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Linepithema humile

By Angela Miner

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. (Brightwell and Silverman, 2010; Abril, et al., 2008; Aron, et al., 2001; Brightwell and Silverman, 2010; Brightwell, et al., 2010; Inoue, et al., 2013; Lach, 2013; McGrannachan and Lester, 2013)

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. (Enzmann, et al., 2012; Brightwell and Silverman, 2010; Enzmann, et al., 2012; Fitzgerald and Gordon, 2012; Keller, et al., 1989; McGrannachan and Lester, 2013; Rice and Silverman, 2013; "Argentine ant — Linepithema humile", 2009)

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. (Markin, 1970; Newell and Barber, 1913; Passera and Aron, 1996; "Argentine ant — Linepithema humile", 2009)

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. (Markin, 1970; Newell and Barber, 1913; Passera and Aron, 1996; "Argentine ant — Linepithema humile", 2009)

  • Sexual Dimorphism
  • female larger
  • Average mass
    workers: 0.0043 g, males: 0.001 g, queens: 0.0036 g
    oz
  • Average length
    workers and males: 0.3 cm, queens: 4.5 to 5.0 cm
    in

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. (Aron, et al., 2001; Keller, et al., 1989; Libbrecht, et al., 2011; Newell and Barber, 1913)

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. (Aron, et al., 2001; Keller and Passera, 1992; Libbrecht, et al., 2011; Passera and Aron, 1996; Passera and Keller, 1994)

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. (Abril, et al., 2008; Keller and Passera, 1992; Keller, et al., 1989; Markin, 1970; Newell and Barber, 1913)

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. (Abril, et al., 2008; Keller and Passera, 1992; Keller, et al., 1989; Markin, 1970; Newell and Barber, 1913)

  • Breeding interval
    Argentine ants may mate several times, but usually only transfer sperm once.
  • Breeding season
    Mating takes place in the late spring and early summer.
  • Average time to independence
    74 days

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. (Libbrecht, et al., 2011; Newell and Barber, 1913; Passera, et al., 1995)

  • 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. (Keller, et al., 1989; Newell and Barber, 1913; Passera and Keller, 1994)

  • Range lifespan
    Status: wild
    1+ (high) years
  • Typical lifespan
    Status: wild
    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. (Brightwell, et al., 2010; Enzmann, et al., 2012; Keller and Passera, 1992; Markin, 1970; McGrannachan and Lester, 2013; Newell and Barber, 1913; Torres, et al., 2007)

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. (Inoue, et al., 2013; Torres, et al., 2007)

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. (Passera and Keller, 1994)

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. (Abril, et al., 2008; Choe, et al., 2009; Inoue, et al., 2013; Newell and Barber, 1913; Passera, et al., 1995; Reid, et al., 2012; Torres, et al., 2007)

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. (Abril, et al., 2008; Choe, et al., 2009; Inoue, et al., 2013; Newell and Barber, 1913; Passera, et al., 1995; Reid, et al., 2012; Torres, et al., 2007)

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. (Brightwell and Silverman, 2010; Lach, 2013; Newell and Barber, 1913; Shik and Silverman, 2013)

  • Animal Foods
  • eggs
  • 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. (Buczkowski and Bennett, 2008; Glenn and Holway, 2008; Ito, et al., 2009; Monzo, et al., 2013; Newell and Barber, 1913; Torres, et al., 2007)

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. (Abril, et al., 2008; Brightwell and Silverman, 2010; Buczkowski and Bennett, 2008; Inoue, et al., 2013; Lach, 2013; McGrannachan and Lester, 2013; Rice and Silverman, 2013; Rodriguez-Cabal, et al., 2012; Suarez and Case, 2002; Suarez, et al., 2005)

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. (Brightwell and Silverman, 2010; Brightwell, et al., 2010; Bristow, 1991; Inouye and Agrawal, 2004; Markin, 1970; Mgocheki and Addison, 2009; Newell and Barber, 1913; Orr and Seike, 1998; Powell and Silverman, 2010; Reuter, et al., 2005)

Mutualist Species
Commensal/Parasitic Species

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. (Abril, et al., 2008; Brightwell, et al., 2010; Enzmann, et al., 2012; Lowe, et al., 2000; dos Santos, et al., 2009)

  • 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). (Lowe, et al., 2000)

Other Comments

Argentine ants (Linepithema humile) were previously known as Linepithema humile. 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. (Newell and Barber, 1913; Passera and Keller, 1994)

Contributors

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

Glossary

Australian

Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.

World Map

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

agricultural

living in landscapes dominated by human agriculture.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carrion

flesh of dead animals.

chemical

uses smells or other chemicals to communicate

colonial

used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.

delayed fertilization

a substantial delay (longer than the minimum time required for sperm to travel to the egg) takes place between copulation and fertilization, used to describe female sperm storage.

diurnal
  1. active during the day, 2. lasting for one day.
ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

eusocial

the condition in which individuals in a group display each of the following three traits: cooperative care of young; some individuals in the group give up reproduction and specialize in care of young; overlap of at least two generations of life stages capable of contributing to colony labor

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

hibernation

the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.

internal fertilization

fertilization takes place within the female's body

introduced

referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oceanic islands

islands that are not part of continental shelf areas, they are not, and have never been, connected to a continental land mass, most typically these are volcanic islands.

omnivore

an animal that mainly eats all kinds of things, including plants and animals

oriental

found in the oriental region of the world. In other words, India and southeast Asia.

World Map

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

pheromones

chemicals released into air or water that are detected by and responded to by other animals of the same species

polygynous

having more than one female as a mate at one time

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

sperm-storing

mature spermatozoa are stored by females following copulation. Male sperm storage also occurs, as sperm are retained in the male epididymes (in mammals) for a period that can, in some cases, extend over several weeks or more, but here we use the term to refer only to sperm storage by females.

suburban

living in residential areas on the outskirts of large cities or towns.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

urban

living in cities and large towns, landscapes dominated by human structures and activity.

visual

uses sight to communicate

References

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.

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.

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