Linepithema humile

Geographic Range

Argentine ants ( Linepithema humile ) are a significant invasive species across the globe. They are native to the Neotropical region, originating in South America; they are still widespread across the region. Since the late 1800s, they have been spreading due to human commercial activities, primarily to regions with a Mediterranean climate. They are now found on all continents except Antarctica and some Oceanic islands. Their range is restricted by temperature; they typically cannot survive in areas with a mean daily temperature below 7 to 14 degrees Celsius. In the United States, North Carolina and California are the northern most edges of their range; they are much more common in coastal regions than in the interior of the country. They can be found across much of Europe, including the Iberian peninsula, France, and of course, the Mediterranean. They are also significant in Japan, South Africa, New Zealand, and Australia.

• Biogeographic Regions
• nearctic nearctic
  • introduced introduced
• palearctic palearctic
  • introduced introduced
• oriental oriental
  • introduced introduced
• ethiopian ethiopian
  • introduced introduced
• neotropical neotropical
  • native native
• australian australian
  • introduced introduced
• oceanic islands oceanic islands
  • introduced introduced

Habitat

Argentine ants are able to survive in a variety of habitats, limited only by temperature and water sources. They are able to survive in temperatures from -5 to 45 degrees Celsius, though they typically cannot thrive in areas with a mean daily temperature below 7 to 14 degrees Celsius. Water sources are also key to these ants, including natural sources such as rivers and man-made sources such as urban water runoff. Colonies nest in forests, agricultural fields, shrublands, fields, near rivers, and in other areas disturbed by human activity. Nests are also prevalent in urban and suburban areas, as these ants can invade homes and other buildings. Nests are shallow, typically no more than 1 to 2 inches into the soil. Argentine ants also nest under wood and debris, in sandy soil, under rocks, in cracks in pavement, and in buildings.

• Habitat Regions
• temperate temperate
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• savanna or grassland savanna or grassland
• forest forest

• Other Habitat Features
• urban urban
• suburban suburban
• agricultural agricultural
• riparian riparian

Physical Description

Argentine ants are a small species of ants, with 1 petiole, a short, robust thorax, a flattened head, and slender legs. Workers are typically around 0.3 mm in length, unlike other ant species; all workers are the same size. Workers weigh about 0.43 mg. Males are about the same size or a little larger than workers, weighing about 1.0 mg, while sexual females (also known as queens) are significantly larger, measuring 4.5 to 5.0 mm in length and weighing about 3.6 mg. All ants of this species are dull brown, though males and queens are usually darker than workers. Their coloration is uniform across their body, though small body parts, such as mandibles and antennae can have 3 different shades. Workers have yellowish mandibles and their legs are a lighter shade of brown than their body. Sexual females have yellow mandibles and reddish legs and antennae, while males have yellowish legs, antennae, and mandibles. Sexual females are also more opaque than workers, with more hairs on their body. Males have wings throughout their adult lifespan, while sexual females lose their wings after mating.

Their eggs are pearly white and elliptical in shape. Their mean size is 0.3 mm long by 0.2 mm wide and they weigh about 0.02 mg. The surface of their eggs becomes dull when they are nearly hatched. Newly hatched larvae are about 0.5 mm long and grow to about 1.7 mm, though male larvae can grow to 2.5 mm in length. Larvae are white and curved, straightening as they develop and grow. They weigh 0.1 to 0.5 mg. Queen larvae are matte and opaque in appearance and can be easily distinguished from the shiny larvae of workers and males. Pupae are naked but their features are visible. While three forms can be differentiated, all are white after pupation and transition through several shades of cream and brown until they reach a similar shade as adult ants. Worker pupae are about 2.0 mm long, with a prominent head that is about 50% of their length and noticeably visible eyes. Male pupae are about 3.0 mm long, with a large thorax. Queen pupae are much larger than either male or worker pupae, with prominent wing pads and proportionate body parts.

• Other Physical Features
• ectothermic ectothermic
• heterothermic heterothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• female larger

Development

Argentine ants are holometabolous. Eggs are laid from early spring to late fall and hatch after about 28 days, though incubation can last from 12 to 55 days. During the first 5 days after hatching, larvae grow rapidly; their development takes 11 to 61 days, with an average of 31 days. Workers pupate for an average of 20 days, males pupate for 19 to 28 days, and queens pupate for 2 to 4 weeks. Development is faster at warmer temperatures. Prior to adulthood, their legs, mouth parts, and antennae become prominent, workers help remove the pupal skin and straighten the body parts. During this stage, known as the callow stage, newly molted ants look like all other adults except they are colorless and clumsy, staggering around. After 48 to 72 hours, the ant is a fully functioning adult. At least 33 days are needed to develop into an adult, though 74 days seems average. The first batch of eggs, typically laid in early spring, develop into the sexual brood, present in the nest by late spring or early summer. Eggs laid later in the season develop into workers. Gyne and worker production depends on the presence of queens and the pheromones they produce. The worker population peaks in late summer and fall and brood production decreases steadily in late fall.

• Development - Life Cycle
• metamorphosis metamorphosis

Reproduction

Argentine ants mate in the nest during late spring and summer. Prior to mating, males may join in a nuptial flight, though queens remain in the nest. Males may return to their original nest or join a new nest. If males join a foreign nest, they may face some aggression from workers, though aggression changes throughout the season. If alate females are present in the nest, workers are significantly less aggressive towards foreign males. Mating takes place a few days after eclosion. After about 6 minutes and after sperm transfer has occurred, a female will bite her male mate, initiating the end of copulation. On rare occasions, the female's bite may actually kill the male. Other males may fight over females and disturb other mating pairs, likely decreasing the amount of sperm transferred. Mating pairs can be seen moving to new locations to avoid these disruptive males. Females are only inseminated by one male, though they may mate with several males. Males can inseminate several females, but often discharge all of their sperm during one insemination. Males die shortly after mating, while queens do not lay eggs until the following spring, if they survive until then. Workers are completely sterile and do not mate. Since nuptial flights allow for dispersal and also prevent inbreeding, it is interesting that Argentine ants mate in the nest. Studies have shown that inbreeding does not actually occur, since they are a polygynous (multiple queen) species. Different queens produce genetically different offspring, offering options for mating. Argentine ants avoid mating with siblings. Additionally, since males sometimes take flight, they can go into other foreign colonies, or remain in the original nest.

• Mating System
• polygynous polygynous
• eusocial eusocial

Argentine ants are polygynous and have multiple queens in each nest. After mating, queens remain in the nest and do not lay eggs until the following spring. However, before they lay eggs, 90% of queens are executed by workers before the reproductive season. The executions take place on foraging trails at night, where workers attack the queens like they attack prey. Workers grab the queens' legs while others attack the body, severing the gaster from the thorax. The pieces either remain on the ground, or workers carry them as they would prey. The reasons for the execution are unclear; though it likely frees up food for the brood and may play a role in differentiation of sexual offspring, as the presence of the queens and their pheromones have an effect.

Queens that have not been executed lay their first batch of eggs in the spring and continue laying throughout the summer. Queens store sperm from their first mating for the rest of their lives and typically have more sperm stored in their spermathecae than they could ever use during brood production. They can lay up to 50 or 60 eggs per day, with an average of about 20 to 30 eggs. The rate of oviposition is affected by temperature, 28 degrees Celsius is optimal. The oviposition rate is also affected by the number of queens present in the colony. A colony can have hundreds of queens. The more queens present, the lower the oviposition rate for each queen. With more queens, worker care per queen likely decreases. Less food is brought to each queen, decreasing their fitness and oviposition rate. Since queens secrete pheromones that attract workers, more queens mean more pheromones, which become muddled and less distinct, attracting fewer workers to any one specific queen.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
  • internal internal
• oviparous oviparous
• sperm-storing sperm-storing
• delayed fertilization delayed fertilization

Argentine ants provide significant brood care to the queens' offspring. Queens themselves provide provisioning in the eggs, but otherwise do not participate in brood care. Workers carry off the eggs as soon as they are laid. In laboratory colonies, workers took constant care of the eggs, moving them continuously throughout the day, perhaps to regulate humidity. Eggs are sometimes kept with larvae and pupae and sometimes separated. Eggs that are not tended by workers do not hatch, so their care is clearly important. Larvae are constantly fed food via trophallaxis by workers; the workers regurgitate food and transfer it from mouth to mouth. Workers also groom larvae and transport them. If the nest is in danger, workers pick up all brood stages and move them to safer locations. Workers help male pupae remove pupal skin when molting into adulthood, they help other pupae molt by straightening legs and antennae. Brood care extends slightly after reaching adulthood. In the 48 to 72 hours before their exoskeleton hardens, in the callow stage, the newly molted ants are unstable and wobbly. Workers still aid them if necessary, or if the nest is in danger, workers even pick up the callow ants and move them. After their exoskeleton hardens, ants join the colony and brood care stops. Workers also play a part in determining the adult role of the larvae. Workers underfeed female larvae through most of the year, which causes them to develop into workers as adults. In the spring, workers feed female larvae more, causing them to develop into queens. This change in feed is triggered by a pheromone produced by the queens.

• Parental Investment
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • female
• pre-independence
  • provisioning
    • female
  • protecting
    • female

Lifespan/Longevity

Males typically live a few days to a month or two after reaching adulthood, and usually die shortly after mating. Those that participate in a nuptial flight tend to live longer. Most queens are executed in the spring at the age of 10 months. Queens that aren't executed can live for over a year, likely several years. Workers live about 10 to 12 months.

Behavior

The behavior of Argentine ants contributes to their success as an invasive species. These ants find food sources much faster than many native species; in experiments, they find food in mazes very quickly. They minimize foraging time by establishing the shortest path to their food. This allows them to deplete food sources before native ant species find them. Argentine ants are also very aggressive towards ants and other insects that are not members of their colony, and they will defend their territory. They are also aggressive predators, groups of ants attack larger prey; a group of ants hold the prey's legs, while another group attacks the prey's body. Unlike many ant species, workers of this species have no castes or divisions of labor. All workers contribute in foraging, brood care, and other tasks. Foraging occurs on trails, typically during the day, mostly in the morning and continuing throughout the afternoon. They also perform some nighttime activities, such as the queen executions that occur in the spring. New nests are formed by budding, where one or several females leave their home nest with a group of workers and establish a new nest. Argentine ants are semi-nomadic, they move nests to more suitable areas if it is necessary, such as during floods, dry soil, or other disturbances. They may also relocate nests seasonally, as temperatures fluctuate. While they are typically found in Mediterranean climates, colonies can survive in areas with colder winters by nesting in the top few inches of soil or in piles of decaying matter. During cold temperatures, workers are sluggish, foraging stops, development times for eggs and larvae are significantly longer, and the nests is effectively hibernating.

Argentine ants live in colonies. In their native range of South America, these ants form colonies that extend about a meter, to supercolonies that extend for hundreds of meters. In their introduced range, they form gigantic supercolonies of many nests over an area of 1,000 to 4,000 km. There are no behavioral boundaries between ants from all these nests; ants from foreign nests show no aggression towards other ants of their species. Ants in these supercolonies are all genetically similar. Cooperation between ants over such a large region is one reason why Argentine ants are such a successful invasive species. Researchers have recently discovered that Argentine ants actually form a global supercolony across Europe, North America, Australia, and Japan. Argentine ants across these colonies share similar genetics, as well as similar hydrocarbon profiles on their cuticles. This supercolony likely came about due to transportation by humans.

• Key Behaviors
• terricolous
• diurnal diurnal
• motile motile
• hibernation hibernation
• territorial territorial
• colonial colonial

Home Range

Argentine ants form large colonies, with ants freely moving from nest to nest with no aggression or risk. Their home range is limited only to how far they can travel and the location of their nests, ants likely move between nests separated by several meters, though colonies can extend for thousands of meters.

Communication and Perception

Since the ability to form giant supercolonies is extremely important for the proliferation of Argentine ants, recognizing other colony members is a necessity. Nest mates identify each other by a shared colony odor on the cuticle of their exoskeleton. This odor is typically made up of hydrocarbons. By identifying nest mates, ants know when to attack and show aggression. Researchers have recently discovered that the hydrocarbon signature of ants in the introduced range is very similar between several continents, indicating a global supercolony. When Argentine ants are brought together from different continents, they do not show aggression towards each other and identify each other as nest mates. Chemicals on the cuticle also signal when an ant has died. The disappearance of certain chemicals after death alerts other ants in the nest, who collect the dead ants and move them to a waste pile. Living ants can detect a dead ant in less than an hour after death.

Touch is used to communicate between ants. Workers often groom each other, keeping the body, mandibles, and antennae clean of debris and foreign substances. Touch is also important in sensing the environment, as Argentine ants often do not notice objects unless their antennae or other body part comes into contact. This also suggests that their sight is not particularly strong, though they can detect light. Pheromones are also essential for communication. When foraging for food, Argentine ants lay down pheromones to create trails that other ants follow. Since pheromones evaporate relatively quickly, foraging ants constantly make u-turns to reinforce trail pheromones. By creating such a strong trail, Argentine ants are able to quickly recruit large numbers when a food source is found. Mass recruitment has allowed Argentine ants to beat native ants to food sources and deplete them, or overwhelm native ants that have already found food sources. This is one of the reasons why Argentine ants have been displacing so many native species. Queens produce pheromones to attract workers to provide care and bring food. Another pheromone also emitted by queens determines gyne brood production. This pheromone causes workers to overfeed or underfeed larvae. When there are many queens, workers underfeed female larvae to produce other workers. After queens are exterminated in the spring, there is less pheromone present, and workers increase the feedings, causing the sexual brood to develop.

• Communication Channels
• visual visual
• tactile tactile
• chemical chemical

• Other Communication Modes
• pheromones pheromones

• Perception Channels
• visual visual
• tactile tactile
• chemical chemical

Food Habits

Argentine ants are omnivorous. These ants prey on many different insect species. They also eat nectar from flowers and extra floral nectaries, as well as bird's eggs and dead arthropods and other carrion. A major component of their diet is honeydew farmed from aphids and scale insects . A colonies diet can change over time. Newly established colonies tend to eat protein-rich insect prey, while long-established super colonies primarily eat carbohydrate-rich honeydew. This may be because it can take time to establish long-term mutualisms with insects that can provide significant amounts of honeydew. Inside households, Argentine ants also eat any available human food, particularly sweets. Laboratory colonies show some evidence of cannibalism, feeding on their eggs and larvae.

• Primary Diet
• omnivore omnivore

• Animal Foods
• eggs
• carrion carrion
• insects
• terrestrial non-insect arthropods

• Plant Foods
• nectar

Predation

Argentine ants are highly aggressive towards other ant species and potential predators. They also use chemicals to defend themselves. They are preyed on by many spider species, including Zodarion cesari in the Mediterranean. Larval antlions of genus Myrmeleon are also known predators. Antlions catch ants that fall into their pitfall traps. Other larger insects, such as cockroaches , also feed on these ants. Larger animals, such as amphibians and reptiles, including Japanese tree frogs, Hyla japonica , as well as several bird species, including northern flickers and house sparrows also prey on Argentine ants.

Ecosystem Roles

As one of the most invasive ant species in the world, Argentine ants have an extensive impact on the ecosystems that they invade. As their range expands into new regions, Argentine ants are continually displacing native ant species and other arthropod populations. Argentine ants out-compete native species because they find food sources faster, forage longer, quickly recruit larger numbers to food sources, and function in a large range of habitats. Their ability to form supercolonies also allows cooperation on a large scale. In displacing native ant species, Argentine ants disrupt many ant-plant seed dispersal mutualisms, and do not appear to disperse seeds themselves. Argentine ants also displace pollinators, causing difficulties for native plants. By causing changes in the native arthropod communities, Argentine ants also have indirect effects on other parts of the community. Eliminating native arthropod prey may cause a decrease in bird populations and nesting habits, and may even pose a potential threat to baby birds, as large recruitment numbers could easily overwhelm a newly hatched bird. Displacing native species also negatively affects reptile, amphibian, and mammal species. This can be seen in the decreasing population size of coastal horned lizards in California, likely due to Argentine ants out-competing native ant species. Another invasive ant species, Asian needle ants are actually displacing Argentine ants from their invasive range in the eastern United States.

Argentine ants form mutualistic relationships with many honeydew-producing insects, such as aphids and coccids . The ants tend the insects and eat the honeydew they produce; in exchange they protect these insect populations from predators and parasitoids. Since honeydew is an important component of their diet, it is incredibly important that Argentine ants form these relationships with insects native to the regions they have invaded. One study found 48 species of scale insects were tended by Argentine ants in one area. By tending and protecting honeydew producers, these ants allow pest populations to flourish, decreasing the fitness of the plants on which the pests live. These ants have mutualisms with scale insects, including terrapin scales , Mediterranean black scales , California red scales , and Virginia pine scales , many species of aphids including melon aphids and oleander aphids , and mealybugs including obscure mealybugs , grape mealybugs , vine mealybugs , citrus mealybugs , and citrophilus mealybugs . Argentine ants also farm honeydew produced by gall wasp larvae. Phorid flies are parasitoids that lay their eggs on or inside Argentine ants. The larvae eat the ants' tissues, eventually killing them. Parasitic Wolbachia bacteria are common in native populations of Argentine ants, though interestingly, infections are significantly less common in introduced populations.

Economic Importance for Humans: Positive

There are no known positive effects of Argentine ants on humans.

Economic Importance for Humans: Negative

Argentine ants are one of the most invasive ant species in the world, having been distributed worldwide by human activities and travel. They significantly impact crops, human households, and native species in the regions they invade. The invasion of Argentine ants has resulted in a loss of biodiversity, as they consistently out-compete native ant species, causing negative effects on many other animal populations. While not directly damaging crops, their ability to form strong mutualistic relationships with many species of aphids and other honeydew producing insects allow these crop pests to flourish, causing greater damage to crop yields. Argentine ants also cause infrastructure damage when they invade buildings. In addition to being a nuisance, in hospital settings these ants can transfer pathogens such as Escherichia coli , Enterococcus , Streptococcus , and Staphylococcus . Researchers have searched for ways to manage and eradicate ant infestations. Due to their large numbers and supercolony structure, it is very difficult to completely remove these ants from any one area. If one nest is removed, ants from other nearby nests will likely re-colonize the area. Significant time has been invested in researching the effectiveness of pesticides and baits that can be brought back and distributed throughout the entire colony. Other researchers have found that removing or re-locating water sources can help keep ants out of buildings and homes. Argentine ants are limited by cold temperatures, but due to global climate change and warming temperatures, their range could expand even further.

• Negative Impacts
• injures humans
  • carries human disease
• household pest

Conservation Status

As an important invasive species; Argentine ants have no special conservation status. Instead, they are considered one of the 100 most invasive alien species in the world according to the Invasive Species Specialist Group (ISSG).

Other Comments

Argentine ants ( Linepithema humile ) were previously known as Iridomyrmex humilis . A 1913 government publication concerning this invasive ant species reported instances of human infants covered in swarming ants, even causing several infant deaths, but these accounts were not verified and were likely sensationalized, though the ability of Argentine ants to recruit large numbers is well documented. There is a massive amount of literature and research available concerning their impact on the ecosystems they invade, the mutualisms they establish, their supercolony structure, the damage they can do to human populations, and ways to halt their expansion and curb any further ecosystem disturbances.

Additional Links

Encyclopedia of Life

BioKIDS Critter Catalog

Contributors

Angela Miner (author), Animal Diversity Web Staff, Leila Siciliano Martina (editor), Texas State University.

References

Abril, S., J. Oliveras, C. Gomez. 2008. Effect of temperature on the oviposition rate of Argentine ant queens ( Linepithema humile Mayr) under monogynous and polygynous experimental conditions. Journal of Insect Physiology , 54/1: 265-272.

Aron, S., L. Keller, L. Passera. 2001. Role of resource availability on sex, caste and reproductive allocation ratios in the Argentine ant Linepithema humile . Journal of Animal Ecology , 70/5: 831-839.

Brightwell, R., P. Labadie, J. Silverman. 2010. Northward Expansion of the Invasive Linepithema humile ( Hymenoptera : Formicidae ) in the Eastern United States is Constrained by Winter Soil Temperatures. Environmental Entomology , 39/5: 1659-1665.

Brightwell, R., J. Silverman. 2010. Invasive Argentine ants reduce fitness of red maple via a mutualism with an endemic coccid. Biological Invasion , 12/7: 2051-2057.

Bristow, C. 1991. Are ant-aphid associations a tritrophic interaction - oleander aphids and Argentine ants. Oecologia , 87/4: 514-521.

Buczkowski, G., G. Bennett. 2008. Aggressive interactions between the introduced Argentine ant, Linepithema humile and the native odorous house ant, Tapinoma sessile . Biological Invasions , 10/7: 1001-1011.

Choe, D., J. Millar, M. Rust. 2009. Chemical signals associated with life inhibit necrophoresis in Argentine ants. Proceedings of the National Academy of Sciences of the United States of America , 106/20: 8251-8255.

Enzmann, B., K. Kapheim, T. Wang, P. Nonacs. 2012. Giving them what they want: manipulating Argentine ant activity patterns with water. Journal of Applied Entomology , 136/8: 588-595.

Fitzgerald, K., D. Gordon. 2012. Effects of Vegetation Cover, Presence of a Native Ant Species, and Human Disturbance on Colonization by Argentine Ants. Conservation Biology , 26/3: 525-538.

Glenn, S., D. Holway. 2008. Consumption of introduced prey by native predators: Argentine ants and pit-building ant lions. Biological Invasions , 10: 273-280.

Inoue, M., E. Sunamura, E. Suhr, F. Ito, S. Tatsuki, K. Goka. 2013. Recent range expansion of the Argentine ant in Japan. Diversity and Distributions , 19/1: 29-37.

Inouye, B., A. Agrawal. 2004. Ant mutualists alter the composition and attack rate of the parasitoid community for the gall wasp Disholcaspis eldoradensis ( Cynipidae ). Ecological Entomology , 29/6: 692-696.

Ito, F., M. Okaue, T. Ichikawa. 2009. A note on prey composition of the Japanese treefrog, Hyla japonica , in an area invaded by Argentine ants, Linepithema humile , in Hiroshima Prefecture, western Japan ( Hymenoptera : Formicidae ). Myrmecological News , 12: 35-39.

Keller, L., L. Passera, J. Suzzoni. 1989. Queen execution in the Argentine Ant, Iridomyrmex humilis . Physiological Entomology , 14/2: 157-163.

Keller, L., L. Passera. 1992. Mating System, Optimal Number of Matings, and Sperm Transfer in the Argentine Ant Iridomyrmex humilis . Behavioral Ecology and Sociobiology , 31/5: 359-366.

Lach, L. 2013. A comparison of floral resource exploitation by native and invasive Argentine ants. Arthropod-Plant Interactions , 7/2: 177-190.

Libbrecht, R., T. Schwander, L. Keller. 2011. Genetic components to caste allocation in a multiple-queen ant species. Evolution , 65/10: 2907-2915.

Lowe, S., M. Browne, S. Boudjelas. 2000. "100 of the World's Worst Invasive Alien Species" (On-line pdf). IUCN/SSC Invasive Species Specialist Group (ISSG). Accessed August 31, 2013 at http://www.issg.org/pdf/publications/worst_100/english_100_worst.pdf .

Markin, G. 1970. Seasonal life cycle of Argentine ant, Iridomyrmex humilis ( Hymenoptera - Formicidae ), in southern California. Annals of the Entomological Society of America , 63/5: 1238-1242.

McGrannachan, C., P. Lester. 2013. Temperature and starvation effects on food exploitation by Argentine ants and native ants in New Zealand. Journal of Applied Entomology , 137/7: 550-559.

Mgocheki, N., P. Addison. 2009. Interference of ants (Hymenoptera: Formicidae) with biological control of the vine mealybug Planococcus ficus (Signoret) ( Hemiptera : Pseudococcidae ). Biological Control , 49/2: 180-185.

Monzo, C., M. Juan-Blasco, S. Pekar, O. Molla, P. Castanera, A. Urbaneja. 2013. Pre-adaptive shift of a native predator ( Araneae , Zodariidae ) to an abundant invasive ant species ( Hymenoptera , Formicidae ). Biological Invasions , 15/1: 91-96.

Newell, W., T. Barber. 1913. The Argentine Ant . Washington D.C.: U.S. Department of Agriculture - Bureau of Entomology.

Orr, M., S. Seike. 1998. Parasitoids deter foraging by Argentine ants ( Linepithema humile ) in their native habitat in Brazil. Oecologia , 117/3: 420-425.

Passera, L., S. Aron, D. Bach. 1995. Elimination of sexual brood in the Argentine ant Linepithema humile - queen effect and brood recognition. Entomologia Experimentalis et Applicata , 75/3: 203-212.

Passera, L., S. Aron. 1996. Early Sex Discrimination and Male Brood Elimination by Workers of the Argentine Ant. Proceedings of the Royal Society B-Biological Sciences , 263: 1041-1046.

Passera, L., L. Keller. 1994. Mate availability and male dispersal in the Argentine ant Linepithema humile (Mayr) ( Iridomyrmex humilis ). Animal Behaviour , 48: 361-369.

Powell, B., J. Silverman. 2010. Impact of Linepithema humile and Tapinoma sessile ( Hymenoptera : Formicidae ) on three natural enemies of Aphis gossypii ( Hemiptera : Aphididae ). Biological Control , 54/3: 285-291.

Reid, C., T. Latty, M. Beekman. 2012. Making a trail: informed Argentine ants lead colony to the best food by U-turning coupled with enhanced pheromone laying. Animal Behaviour , 84/6: 1579-1587.

Reuter, M., J. Pederson, L. Keller. 2005. Loss of Wolbachia infection during colonization in the invasive Argentine ant Linepithema humile . Heredity , 94/3: 364-369.

Rice, E., J. Silverman. 2013. Propagule Pressure and Climate Contribute to the Displacement of Linepithema humile by Pachycondyla chinensis . PLOS ONE , 8/2: e56281. Accessed August 31, 2013 at http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0056281 .

Rodriguez-Cabal, M., K. Stuble, B. Guenard, R. Dunn, N. Sanders. 2012. Disruption of ant-seed dispersal mutualisms by the invasive Asian needle ant ( Pachycondyla chinensis ). Biological Invasions , 14/3: 557-565.

Shik, J., J. Silverman. 2013. Towards a nutritional ecology of invasive establishment: aphid mutualists provide better fuel for incipient Argentine ant colonies than insect prey. Biological Invasions , 15/4: 829-836.

Suarez, A., T. Case. 2002. Bottom-up effects on persistence of a specialist predator: Ant invasions and horned lizards. Ecological Applications , 12/1: 291-298.

Suarez, A., P. Yeh, T. Case. 2005. Impacts of Argentine ants on avian nesting success. Insectes Sociaux , 52/4: 378-382.

Torres, C., M. Brandt, N. Tsutsui. 2007. The role of cuticular hydrocarbons as chemical cues for nestmate recognition in the invasive Argentine ant ( Linepithema humile ). Insectes Sociaux , 54/4: 363-373.

dos Santos, P., A. Fonseca, M. Sanches. 2009. Ants ( Hymenoptera : Formicidae ) as vectors for bacteria in two hospitals in the municipality of Divinopolis, State of Minas Gerais. Revista da Sociedade Brasileira de Medicina Tropical , 42/5: 565-569.

University of California Agriculture and Natural Resources. 2009. "Argentine ant — Linepithema humile " (On-line). UC - IPM online. Accessed September 07, 2013 at http://www.ipm.ucdavis.edu/TOOLS/ANTKEY/argentine.html .