trails of ants feeding on the bait can sometimes be followed back to the nest site.
There is no single threshold level for house-infesting ants. Threshold levels need to be set separately for each site. For example, a single ant in a first-aid station may be one too many. In an eating area, control actions might be initiated if there were more than a half-dozen ants in a day, while most people's tolerance for ants in a rustic and open recreation room would likely be much higher.
NON-CHEMICAL CONTROL OF ANTS
The most effective ant control results from the destruction of the queens and the nest itself. If the nest is found by tracking workers, or through a survey, eliminating that nest is fairly simple, particularly if it is located, as it often is, outdoors, or in the soil beneath a cracked floor. It is simply a matter of mechanically destroying the nest.
But effective ant management is rarely that simple. Sometimes you can't find the nest. Often there are multiple nests. (One species, the Pharaoh ant, can have hundreds of small nests within a single room.) There may be a constant pressure from ant colonies invading from surrounding areas. In most cases, long-term management of pest ants means integrating improved sanitation, structural repairs, and habitat modification along with one or more direct control tactics such as insecticide baits, crack and crevice treatments, and direct physical controls.
Successful ant management usually requires a combination of management tactics, ranging from caulking to cleanup, improved sanitation to habitat modification, as well as targeted and limited insecticide treatment.
The keys to success in ant management are, first, vigorous inspection to determine the nature and extent of the infestation, and, if at all possible, the location of the nest. Second, meticulous sanitation to eliminate readily available food and water. Third, the choice of the right combination of tools to eliminate the problem. The listing for each ant species provides more information on management strategies relevant to that ant.
Like all pests, ants need food, water, and shelter to survive. By limiting these three essentials, you make it more difficult for ants to live in the infested area. Simply by improving sanitation you can often suppress existing populations and discourage new invasions.
Ants can enter many types of food packaging, particularly once the package has been opened. (They have even been found inside glass jars after traveling around the threads of a screw-on lid!) Cereals, sugar, and other bulk food should be stored in plastic containers with snap-on lids, in glass jars with rubber seals, or in a refrigerator.
Food spills also feed ants. As with cockroaches, enthusiastic cleaning helps to minimize ants. Frequent vacuuming, sweeping, or mopping of floors and washing of counter and table tops eliminates much of the food ants may be foraging on. Trash should be stored away from infested areas and monitored for spills.
Ants can get their water from many sources inside a structure: condensation on pipes and air conditioners, leaky plumbing, aquariums, pet dishes, houseplant containers, floor drains, etc., and limiting these is rarely practical.
Ants can enter and move through a structure through innumerable tiny cracks and openings. Yet caulking and otherwise sealing cracks and crevices being used by ants can often have great effect in suppressing the population. Many easy-to-use and effective silicon sealers and expandable caulk products have been recently developed, including some designed specifically for pest management. Repairing torn screens and installing doorsweeps can also prevent ants from easily entering a structure. Non-vegetation barriers such as stones or brick walkways next to a building can be helpful in helping to keep ants out of structures as well.
Trim the branches of trees located close to structures so the branches do not act as runways from nest sites to roof or siding. Alter landscaping to minimize the number of aphids and other honeydew-producing insects that attract ants. Firewood kept indoors should be moved outdoors or regularly inspected for ants. Don't stack wood next to structures and move trash, since ants often nest under objects. Moisture accumulation in buildings can also result in ant infestations.
Direct Physical Control
Ants can be discouraged from foraging in certain limited sites with sticky barriers. For example, commercially available sticky repellents or petroleum jelly can be applied in a narrow band around table legs to prevent ants from walking up to the tabletop. Double-sided tape can also be used.
Large numbers of worker ants can be mopped or sponged up with soapy water. Water, especially boiling water, has also been used to flood ant nests. Some ground-ant nests have been destroyed by digging them up and destroying the nest structure.
CHEMICAL CONTROL OF ANTS
Many people, on discovering ants, simply spray insecticide wherever they have seen ants. This is a poor strategy, usually doomed to failure. Applying undirected, general insecticide sprays indoors is unsatisfactory because the sprays only "harvest" a small portion of the workers and have little effect on the colony, the ultimate source of the problem. A further problem is that some species are apparently triggered into "budding" new colonies when they contact insecticide near their nests and foraging sites.
The chemical tools available for ant control have changed in the past few years with the addition of insect growth regulators, new baits, and commercial bait stations, and new tools can be expected in the future. Even so, insecticides are only one of the tools available for control of ants, and not always the best or most important. Ant biology should be considered when deciding whether or not to use insecticides. For example, insecticides are often not effective against mound ants because it often takes foraging ants several days to return to the nests. Consult your regional National Park Service Integrated Pest Management coordinator for information on using pesticides as part of an ant management program.
The best baits for ants are those whose toxicant kills ants slowly. In this way, worker ants live long enough to take the baits back to the nest and feed it to the colony and queen. A number of baits are now available. Some are prepackaged in child-resistant bait stations. Some are gels or pastes designed to be placed in small pea-shaped amounts throughout an area. Some products (such as boric acid) are designed to be mixed with a food. Bait products typically will work against certain species of ants but not against others, so it is important to check the label to make sure the ant you wish to control is listed.
Insect growth regulators (IGRs)
These are available in bait form for some ant species. Insect growth regulators inhibit normal development of insects. They are slow-acting because they stop the next generation from developing rather than killing the current generation. A recent study comparing the insect growth regulator fenoxycarb to a commercial bait found that the growth regulator was more effective than the bait in eliminating Pharaoh ants. This is most likely because the bait kills ants too quickly to be effectively distributed throughout the colony (Williams and Vail 1994). Crazy ants do not seem to respond well to bait, and baits may be slow-acting against field ants since they often stay away from the nest for several days.
Liquid and aerosol insecticides
Nearly all of the insecticides labeled for use against cockroaches are also labeled for use against ants. These insecticides are most effective when used to treat actual nest sites. Insecticides are less effective, but still may provide acceptable results when used to treat inside cracks and crevices used by ants in and around infested sites. They are least effective, as well as offering the highest potential of human exposure, when they are simply applied to sites where activity has been observed.
For certain ground-nesting ants that dig deep nests outdoors, a soil drench or mound drench can be effective where other treatments are not. As its name implies, a soil drench consists of applying enough insecticide dilution directly to a mound or nest so that the entire nest is drenched.
Dusts may also be used on occasion for ant control if they are used lightly or directed into nests. In large amounts, dusts tend to repel ants. But they have the advantage of floating back through wall voids to reach nests that may not be accessible with other formulations.
Granules are rarely used in household ant control. They may be useful, however, when a lawn or field is heavily infested with many colonies of a shallow, ground- nesting species of ant.
Argentine Ants ~ Carpenter Ants ~ Crazy Ants ~ Field Ants
Fire Ants ~ Pavements Ants ~ Pharaoh Ants ~ Thief Ants
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