Pharaoh ant
Pharaoh ant | |
---|---|
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Arthropoda |
Class: | Insecta |
Order: | Hymenoptera |
Family: | Formicidae |
Subfamily: | Myrmicinae |
Genus: | Monomorium |
Species: | M. pharaonis
|
Binomial name | |
Monomorium pharaonis (Linnaeus, 1758)
| |
Synonyms | |
Formica pharaonis |
The pharaoh ant (Monomorium pharaonis) is a small (2 mm) yellow or light brown, almost transparent
This species is polygynous—each colony contains many queens—leading to unique caste interactions and colony dynamics. This also allows the colony to fragment into bud colonies quickly.
Pharaoh ants are a tropical species, but they also thrive in buildings almost anywhere, even in
Physical characteristics
Pharaoh workers are about 1.5–2.0 millimetres (1⁄16 in) long. They are light yellow to reddish brown in color with a darker
Males are about 3 millimetres (1⁄8 in) long, black, winged (but do not fly). Queens are dark red and 3.6–5.0 millimetres (1⁄8–3⁄16 in) long. They initially have wings that are lost soon after mating, but do not fly.[7]
Life cycle
The pharaoh ant queen can lay hundreds of eggs in her lifetime. Most lay 10 to 12 eggs per batch in the early days of egg production and only four to seven eggs per batch later. At 27 °
Colony proliferation
Each colony produces sexually reproductive individuals roughly twice a year. However, colonies raised in a laboratory can be manipulated to produce sexuals at any time of year. Colonies proliferate by "budding"[3] (also called "satelliting" or "fractionating"), where a subset of the colony including queens, workers and brood (eggs, larvae and pupae) leave the main colony for an alternative nest site.
Pharaoh ant colonies appear to prefer familiar nests to novel nests while budding. This suggests the ability for colonies to remember certain qualities of their living space. However, if the novel (unfamiliar) nest is of superior quality, the colony may initially move toward the familiar, but will eventually select the unfamiliar. The colony assumes the familiar nest is preferable, unless they sense better qualities in the novel nest. This decision-making process seeks to minimize the time the colony is without a nest while optimizing the nest the colony finally chooses.[8]
The number of available budding locations has a large effect on colony fragmentation. A large number of bud nests results in small colony fragments, indicating that the colony has the ability to control size and
In
Pheromones
Pharaoh ants utilize three types of
Both the attractive and repellent pheromones are utilized in the decision-making an ant must make while foraging. The repellent pheromone is especially useful in the repositioning of trails after a new food source has been introduced. It also helps prevent ants from concentrating on an undesirable trail. Thus, the repellant pheromone makes the pharaoh ant a particularly efficient forager.[14] Despite their extreme importance, there is an adaptive value to using pheromones sparingly, as it streamlines communication during important decision-making situations, such as a nest migration.[15]
Foraging
Pharaoh ants use a positive feedback system of foraging. Each morning, scouts will search for food. When one finds it, it will immediately return to the nest. This causes several ants to follow the successful scout's trail back to the food source. Soon, a large group will be upon the food. Scouts are thought to use both chemical and visual cues to remain aware of the nest location and find their way.[16] If the colony is exploring a new region, they employ a land rush tactic, in which a large number of foragers randomly search, constantly releasing pheromones.[11]
Even though M. pharaonis is most often thought an indoor pest, foraging has been found to be more prevalent outside. Even inside colonies were found to forage close to windows, indicating a propensity for outdoor environment.[1]
Trails
Even though scouts search independently, they use a distinct trail system that remains somewhat constant from day to day. The system consists of one to four trunk routes. Every scout uses one of these trunks in the beginning and end of its food search. In this way, the trunks get continuous chemical reinforcement and do not change much. Each trunk divides into many branch routes. These will change based on food availability.[16]
The organization of foraging trails is strongly affected by the health of the colony and the availability of food. Food deprivation induces a higher amount of foraging ant traffic, compared to a non-deprived population. If a food source is presented to the food deprived colony, this traffic was further increased, an indication of the pharaoh ant's recruitment tactic. If food is not present, a colony will extend its trails to a wider radius around the nest. Logically, number of trails and forager traffic is largest near a food source.[17]
While pheromones explain the pharaoh ant's foraging ability, each forager's capability to find its way back to the nest requires a different explanation. In fact, the pharaoh ant relies on geometry to show it the way home. Each fork in the trail system spreads at an angle between 50 and 60 degrees. When returning to the nest, a forager that encounters a fork will almost always take the path that deviates less from its current direction. In other words, it will never choose an acute angle that would drastically change its direction. Using this algorithm, each forager is able to find its way back to the nest. If the fork angle is experimentally increased to an angle between 60 and 120 degrees, M. pharaonis foragers were significantly less able to find their nest. This method of decision-making reduces the wasted energy that would result from traveling in the wrong direction and contributes to the pharaoh ant's efficiency in foraging.[18]
Feeding
Upon scouts' return with food, the queens will attempt to beg for their share. Depending on food availability and each individual's condition, a scout may refuse the queen's entreaties and even run away from her.[19] The decision of an individual to give up food to the queen may be beneficial in situations of plentiful food, as a healthy queen can reproduce and propagate the colony's genes. However, when food is highly scarce, an individual's own survival can outweigh this potential benefit. She will therefore refuse to give up food.
A queen may also feed on secretions from larvae. This creates a positive feedback loop in which more larvae will provide more food to queens who can in turn produce more larvae.[20]
If a large amount of larvae results in a surplus of secretions, pharaoh ants will store the excess in the gasters of a unique caste, the replete workers. Members of this group have enormous gasters and can regurgitate their stored food when needed. In this way, the colony has a cushion against food shortages.[21]
Pharaoh ants have a sophisticated strategy for food preference. They implement two related behaviors. The first is known as satiation. The workers will at first show a strong preference for a particular food type. However, if this food is offered alone, with no other options, for several weeks, workers will afterward show a distinct preference for a different type of food. In this way, the ants become satiated on a certain food group and will change their decision. The second behavior is called alternation. If given the continuous choice between food groups, pharaoh ants will tend to alternate between carbohydrate-rich foods and protein-rich foods. These satiation and alternation behaviors are evolutionarily adaptive. The decision to vary the type of food consumed ensures that the colony maintains a balanced diet.[22] Edwards & Abraham 1990's result is appropriate for highly competitive environments, and consistent with a high intake:expenditure ratio.[23]
Caste system
Monomorium pharaonis, similar to other invasive ants, is
Many invasive ants display unicoloniality. The
Pharaoh ant colonies contain many queens. The ratio of queens to workers is variable and dependent on the size of the colony. An individual
Nest demographic
The Pharaoh ant is a polygynous species that has a relatively low worker to queen ratio of around 12.86. This allows the pharaoh ants to be able to exert social control over the size of the colony and the size of each caste. In the average nest, there are around 170 ± 8 queens, which comprises around 5.2% of the total population, whereas there are around 2185 ± 49 workers, which make up around 66.6% of the population. This low worker to queen ratio is usually associated with swift changes in the nest and may be why pharaoh ants form many new nest buds quickly.[27] To branch out and form a new bud nest, pharaoh ants need a minimum of 469 ± 28 individuals, which explains how they proliferate so quickly.[28]
Reproduction
Mating for pharaoh ants occurs within the nests with males that are usually not from the colony which ensures genetic diversity. The queen can typically produce eggs in batches of 10 to 12 at once, but can lay up to 400 eggs every time she mates. The eggs that are produced take up to 42 days to mature from an egg to an adult. Each queen within the nest lives between 4 and 12 months.[29]
During copulation, sperm is transferred from male to female inside a spermatophore. There are several theories regarding the adaptive value of using a spermatophore. It contains certain chemicals that may inhibit the female's sex drive. Alternatively, it may physically plug the female's gonophore. In either explanation, the spermatophore prevents the female from reproducing with another male. In essence, the use of a spermatophore is evolutionarily favorable because it increases the probability of the male's genetic code being transferred to subsequent generations by lessening potential competition from other males.[30]
Pharaoh ant copulation, like that of many social insects, is harmful to the female. The penis valve contains sharp teeth, which latch onto a thick, soft cuticular layer in the female. This method of copulation too has an evolutionary basis. The teeth ensure sex lasts long enough for sufficient sperm transfer. Also, the pain caused to the female may, in some ways, lessen her desire to mate again.[30]
Queen–worker relationship
When the queen ant first moves to a new nest, she will rear the first group of workers. Once a worker threshold has been reached, resources will then be invested into new males and queens. When a new nest is formed, queens are not a necessity; workers can raise new queens after finding a suitable nest site.[25][28]
In pharaoh ant colonies new males and queen ants can be produced when the existing fertile queen is removed. When queens are absent, the workers in the nest can do two things: either rear existing sexual larvae or transport sexual larvae from other bud nests or from the main nest to its own nest. However, when there are fertile queens still within the nest, the worker ants will cannibalize the sexual larvae and will either reject or consume sexual larvae from other nests. On the other hand, the worker ants will always accept and nurture worker larvae from other nests.[26][31] Furthermore, according to Schmidt et al., polygamous species such as pharaoh ants will have higher resource allocations towards the female caste instead of the worker caste to ensure rapid growth of new budding colonies.[25]
Colony interaction
When social ants encounter ants from another colony, behavior can be either aggressive or non-aggressive. Aggressive behavior is very commonly seen; the attacking worker usually bites the opponent at the
Washing
After foraging, pharaoh ants will wash themselves when a worker enters the cell. Pharaoh ants will also wash after a long feed. It has been proposed that washing has a hygienic value, keeping the nest area clean, staving off disease and disorder. Right before workers leave to forage, they also may wash themselves. However, in this instance the behavior is extremely violent, often causing the ants to fall over. It is thought that here, the washing behavior has no hygienic value and instead may be a displacement activity, a sign that the ants are deliberating whether or not to exit the nest.[19]
Invasiveness and extermination
Budding is a major factor underlying the invasiveness of pharaoh ants. A single seed colony can populate a large office block, almost to the exclusion of all other insect pests, in less than six months. Elimination and control are difficult because multiple colonies can consolidate into smaller colonies during extermination programs only to repopulate later.
Pharaoh ants have become a serious pest in almost every type of building. They can feed on a wide variety of foods including grease, sugary foods, and dead insects. They can also gnaw holes in
It is recommended not to attempt extermination using insecticidal sprays and dusts because they will cause the pharaoh ants to scatter and colonies to split, although non-repellent residual insecticides have been reported to be effective.[33]
The recommended method to eliminate pharaoh ants is by the use of
Pharaoh and other ants have also been exterminated with baits of 1% boric acid and sugar water.[34]
See also
- Argentine ant, another known pest species
References
- ^ JSTOR 3495874.
- ^ a b c Pharaoh Ant control
- ^ a b c d Pharaoh Ant Elimination
- ^ "Pharaoh ant". Entomology and Nematology Department of the University of Florida. Retrieved 25 March 2024.
- ISBN 978-0-8014-7473-6. Retrieved 15 August 2013.
- ^ "Cranbrook Pest Control". Pharaoh Ant. Cranbrook Pest Control Ltd. Retrieved 12 November 2013.
- ^ "Pharaoh Ant". Bayer Environmental Science - Pest Management. Retrieved 10 April 2019.
- S2CID 15455885.
- .
- S2CID 29657887.
- ^ PMID 15351134.
- ^ S2CID 27760894.
- PMID 16306981.
- PMID 18778716.
- S2CID 53170114.
- ^ .
- ^ Fourcassié, V.; J. Deneubourg (1992). "Collective exploration in the ant Monomorium pharaonis L.". Biology and Evolution of Social Insects: 369–373.
- ^ "Angles Show Ants the Way Home". New Scientist. 184 (2478): 19. 18 December 2004.
- ^ .
- S2CID 20349419.
- S2CID 31953751.
- S2CID 28423022.
- S2CID 52846073.
- ^ PMID 20591186.
- ^ S2CID 22208239.
- ^ S2CID 83671992.
- .
- ^ S2CID 13004419.
- ^ Peacock AD, Hall DW, Smith IC, Goodfellow A. 1950. The biology and control of the ant pest Monomorium pharaonis (L.). Department of Agriculture of Scotland Miscellaneous Publications 17. 51 p.
- ^ S2CID 84683592.
- S2CID 11357438.
- .
- ^ ISBN 978-92-890-7188-8.
- .
External links
- Picture of a M. pharaonis
- Ohio State University Extension Fact Sheet at archive.today (archived 2001-04-25)
- Pharaoh ant on the UF / IFAS Featured Creatures Web site