[Wood-Destroying Ants] Captivating Crunchers

Industry veteran Norm Ehmann’s reflections on the carpenter ant, a fascinating pest that is also a widespread nuisance.

February 19, 2009

Editor’s note: The following information on carpenter ants has been excerpted from Norm Ehmann’s book “Adventures Through The World of Entomology.” The book blends technical information with gritty, down-to-earth knowledge geared to everyone from seasoned veterans to the industry’s newest workers and can be ordered from Univar reps at 800/808-4897 or online at www.pestweb.com.

There are well over 1,000 different species of carpenter ants worldwide. Here in the United States the professional structural pest control service technician is concerned with less than a half dozen species — three of which are capable of causing severe structural damage and two of which are merely an annoyance because of their presence in homes. Have you ever been out hiking in the hills or the mountains and, becoming tired, sat down on a log to rest? If you were almost immediately bothered by a number of big black ants, the chances are good that you were sitting on a carpenter ant home since carpenter ants perform the function in nature of helping return the fallen trees of the forest to compost. Wood-boring beetles, termites, and various types of fungi help them in this endeavor. The black carpenter ant, Camponotus pennsylvanicus, is the most common carpenter ant in the eastern United States, and is responsible for a large amount of structural damage.

The most common species along the West Coast of the United States is Camponotus modoc and the second most common species on the West Coast is Camponotus vicinus. Both of these species are large black ants with red legs. Both of these species do a major amount of damage to wooden structures. In the state of Washington, for example, Camponotus vicinus causes more structural damage to homes than any other pest, including termites. Camponotus floridanus is found in Florida. It has a very light reddish head and thorax with a somewhat darker reddish abdomen. The Hawaiian carpenter ant, Camponotus variegates, which was brought into Hawaii from Southeast Asia, is a very pale yellow-brown colored ant.

CHECK ALL VOIDS. When making an inspection for any of the following five key ant species — carpenter, Argentine, pharaoh, red imported, and harvester  — it is important to keep the concept of a “void” clearly in mind, and if the void is close to a source of moisture the chances of finding a secondary “nest”  are enhanced.

For instance, homes frequently have hollow sliding doors between rooms. These doors slide into the wall space when not being used. The doors are hollow with diagonal bracing inside. The trick is to knock on the door and then put your ear up to it and listen. If it is infested with carpenter ants you will hear a frantic rustling noise caused by the ants that were disturbed by the knocking on the outside of the door. Another common habitat for carpenter ants is the space available in tongue and groove ceilings. These are just two examples of a void space readily available to the carpenter ant. There are many more in the average home. Remember, when inspecting, think “void spaces.”

SECONDARY NEST. The term “secondary nest” was previously mentioned. Let’s talk about the function of a secondary nest. First, we need to understand that the primary nest of the carpenter ant is almost always outdoors (e.g., in an old tree stump, or in a hole left when a branch broke off a tree, or in a fence post, or other substantial mass of cellulose material). This primary colony may be as far away from the house as 500 feet. Ants from the primary colony then make their way into the home by leaving a pheromone scent trail for other ants to follow. In an infestation that has been established for some time the incessant traveling to and from causes a path to be worn away like a deer trail, only much smaller. A well trained technician can spot such trails in a lawn area and can follow the foraging ants from the house back to the primary nest (sometimes). If conditions in the home are favorable, that is, if there is a suitable void available and enough food present, a secondary or satellite nest may be established and larvae and pupae are carried from the primary nest to this secondary nest to be taken care of at this location until they reach the adult stage.

Ants in general have a complete life cycle consisting of egg, larva, pupa and adult. Some species of ants will have many (100 more) reproductive members in the primary colony, but carpenter ants usually have only one queen per colony. (There are exceptions to this rule). The queen, in starting a colony, lays a few eggs that hatch into larvae, which she feeds by regurgitating into their mouths — the breakdown products of her wing muscles. These few larvae pupate and turn into small-sized adult worker ants, called “minims,” that sally forth to forage for food to feed the queen and any subsequent larvae that hatch from the second batch of eggs. The queen at this point is an egg-laying machine and her sole function for the rest of the life of the colony is producing eggs. Some species of ants are polymorphic and some are not. Being polymorphic means that the worker ants that are produced can be of several sizes. The small ones are known as minims that, once a colony is established, usually stay inside of the colony to care for the queen and to feed larvae that hatch from the eggs. The medium-sized ants usually are the workers that forage for food for the rest of the colony. They regurgitate this food to the minims who in turn feed it to the larvae. The large worker ants usually function as the soldiers of the colony, defending it from intrusion by the other species of ants and predators. The size of each ant is determined by what it is fed in the larval stage. Once it has pupated and becomes an adult it does not increase in size, but maintains its status as either a small, medium, or large ant. A general rule is that only about 10 percent of the members of a colony are out foraging for food at any one time. The medium-sized ants that are not foraging for food at any given time are put to work caring for larvae and pupae and also enlarging the size of the “nest.”

HOW THEY DO DAMAGE. Carpenter ants do not eat wood. As they tunnel their way through the wooden structures in the home they carve off a piece of wood with their mandibles and cast it aside as refuse. When the chambers they are in get too full of  refuse, they bore a slit to the outside world and push the refuse out of the chamber (that could be called housecleaning). The refuse falls to the ground or to the floor of the home or to the sill plate where it stacks up into mounds. It is these mounds that the service technician looks for during his inspection because they help locate the site of the colony. Carpenter ants crush other insects and lap up their body juices. Thus, the body parts of food insects (legs, etc.) also pile up in the chambers of the carpenter ant and are pushed out along with wood chips. When the service technician sees a pile of wood chips containing insect parts, he knows that there are some carpenter ant galleries in the wood close by and directly above the pile of “sawdust.”

Secondary nests can occur in any void space in a house or in any galleries that worker ants have carved out. If there is a moisture condition caused by a leaky pipe, or malfunctioning roof gutter, or any other cause of moisture, it is probable that the secondary nest will be located in or next to that affected area. Larvae and pupae, but no eggs will be found in the secondary nest. Forager ants operate out of a secondary nest, but contact always is maintained between the primary and the secondary, or satellite nest.

Carpenter ants forage at night and they love sweets. Many times carpenter ants are first seen by the homeowner while he or she is watching television in the evening.  Suddenly they become conscious of a line of large black ants marching along the trim board at the ceiling level. That’s when the pest control operator gets a call. A more urgent call comes in when the alates (winged adult male and female ants) swarm out of the secondary nest and toward the nearest light source. This may be a window during the day or a reading lamp at night or even the television itself. Besides being attracted to sources of sweets inside of the house, carpenter ants also attend aphids and other insects that secrete honeydew on plants and trees outside the house.

Successful control measures should include finding and destroying the primary nest, thus knocking the egg-laying queen out of commission.

CONCLUSION. You’d be hard pressed to find structures in the U.S. that are considered safe from possible carpenter ant infestations. Because so many species of carpenter ants are found throughout the U.S., this ant is perhaps the most significant structure-infesting ant species. Treating a home infested with carpenter ants can be challenging, but it also provides pest management professionals with an opportunity to prove themselves as true protectors of property.

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