Hymenoptera: Formicidae

Argentine Ant     Crazy Ant/ Long legged Ant    Big Headed Ant

Photo Courtesy of http://www.forest-bird.org.nz/Biosecurity/ArgentineAnt.asp

Introduction http://www.forest-bird.org.nz/Biosecurity/ArgentineAnt.asp

Why are invasive ants so successful and detramental in Hawaii?
The Hawaiian archipelago is extremely isolated. Through evolutionary history, after the arrival of a single ancestor, high levels of radiation occurred. In the case of arthropods, this evolution was often times accompanied by extreme changes in morphology, ecology, and behavior. These radiations have resulted in high endemism; over 97% of the 5,735 decribed native species of arthropods in Hawaii are endemic (Roderick and Gillespie 1998). There are no endemic or native ant species in Hawaii (Wilson and Tayler 1967). The more than forty species of ants now established on Hawaii were introduced by humans during the last hundred years (Reimer et al. 1990). The presence of ants on Hawaii is very recent in light of millions of years of evolution (Reimer 1994). As a result, the native terrestrial arthropods have not developed defenses against ants (Reimer et al. 1990) and no specialized ant predators are present in the Hawaiian archipelago (Reimer 1994). These favorable conditions enabled ants to spread rapidly resulting in devastating consequences, primarily in low elevations, for Hawaii (Reimer 1994). Of the 3,055 invasive arthropods now present on Hawaii ants are considered to be some of the most destructive (Roderick and Gillespie 1998).

What are the impact of Invasive Ants on Hawai‘i’s native habitat?

• Endemic arthropod populations have been decimated at lower elevations by ant predation (Reimer et al.   1990).
  
• Invasive ants may effect vertebrates by eliminating their invertebrate food sources. This exploitative competition may be partly responsible for the disapperance of most native birds in Hawaiian lowlands (Banko and Banko 1976 in Wetterer 1998). High densities of ants in highlands may have contributed to the exclusion of Palila (an endangered Hawaiian endemic bird).
  
• Ants disperse seeds of alien plants (Howarth 1984).
  
• Ants are seed predators of native plants (Bond and Slingsby 1984).
  
• Ants participate in synergistic relationships with other invasive species. For instance, many pestiferous ant species tend alien honeydew-producing homopterans, like aphids, mealy bugs, and treehoppers that feed on native plants and need mutualistic ants to disperse and protect them from predators (Howarth 1984).

What are the economic impacts of ants?
Ants can be pests in agriculture (Reimer 1990) and have caused hundreds of thousands of dollars of damage in certain areas of the United States (Adams 1986 in Thompson 1990). In Hawaii, the sugar industry uses drip irrigation systems. Invasive ants chew through the plastic tubing and enlarge pre-existing holes, flooding damaged areas and causing erratic irrigation of the fields. Damage is often so severe that tubing needs to be replaced, and frequently whole crops can be lost due to severe water shortages (Chang and Ota 1990). Ants also contribute to economic losses by tending honeydew producing homopterans that damage crops (Reimer 1990).

What characteristics make tramp ants successful?
Tramp ant species are the most detrimental ants in Hawaii, and are particularly devastating to endemic arthropods (Passera 1990). Tramp ants are virtually impossible to eliminate once established (Forschler and Evans 1994) and highly successful invaders, especially in areas that have been disturbed by humans (Passera 1990). Passera (1990) outlined the following characteristics that apply to tramp ants.

• Tramp ants tend to be attracted to unstable environments and move their colonies in response to weather, physical disturbance and dietary change (depletion of or finding new resources).
  
• Tramp ants are unicolonial: there is little intraspecific aggression between ants from different nests.
  
• The absence of intraspecific aggression is tied to strong interspecific aggression, when tramp ants
  come in contact with other arthropod species they usually drive them away. Tramp species will compete with and displace other tramp ants.
  
• Polygyny is a characteristic of tramp ants. Nestmate queens do not appear to be hostile toward each other, and there is no observable dominance hierarchy.
  
• Mating occurs in the nest, and colony reproduction occurs by budding, where mated queens and workers depart on foot to establish a colony a few meters away. Populations spread slowly, but very thoroughly. Long distance dispersal occurs passively (ants on drift wood)  or through human commerce.
  
• Tramps ants tend to be very small, always less then 3.5 mm in length.
  
• The queens of tramp ants have very short life spans, tramp queens rarely live longer than one year. This is not a disadvantage because tramp species produce and rear new queens almost year round at a fairly high rate.
  
• Worker sterility is very common.

What is the distribution of ants in Hawaii?

Ants are found on all 8 main islands, and each of the largest islands of the Northwest Hawaiian Islands chain. All of the introduced ant species have been collected on Oahu, probably because it is their major port of entry. Most of the species are in the warmer, dry (0- 120 cm precipitation per year) to mesic (120- 250 cm precipitation) lowlands. Part of this distribution may be tied to the high levels of human disturbance in the lowlands in the form of land clearing, fire, agriculture, and urbanization (Reimer et al 1990).

What are ant vectors?
All invasive ants reached Hawaii through human commerce, (Wilson and Tayler 1967) then lived in more disturbed agricultural and residential lowlands before spreading to the highlands. This might explain why invasive ants are far more established in the low lands (Wetterer et al 1998).

How are ants on the islands controlled?

• Biological control and using toxic baits and sprays are the only feasible methods of ant control in natural environments (Reimer et. al 1994) (Changand Ota 1990).
  
• Biological control today is problematic and ant eradication is virtually impossible (Patterson 1994).
  
• Ants have developed techniques to protect their colonies from pathogens, parasites and predators. Ants are impeccable house cleaners and personal groomers, they quickly recognize invaders and remove them from the colony, and they secrete in their venom chemicals that have antibiotic and anti-fungal properties. (Patterson 1994).
  
• Although in residential and agricultural settings, in Hawaii, ants have been successfully controlled with toxic bates and sprays, wide spread control has not been attempted (Reimer et. al 1994) (Changand Ota 1990).
  
• Commonly used chemical barriers and repellant tend not to affect queens and non-foraging colony members because the toxins are not brought into the nest. (Forschler and Evans 1994).
  
• Delayed action insecticide has been used more successfully in controlling populations and requires less toxicant leading to less contamination then other insecticides, yet requires that foraging ants take bate material back to the colony and feed the brood and queen (Forschler and Evans 1994).
  
• Baits and sprays can lead to environmental contamination (Forschler and Evans 1994) and care needs to be taken not to poison non-target organisms (Reimer 1994).
  

Which ants are causing the greatest damage to Hawaii?
Three of the following ants have been defined as tramp species and are probably the most detrimental invasive ants on Hawaii. All three are extremely aggressive and tend to have mutually exclusive territories (Flucker and Beardsley 1970). The big headed ant (Pheidole megacephala), the long legged ant also referred to as the crazy ant (Anoplolepis longipes) occupy primarily lowland areas. The argentine ant (Linepithema humile) is found in highland areas (Wetterer et al 1998).

Though not described in detail here, it is important to note that although it has not reached Hawaii yet, another tramp ant, the red imported fire ant (Solenopsis invicta), which invaded the United States in the1930's (Thompson 1990) and originates in South America (Porter et al. 1990) reached the California coast in 1998.. Many of Hawaii’s imports come from California, including nursery stock, making the possibility of an invasion of this species fairly high. If this ant does reach Hawaii it is very likely that it will become established, and there is a high probability it will displace the current invasive tramp ants (Loope and Reeser 2001).

         
Photo Courtesy http://www.landcareresearch.co.nz/education/stowawayskidspages/invader_fact_sheet.htmSolenopsis invicta 

Impacts of the Solenopsis invicta 

• In the continental United States Solenopsis invicta has competitively replaced other ant species as well as significantly reduced densities and species richness of other arthropods (Porter 1990).
  
• Solenopsis invicta has caused significant economic losses. By 1948 it was shown to have caused more then $500,000 worth of damage to  corn, potatoes, and cabbage farms, in Mississippi alone (Adams 1986 in Thompson 1990).
  
• Solenopsis invicta has a very powerful and painful sting that can be deadly to those who are hyper-allergic; at least 83 people have died in the USA, from being stung by Solenopsis invicta (Loope and Reeser 2001).
  
• Because Solenopsis invicta has been shown to cause significant discomfort to humans it seems like it’s invasion could be devastating because much of Hawaii's economy is based on tourism (Loope and Reeser 2001).
  
  Linepithema humile
  (Argentine Ant)

                                                                                                                                                                                                         
         Photo by Neil Reimer, Hawaii State Dept. of Agriculture                 Photo Courtesy of http://www.forest-bird.org.nz/Biosecurity/ArgentineAnt.asp

Geographic Range
Linepithema humile originated in South America (Wilson and Tayler 1967) and has invaded every continent (Passera 1990).

Vectors
In all cases of introduction the vector of Linepithema humile has been human commerce. It was introduced into France with tropical plants shipped from South America, and to South Africa with animal forage shipped from Argentina. Argentine ants were brought to Hawaii with troops in the second world war (Passera 1990) and were also commonly found in cargo coming from California in the earlier part of the 20th century (Zimmerman 1941).

Impacts

• Linepithema humile indirectly impacts vertebrate populations by eliminating important invertebrate prey species (Banko and Banko 1976 in Wetterer 1998).
  
• Linepithema humile has been found to negatively impact invertebrate species, most likely through directly feeding on immature and adult organisms and competing for rock shelter (Cole et al. 1992).
  
• Linepithema humile may significantly reduce the numbers of certain endemic pollinators of native shrubs and herbaceous plants, or cause them to go extinct (Cole et al. 1992).
  
• Through predation and interspecific competition, the Linepithema humile has taken the place of endemic beetles as keystone predators in Haleakala National Park (Cole et al. 1992).
  
• Linepithema humile will tend invasive honeydew producing insects, carrying them from plant to plant, and will protect them from parasites and predation (Zimmerman 1941).
  
• This ant causes considerable trouble in houses among other things, eating food (Zimmerman 1941).

Management
Toxic baits and sprays have helped control Linepithema humile populations (Forschler and Evans 1994) and baiting in particular has been shown to control populations on a wide scale in national parks in Hawaii (Roderick and Gillespie 1998).

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Pheidole megacephala
(Big Headed Ant)

Photo by Neil Reimer, Hawaii State Dept. of Agriculture

Description
Pheidole megacephala have a dark brown coloring, the soldiers have large heads and a smooth shiny occipital region. The waist has two nodes and the propodeum has spines. Workers are 2.2 mm long, and soldiers are 3.4-3.8 mm (Huddleson and Flucker 1968). On Hawaii this ant is found in a great variety of habitats from sea level to 4000 ft., although are are most common under 3000 ft. Pheidole megacephala is the dominant ant through out the islands (Huddleson and Flucker 1968).

Geographic Range
Pheidole megacephala originated in Africa (Wilson and Tayler 1967) and was first reported in Hawaii in 1899 (Huddleston and Fluker 1968). This ant has invaded almost of the humid tropics (Wilson and Taylor 1967).

Vectors
Pheidole megacephala is distributed through commerce (Wilson and Taylor 1967).

Impacts

• The big headed ant indirectly impacts vertebrate populations by eliminating important invertebrate prey species (Banko and Banko 1976 in Wetterer 1998).
  
• This ant actively displaces native arthropod fauna where it is introduced (Fowler and Robinsom 1988 in Fowler et al. 1990).
  
• This ant aggressively defends nectar deterring natural pollinators from pollinating native plants (Howarth 84).
  
• This ant care takes mealy bugs that transmit wilt in Hawaiian and Costa Rican Pineapples. Were Pheidole megacephala not present, mealy bugs and wilt would not be a problem (Glancey et al. 1990).
  
• Pheidole megacephala is a common house hold pest (Huddleson and Flucker 1968), and often damages structures like electrical cables (Fowler 1988).

Management
Toxic baits and toxic barriers have been shown to control Pheidole megacephala populations in Hawaii (Chang and Ota 1990).

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Anoplolepis longipes
(Crazy or Long legged ant)

Photo by Neil Reimer, Hawaii State Dept. of Agriculture

Description
Anoplolepis longipes is monomorphic and yellow to reddish in color with a long slender body, long antennae and almost no standing hairs on the dorsum of the thorax. The abdomen can be darker then the head and thorax. Anoplolepis longipes moves extremely quickly (Huddleston and Flucker 1968). This ant is abundant in dry areas,(Huddleston and Flucker 1968) and can also be found at low elevations in wet forest on East Maui (Hardy 1979 in Gillespieand Reimer 1993).

Geographic Range
Anoplolepis longipes originated in South-East Asia (Haines and Haines 1978).

Vectors
This ant was distributed through commerce (Haines and Haines 1978) and was first collected on Hawaii in 1952 (Huddleston and Flucker 1968).

Impacts

• Anoplolepis longipes can be beneficial because of its competitive relationship with other pests like cockroaches, centipedes and possibly rats (Haines and  Haines 1978).
  
• Anoplolepis longipes has been shown to competitively exclude native spiders (Tetragnatha) from both native and disturbed habitats in Hawaii (Gillespie and  Reimer 1993).
  
• This ant tends green scale (Coccus viridis), a honey dew producing homoteran, which when tended occurs in high densities resulting in the growth of sooty moulds on coffee trees. Sooty mould will greatly reduce the yield and potentially kill the tree (Reimer 1990).
  
• This ant invades homes and is a serious pest to both humans and livestock (Hains and Hains 1975).

Management
Toxic bait and poison spray are currently used to control populations of Anoplolepis longipes and have been shown to reduce their numbers yet have not eradicate established populations. These meathods are particularly effective when controlling Anoplolepis longipes as a domestic nuisance and have have prevented establishment in Praslin (an island in the Saychilles) after a prompt report of a new infestation (Haines and Haines 1975).

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Links

Hawaii Ant Group (HAG)
This informative site covers a broad range of topics amoung others describing invasive ants, potential invasives, how to identify invasive ants and the current research being conduced in Hawaii.
http://hbs.bishopmuseum.org/ants/

Literature Cited

Adams, C.T. 1986. Agricultural and medical impact of the imported fire ants. In C.S. Lofgren and R.K. Vander Meer (eds.), Fire Ants andLeaf-cutting Ants Biology and Management. Westview Press, Boulder.

Banko, W.E. and P.C. Banko. 1976. Role of food depletion by foreign organisms in historical decline of Hawaiian forest birds. Pages 29-43 in Proceedings of 1st conference in Natural sciences, Hawai’i Volcanoes
National Park, Hawai‘i.

Bond, W and P. Slingsby. 1984. Collapse of an ant-plant mutualism: the argentine ant (Iridomyrmex humilis) and myrmecochorous proteacheae. Ecology 65(4) 1031-1037.

Chang, V. and A.K. Ota. 1990. Ant control in hawaiian drip irrigation Systems. Pages 708-715 In Vander Meer, R. K.; K. Jaffe and A Cedeno. Applied Myrmecology a World Perspective. Westview Press, Boulder CO.

Cole, F.R Et al. 1992. Effects of the argentine ant on arthropod fauna of Hawaiian high-elevation shrubland. Ecology 73(4) 1313-1322.

Forschler, B. T. And G.M. Evans. 1994. Argentine ant (Hymenoptera:formicidae) Foraging Activity Response to Selected Containerized Baits. Journal of Entomological Science 29(2) 209-214.

Fowler, H.G. and S.W. Robinsom. 1988. Eradication of the native ant fauna by the introduction of an exotic ant in Itapirica, Biaia, Brahia,Brazil, during hydroelectric dam construction. Environmental
Conservation.

Fowler H.G. et al. 1990 Major Ant Problems of South America. Pages 3-14 In, Vander Meer, R. K.; K. Jaffe and A Cedeno. Applied Myrmecology a World Perspective. Westview Press, Boulder CO.

Gillespie, R.G. and Reimer, N. 1993. The Effect of Alien Predatory Ants (Hymenoptera: Formididae) on Hawaiian Endemic Spiders (Araneae:Tetragnathidae). Pacific Science 47(1) 21-33.

Glancey, B.M. et al. 1990. Effects of IGR Fenocycarb and Sumitomo S-31183on the Queens of two Myrmicine Ant Species. In R.K. Vander Meer, K.Jaffe and A Cedeno. Applied Myrmecology a World Perspective. Westview Press, Boulder CO.

Haines, I.H. and J.B. Haines. 1978. Pest status of the crazy ant, Anoploepis longipes (Jerdon) (Hymenoptera: Formicidae), in the Seychelles. Bulletin of Entomological Research 68:627-638.

Hardy, D.E. 1979. An ecological survey of Puaaluu Stream. Part III. Report of a preliminary entomological survey of Puaaluu Stream, Maui. Univ. Hawaii Coop. Natl. Park Resour. Stud. Unit Tech. Rep 27.

Howarth, Frances G. 1985. Impacts of Alien Land Arthropods and Mollusks on Native Plants and Animals is Hawai’i. Pages. 149-179 in C.P. Stone and J. M. Scott. Hawai’i’s Terrestrial Ecosystems: Preservation and
Management.

Loope, L.L. and D.W. Reeser. 2001. Crossing boundaries at Haleakala:addressing invasive species through partnerships. In Harmon, D. 2001. Crossing Boundaries in Park Management in Parks and on Public Lands.
Hancock, Michigan: the George Wright Society.

Passera, Luke. 1990. Characteristics of Tramp Species. Pages 23-43 in D.F. Williams. Exotic Ants, Biology, Impact, and Control of Introduced Species. Westview Press, Boulder CO.

Porter, S.D. and D.A. Savignano. 1990. Invasion of Polygyne Fire Ants Decimates Native Ants and Disrupts Arthropod Community. Ecology 71(6) 2095-2106.

Reimer, N.J. 1994. Distribution and Impact of Alien Ants in Vulnerable Hawaiian Ecosystems. Pages 11-22 in D.F. Williams. Exotic Ants, Biology, Impact, and Control of Introduced Species. Westview Press, Boulder CO.

Roderick, GK and R.G. Gillespie. 1998. Alien arthropods in Hawaii. Aliens 8: 2-3.
URL http://www.cnr.berkeley.edu/evolab/Roderick&Gillespie.Aliens99.pdf (15 November 2002)

Reimer, N; J.W. Beardsley and G. Jahn. 1990. Pest ants in the Hawaiian Islands. Pages 40-50 in R.K. Vander Meer, K. Jaffe and A Cedeno. Applied Myrmecology a World Perspective. Westview Press, Boulder CO.

Tschinkel, W.R. 1993. The fire ant (Solenopsis invicta): still unvanquished. Pages 121-136 in B.N. McKnight (ed.), Biological Pollution: The Contol and Impact of Invasive Exotic Species. Indiana Academy of Science, Indianapolis, IN.

Wetterer, J.K; P.C. Banks; L.P. Laniawe; J.W. Slotterback and G.J. Brenner. 1998. Nonindigenous Ants at Hight Elevations on Mauna Kea, Hawai’i. Pacific Science 52(3): 228-236

Wilson, E.O. and R.W. Tayler. 1967. The Ants of Polynesia (Hymenoptera: Formicidae). Pacific Insects Monograph 14, Bishop Museum Press, Honolulu, Hi.

Zimmerman, E.C. 1941. Argentine Ant in Hawaii. Proceedings of the Hawaiian Entomological Society 11:108.

Designed by: Stephanie Schiro                                     Contact: schirst@earlham.edu
Last revised: 8 December 2002