Animal Diversity Web

Ge­o­graphic Range

Eciton burchel­lii is found in the trop­i­cal re­gions of Cen­tral and South Amer­ica. (Holl­dobler and Wil­son, 1990)

• Biogeographic Regions
• neotropical
  • native

Habi­tat

Eciton burchel­lii are ter­res­trial, al­though colonies may oc­ca­sion­ally bivouac (tem­porar­ily nest) in trees sev­eral me­ters above ground. Army ants need very humid, warm cli­mates. Al­though they may ven­ture out to for­age in open or agri­cul­tural areas, they pre­fer heav­ily forested en­vi­ron­ments. (Akre, 1968; Franks, 1982; Holl­dobler and Wil­son, 1990)

• Habitat Regions
• tropical
• terrestrial

• Terrestrial Biomes
• forest
• rainforest
• scrub forest

• Other Habitat Features
• agricultural

Phys­i­cal De­scrip­tion

Eciton burchel­lii are poly­mor­phic, worker sizes range from 3mm to 12mm. They have long, pointed, fal­cate (hook-shaped) mandibles. Their long legs on an elon­gated body make them ap­pear al­most spi­der-like. On their feet are tarsal hooks, which they use to grip each other as they form bridges and bivouacs. They range from a deep golden color to a dull brown. Work­ers have sin­gle faceted, com­pound eyes, dou­ble seg­mented waists, and a well-de­vel­oped sting. (Franks, 1982)

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

• Sexual Dimorphism
• female larger
• sexes shaped differently

• Range length

  3 to 12 mm

  0.12 to 0.47 in

De­vel­op­ment

Eggs are laid by the queen and are then taken away and arranged through­out the cen­ter part of the bivouac. At the same time, the lar­vae from the pre­vi­ous cycle begin to pu­pate, spin­ning silken co­coons for them­selves. Once en­closed in their co­coons, they are placed on the outer edges of the bivouac to meta­mor­phose. After meta­mor­pho­sis is com­plete, new adults need help from other colony mem­bers to eclose (emerge from their co­coons). As they begin to move within the co­coon, work­ers no­tice the vi­bra­tions and as­sist the cal­low (new) work­ers to emerge. As cal­lows eclose, the new eggs begin to hatch into lar­vae. An ac­tive lar­val brood stim­u­lates the work­ers of the colony chemo­tac­tu­ally, en­er­giz­ing the colony to a “high pitch” dur­ing the lar­val de­vel­op­ment, and the no­madic con­di­tion is begun and main­tained. As the lar­vae of Eciton burchel­lii pass through five lar­val in­stars be­fore pu­pat­ing, nightly mi­gra­tions of the bivouac are nec­es­sary in order to pro­vide the high fat diet needed for the brood to de­velop. (Akre, 1968; Holl­dobler and Wil­son, 1990; Schneirla, 1949; Schneirla, et al., 1954)

• Development - Life Cycle
• metamorphosis

Re­pro­duc­tion

The queen is able to store sperm in order to fer­til­ize all of her eggs after mat­ing only once. It has been sug­gested that queens of this species may mate up to five times over their life­times, al­though more re­search is needed in this area. Eciton queens are un­usual in that they do not have wings. A queen will mate when a winged male is dis­cov­ered by for­ag­ing work­ers and brought back to the bivouac. A male army ant will only mate with one queen in his life­time. After a short pe­riod, usu­ally less than 48 hours, he will die. (Holl­dobler and Wil­son, 1990)

On the queens propodium and peti­ole are horns pointed be­hind her. Males have been ob­served to grasp these horns with their mandibles while mat­ing. (Got­wald, 1995)

• Mating System
• polyandrous
• eusocial

The sta­tion­ary con­di­tion oc­curs when the lar­vae begin to pu­pate and the physo­gas­tric (swollen with eggs) queen lays eggs. No­madic nights begin again when cal­low (new) work­ers emerge from the pupae and many thou­sands of eggs hatch into a new gen­er­a­tion of lar­vae. (Holl­dobler and Wil­son, 1990)

New colonies are formed when new queens emerge from their co­coons. Since army ant queens are wing­less, work­ers bond to the queen through chem­i­cal scents as they care for her while still in the par­ent colony. Even­tu­ally, the group of work­ers that has bonded with the new queen will leave the par­ent colony and begin a satelite colony with their young, new queen. For the first sev­eral days work­ers often go back and forth be­tween the satelite and par­ent colonies. After this new (vir­gin) queen has mated and the new colony be­gins to in­crease in num­bers, it be­comes its own full fledged colony, and work­ers from each colony no longer rec­og­nize each other and will fight mem­bers of the other as if they had never been re­lated. (Akre, 1968; Got­wald, 1995; Schneirla, 1947)

• Key Reproductive Features
• iteroparous
• year-round breeding
• sexual
• fertilization
  • internal
• oviparous
• sperm-storing
• delayed fertilization

• Breeding interval

  The queen lays a new cycle of eggs aproximately every three weeks.

• Breeding season

  Internally fertilized eggs are layed in three week cycles year round. Mating must take place only once (although it may happen up to five times) in the life of each queen.

Ants pro­vide for their de­vel­op­ing brood with care. Al­though the queens only job is to lay eggs, the work­ers care dili­gently for every egg, larva, and pupa. Pri­mary care­tak­ers of broods are called min­ims, and tend to be smaller sized ants. As tem­per­a­ture and hu­mid­ity change through­out the day, min­ims will move broods around within the colony so that abi­otic con­di­tions are al­ways as fa­vor­able as pos­si­ble for de­vel­op­ment within the colony. In ad­di­tion to mov­ing broods around within the bivouac, the bivouac it­self changes shape in re­sponse to chang­ing abi­otic fac­tors out­side in order to keep con­di­tions con­stant within the colony walls. (Got­wald, 1995)

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

Lifes­pan/Longevity

Work­ers live for sev­eral months while queens may live for sev­eral years. Lit­tle in­for­ma­tion is known about the exact life­times as this species is very dif­fi­cult to keep in cap­tiv­ity, and its no­madic be­hav­ior makes in­di­vid­u­als very dif­fi­cult to track over long pe­ri­ods of time. (Got­wald, 1995)

Be­hav­ior

Army ants (Do­ryli­nae) are char­ac­ter­ized by their unique no­madic be­hav­ior pat­tern and purely car­niv­o­rous diet (Schneirla 1956, Schneirla et al. 1954). Eciton burchel­lii and its close rel­a­tive, Eciton hama­tum are fully ter­res­trial (Schneirla, 1947), un­like many other army ant species even within the same genus (Schneirla et al 1954). Eciton burchel­lii are swarm raiders, for­ag­ing in a dense fan shaped swarms that can span sev­eral me­ters across, at­tached to the tem­po­rary nest (bivouac) by a sin­gle col­umn that can it­self ex­tend over 200 me­ters. Their large colony size of 100,000 to 2,000,000 adult in­di­vid­u­als (Got­wald, 1995) make their for­ag­ing swarms es­pe­cially in­tim­i­dat­ing. The most dis­tin­guish­ing fea­ture of army ant be­hav­ior is the two reg­u­larly al­ter­nat­ing phases of colony life. Dur­ing the no­madic phase there are major for­ag­ing raids each the day end­ing in a change of nest lo­ca­tion, while the sta­tion­ary colonies go out on less vig­or­ous and less fre­quent for­ag­ing raids, with the nest site re­main­ing con­stant (Schneirla 1947, and Schneirla et. al 1954). Bivouac struc­ture is com­prised of liv­ing work­ers cling­ing to­gether by spe­cial­ized tarsal hooks (Schneirla, 1956). (Got­wald, 1995; Holl­dobler and Wil­son, 1990; Schneirla, 1947; Schneirla, 1956; Schneirla, et al., 1954)

• Key Behaviors
• arboreal
• terricolous
• diurnal
• nocturnal
• motile
• nomadic
• social
• colonial

Com­mu­ni­ca­tion and Per­cep­tion

Army ants, like all ants, have a va­ri­ety of ways to com­mu­ni­cate with one an­other. Most im­por­tant are chem­i­cal sig­nals. Chem­i­cals called pheromones can be re­leased into the air to sig­nal alarm, food, or used for recog­ni­tion of a nest mate. Work­ers also use chem­i­cals to mark for­ag­ing trails by wip­ing their ab­domens on the ground as they walk. Chem­i­cals can ad­di­tion­ally be used to com­mu­ni­cate needs for as­sis­tance, food, tropho­laxis (the ex­change of oral or anal fluid), con­trol of re­pro­duc­tion within the colony, and sex­ual com­mu­ni­ca­tion. In ad­di­tion to chem­i­cal sig­nals, army ants com­mu­ni­cate with vi­bra­tions and touch. Army ants do not rely on vi­sual com­mu­ni­ca­tion as they are al­most com­pletely blind. (Holl­dobler and Wil­son, 1990)

• Communication Channels
• tactile
• acoustic
• chemical

• Other Communication Modes
• pheromones
• scent marks
• vibrations

• Perception Channels
• polarized light
• tactile
• acoustic
• vibrations
• chemical

Food Habits

Army ants work to­gether to catch, sub­due, and carry their prey back to the bivouac. They sub­due prey with pow­er­ful stings, while also pulling off legs and an­ten­nae using mandibles made for pinch­ing and grip­ping. Their sharp pointed mandibles do not have a good cut­ting edge, so any­thing too big to be car­ried back that can­not be eas­ily pulled apart is left be­hind. For­ag­ing di­rec­tion dur­ing the sta­tion­ary pe­ri­ods shifts 123 de­grees per raid, while for­ag­ing dur­ing the no­madic phase tends to be in the same di­rec­tion every­day. (Franks, 1982; Holl­dobler and Wil­son, 1990; Schneirla, 1956)

Al­though in­sect types com­pris­ing the Eciton burchel­lii diet vary slightly be­tween wet and dry sea­sons, it is con­sis­tently di­verse and high in fat. Franks (1987) found that dur­ing the wet sea­son the ma­jor­ity of food items brought back to the nest are wasp and ant broods, while cock­roaches and crick­ets pre­dom­i­nate in the dry sea­son. Schneirla (1956) ob­served sig­nif­i­cantly more vari­a­tion year round, with taran­tu­las, scor­pi­ons, bee­tles, roaches, grasshop­pers, as well as other hy­menopteran adults and broods, and other in­sects, mak­ing up their diet. He also wit­nessed snakes, lizards, and nestling birds being at­tacked, al­though there are no ac­counts of ver­te­brate prey being car­ried back to the bivouac. Other arthro­pods es­cape through ex­ci­ta­tory se­cre­tions, re­pel­lent chem­i­cals, or tonic im­mo­bil­ity. (Franks, 1982; Franks, 1982; Holl­dobler and Wil­son, 1990; Schneirla, 1956)

• Primary Diet
• carnivore
  • insectivore
  • eats non-insect arthropods

• Animal Foods
• eggs
• body fluids
• insects
• terrestrial non-insect arthropods

• Foraging Behavior
• stores or caches food

Ecosys­tem Roles

Many Eciton colonies have been ob­served to con­tain “ecitophiles”, bee­tles and other arthro­pods that rely on these ants (Schneirla 1956). Eciton burchel­lii is specif­i­cally known to have re­la­tion­ships with Eu­x­enis­ter bee­tles which live in the nest, travel with the bivouac, groom adult work­ers, and in­dis­crim­i­nately feed off booty and broods (Akre 1968). Sev­eral species of mite also call the army ant bivouac home, while thou­sands of small ver­te­brates and in­ver­te­brates alike are gob­bled up by ant birds (in­clud­ing Formi­cari­idae and Thamnophil­i­dae) while es­cap­ing the at­tack­ing ant swarm. Ant birds are birds from at least four dif­fer­ent fam­i­lies that de­pend heav­ily upon the swarm­ing army ants to dis­turb small an­i­mals that are then gob­bled up. These birds are com­monly found fol­low­ing ant for­ag­ing trails. (Akre, 1968; Got­wald, 1995; Schneirla, 1956)

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

Eciton burchel­lii can be very ben­e­fi­cial in terms of re­mov­ing agri­cul­tural and house­hold in­sect pests. (Got­wald, 1995)

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

Al­though E. burchel­lii has a painful sting and will ag­gres­sively pro­tect the bivouac and fel­low work­ers, this species does not fre­quently come into con­tact with peo­ple.

• Negative Impacts
• injures humans
  • bites or stings
  • venomous

Con­ser­va­tion Sta­tus

There is no spe­cial sta­tus for these ants.

• IUCN Red List

  No special status

• US Federal List

  No special status

• CITES

  No special status

Con­trib­u­tors

Sara Di­a­mond (au­thor), An­i­mal Di­ver­sity Web.

Ref­er­ences

Akre, D. 1968. The Be­hav­ior of Eu­x­enis­ter and Pul­vin­is­ter His­terid Bee­tles As­so­ci­ated with Army Ants. Pan­Pa­cific En­to­mol­o­gist, 44: 87-101.

Brown, T. 2004. "In­fi­nite World" (On-line). Ac­cessed Feb­ru­ary 09, 2005 at http://​www.​infiniteworld.​org/​research/​research%20background.​htm.

Franks, N. 1982. Ecol­ogy and Pop­u­la­tion Reg­u­la­tion in the Army Ant Eciton burchel­lii . Pp. 389-403 in The Ecol­ogy of a Trop­i­cal For­est. United States of Amer­ica: The Smith­son­ian In­sti­tute.

Got­wald, W. 1995. Army Ants: The Bi­ol­ogy of So­cial Pre­da­tion. Ith­ica, NY, USA: Cor­nell Uni­ver­sity Press.

Holl­dobler, B., E. Wil­son. 1990. The Ants. United States of Amer­ica: Har­vard Uni­ver­sity Press.

Schneirla, T. 1947. A Study of Army-Ant Life and Be­hav­ior Under Dry-Sea­son Con­di­tions with Spe­cial Ref­er­ence to Re­pro­duc­tive Func­tions.. Amer­i­can Mu­seum Novi­tates, 1336.

Schneirla, T. 1949. Prob­lems in the En­vi­ron­men­tal Adap­ta­tion of Some New-World Species of Do­ry­line Ants.. Anales del In­sti­tuto de Bi­olo­gia., Tomo XX, Nos. 1 & 2.

Schneirla, T. 1956. The Army Ants. The Smith­son­ian Re­port, Re­port for 1955: 379-406.

Schneirla, T., R. Brown, F. Brown. 1954. The Bivouac or Tem­po­rary Nest as an Adap­tive Fac­tor in Ver­tain Ter­res­trial Species of Army Ants. Eco­log­i­cal Mono­graphs, 24: 269-296.

Snelling, G., R. Snelling. 2002. "New World Army Ants" (On-line). Ac­cessed Feb­ru­ary 09, 2005 at http://​www.​armyants.​org.