Carpenter ants are a common nuisance for homeowners, not because they pose a direct health risk, but due to their potential to cause significant structural damage. These insects don't consume wood as a food source; instead, they excavate it to create nests, which can compromise the integrity of wooden structures. Understanding their diet and habits is crucial for effective prevention and control.
What Carpenter Ants Eat: An Overview
Carpenter ants are omnivores, meaning their diet consists of both protein and carbohydrates. Their food preferences can vary depending on the season and the needs of the colony.
Protein Sources
Protein is essential for the growth of larvae and the overall health of the colony. Carpenter ants obtain protein from:
- Insects: They eat both dead and living insects, making them natural competitors with termites.
- Dead Animals: They scavenge on dead animals as a source of protein.
Carbohydrate Sources
Carbohydrates provide energy for adult workers. Carpenter ants are attracted to:
- Honeydew: This sugary substance is produced by aphids and scale insects, and it serves as a primary food source in their natural environment.
- Plant Nectars and Fruit Juices: Carpenter ants also consume plant nectars and fruit juices.
- Sugary Foods: Inside homes, they seek out sugar, honey, jams, jellies, syrups, and other sweet items.
Debunking the Myth: Carpenter Ants Don't Eat Wood
A common misconception is that carpenter ants eat wood like termites. However, carpenter ants do not digest wood. They excavate wood to create galleries and tunnels for their nests. This excavation process results in piles of sawdust-like shavings, which are a telltale sign of their presence.
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Seasonal Variation in Diet
Carpenter ants' dietary needs change throughout the year:
- Spring: During the spring, the colony requires more protein to support the queen's egg-laying and the development of larvae.
- Summer and Fall: Adult workers need energy for foraging, so they shift their preference towards carbohydrates and sugars.
What Attracts Carpenter Ants to Your Home?
Carpenter ants typically nest outdoors in dead trees or stumps. However, they may move indoors in search of food, water, or nesting sites. Several factors can make your home attractive to them:
- Moisture: Damp or rotting wood is particularly appealing for nesting, as it is easier to tunnel through. Areas with water leaks, condensation, or poor air circulation are prime targets. Moist drywall is an ideal nesting place for Carpenter Ants.
- Food Sources: Accessible sugary substances and protein sources can draw them indoors.
- Access Points: Foliage or branches touching the house can serve as "skywalks" for ants to gain entry.
Identifying a Carpenter Ant Infestation
Recognizing the signs of a carpenter ant infestation is crucial for early intervention:
- Sawdust Piles: These piles, resembling wood shavings, are left behind as ants excavate wood. They can be found near the base or branches of trees, as well as inside the home.
- Rustling Sounds: Faint rustling or crunching sounds inside walls or ceilings, especially when tapping the surface, may indicate ant activity.
- Visible Ants: Carpenter ants are large, typically black or reddish in color, and range from 1/4 to 1/2 inch long. They are most active at night.
- Galleries in Wood: Tunnels created by carpenter ants are smooth and clean, resembling sandpapered surfaces.
- Winged Ants: The presence of winged carpenter ants indoors is a sure sign that a nest exists inside your home.
Finding the Nest
Locating the nest is essential for effective control. Here are some tips:
- Follow Ant Trails: Observe foraging trails to trace their movements back to the nest. Carpenter ants often travel along consistent paths when searching for food.
- Check for Moisture: Examine areas where moisture is or has been a problem.
- Listen for Sounds: Listen for rustling sounds inside walls or ceilings.
Managing Carpenter Ant Infestations
An integrated pest management (IPM) approach is recommended for long-term control:
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- Inspection: Thoroughly inspect the property to identify the extent of the infestation and locate nests.
- Fixing Conditions: Address moisture issues by repairing leaks, improving ventilation, and removing sources of standing water.
- Exclusion: Seal cracks and gaps in the foundation, walls, and around pipes to prevent ants from entering the home.
- Targeted Treatments: Baits can be effective for controlling carpenter ants. They contain a slow-acting ingredient that workers carry back to the nest, eventually eliminating the entire colony. Non-repellent products are also recommended.
- Professional Assistance: If nests are hard to find or the problem is widespread, it's wise to call professionals.
Baiting Carpenter Ants
Baiting carpenter ants is possible using both natural and artificial means. The simplest way to get an idea of the location of ant nests is to look for places with damp wood, which is nothing less than a goldmine for carpenter ants. You can also look for piles of sawdust. The best method is to follow a few ants back to their nests in the evening when they are the most active.
A natural carpenter ant bait can be made by mixing equal quantities of baking powder and sugar. As baking powder is a natural poison to ants and sugar an attraction, ants will be killed when they consume the mixture.
Preventing Carpenter Ants
- Maintain your property: Regularly inspect and maintain your home to prevent moisture damage and eliminate potential nesting sites.
- Store food properly: Store food in airtight containers and clean up spills immediately.
- Trim vegetation: Keep trees and shrubs trimmed away from the house to prevent ants from using them as access points.
- Remove dead wood: Remove dead trees, stumps, and wood piles from your property.
Carpenter Ants and Their Endosymbiotic Relationship
Carpenter ants (genus Camponotus) are considered to be omnivores. Nonetheless, the genome sequence of Blochmannia floridanus, the obligate intracellular endosymbiont of Camponotus floridanus, suggests a function in nutritional upgrading of host resources by the bacterium. Nutritional upgrading by Blochmannia was tested in 90-day feeding experiments with brood-raising in worker-groups on chemically defined diets with and without essential amino acids and treated or not with antibiotics. Control groups were fed with cockroaches, honey water and Bhatkar agar. Worker-groups were provided with brood collected from the queenright mother-colonies (45 eggs and 45 first instar larvae each).
Brood production did not differ significantly between groups of symbiotic workers on diets with and without essential amino acids. However, aposymbiotic worker groups raised significantly less brood on a diet lacking essential amino acids. Reduced brood production by aposymbiotic workers was compensated when those groups were provided with essential amino acids in their diet. Decrease of endosymbionts due to treatment with antibiotic was monitored by qRT-PCR and FISH after the 90-day experimental period. Urease function was confirmed by feeding experiments using 15N-labelled urea. Our results show that endosymbiotic Blochmannia nutritionally upgrade the diet of C. floridanus hosts to provide essential amino acids, and that it may also play a role in nitrogen recycling via its functional urease. Blochmannia may confer a significant fitness advantage via nutritional upgrading by enhancing competitive ability of Camponotus with other ant species lacking such an endosymbiont.
Insects are among the most successful animal taxa in respect to species richness as well as abundance. Their evolutionary success is in part facilitated by obligate intracellular bacterial endosymbionts that enable some insect groups to live on nutritionally deficient diets and thus in ecological niches that may otherwise be unavailable. Buchner [1] estimated that approximately 20% of all insects harbour intracellular endosymbiotic bacteria. Such insect hosts are usually food specialists [2] with the bacteria supplying essential nutrients that are deficient in the host's diet. For example, aphids that feed exclusively on phloem sap are provided with essential amino acids by Buchnera [3], and Wigglesworthia supplies blood-feeding tsetse flies with certain vitamins that are deficient in the diet [4,5]. In these ways, endosymbionts upgrade host nutrition by utilizing constituents of the host's food to synthesize compounds that are of higher nutritional value to the host. Usually, either non-essential food constituents are transformed into compounds essential to the host, or compounds that cannot or are poorly metabolized by the host itself are utilized by the bacteria. Although less well documented, endosymbionts may also facilitate life in nutrient-limited niches for insects that are more generalist feeders.
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Carpenter ants (genus Camponotus) harbour the obligate intracellular endosymbiont Blochmannia in bacteriocytes, intercalated between midgut cells, as well as in ovaries of females [6,7]. With more than 1000 species, Camponotus is among the most species-rich and successful genera of ants [8], and is represented in most terrestrial habitats, including among dominant ants of tropical rain forest canopies [9,10]. Suggesting functional importance for the genus as a whole, Blochmannia has been detected in all Camponotus species investigated to date (> 30 species), including taxa from various different parts of the genus [7,8,11,12]. In addition to Camponotus, the bacteria were recently also identified in the related genera Polyrhachis, and Echinopla, all belonging to the subfamily Formincinae, tribe Camponotini [11,13] and Feldhaar, unpublished results, for ~16 species of Polyrhachis). The appearance of Blochmannia in closely related genera within the ant subfamily Formicinae suggests an age of the endosymbiosis of approx. 30 to 40 MYA (million years ago) [13,14].
The metabolic capacities of Blochmannia floridanus and Blochmannia pennsylvanicus, the two endosymbiont species sequenced so far, show remarkable similarity to that of Buchnera, the aphid endosymbiont, in their genetic make-up. The genome of Blochmannia is strongly reduced in size in comparison to those of its free-living ancestors [15,16] and strongly adenine-thymine-biased. Despite such strong reduction in genome size, biosynthetic pathways for essential amino acids (except arginine) are retained, while those for several non-essential amino acids have been lost [15-17]. Blochmannia can apparently synthesize tyrosine, a non-essential amino acid that, together with the essential phenylalanine, is important for tanning and sclerotization of insect cuticle [18]. Accordingly, upregulation of tyrosine biosynthesis genes of the endosymbiont was detected during the pupal stage of hosts and Blochmannia may thus supplement the host with tyrosine [19]. Blochmannia may also play a role in sulfate reduction to sulfide, a form of sulfur that can be incorporated into biomolecules [17]. Insects themselves are generally unable to reduce oxidized sulfur compounds [20]. Additionally, the ant-endosymbiont contains a complete urease gene cluster. This enzyme hydrolyzes urea to produce CO2 and ammonia, and ammonia can then be recycled into the host's amino acid metabolism by the activity of glutamine synthetase, also encoded by Blochmannia [17]. In some pathogenic microorganisms, ureases have been identified as important virulence factors [21,22] whereas the urease may be beneficial for the host in this symbiotic association.
The aim of this study is to gain insight into the mechanisms of the endosymbiont-host interaction by testing in vivo functions predicted from Blochmannia's genome. Genome sequence alone is not an infallible predictor of the endosymbiont's role in symbioses; for example, the same strain of the obligate intracellular bacterium Wolbachia confers different fitness benefits depending on its host's genetic background [23]. In addition, for endosymbionts to be involved in interactions with the host, the respective genes must be functional. Endosymbiont genes not under stabilizing selection should deteriorate, and even those needed by insect hosts may be lost, possibly leading to a loss in the symbiotic function of the endosymbiont [24]. This process starts with gene inactivation producing a pseudogene, and only then are major parts of the gene lost from the genome, a process that may take over several million years [25,26]. The general relevance of Blochmannia for the ant host is apparent from fostering experiments showing that colonies of C. floridanus suffer serious fitness losses when workers are cured of infection with Blochmannia. To specifically test whether Blochmannia affects host metabolism, we developed a chemically defined diet that allows for omission of specific nutrients [28]. We then tested the hypothesis that Blochmannia provides the host with essential amino acids.