Texas leafcutter ant (Atta texana)
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Taxonomic history
Myrmi ca (Atta) texan a Buckley, 1860a PDF: 233 (w.q.m.) U.S.A. AntCat AntWiki
Taxon omi c h i story
Wheeler & Wheeler, 1974d PDF: 79 (l.).
Combination in Atta: Roger, 1863b PDF: 35; in Atta (Archeatta): Gonçalves, 1942 PDF: 343.
Junior synonym of Atta fervens: Forel, 1885a PDF: 362.
Revived from synonymy: Wheeler, 1907d PDF: 700.
Subspecies of Atta insularis: Emery, 1913bb: 259; Emery, 1924f PDF: 354; of Atta fervens: Borgmeier,
1939 PDF: 423.
Revived status as species: Gonçalves, 1942 PDF: 335.
See also: Borgmeier, 1959b: 356; Smith, 1979: 1413; Petralia & Vinson, 1980 PDF: 386.
Distribution 1,2
Fungus growing ants are found only in the new world. Atta texana is the northernmost species in the
genus Atta and is found in portions of Louisiana and Texas. In Louisiana it is mainly found west of the
Mississippi, primarily in the central portion of the state. In Texas this species is found in central and
eastern portions of the state south to the lower Rio Grande Valley. In the Rio Grande Valley these ants
are found inland and away from the mouth of the Rio Grande. This species has also been reported in
Northeastern Mexico.
Presence of Atta texana in Louisiana may stem from human activity. Ants in the genus Atta prefer
second growth forest and man-modified habitat. The clearing of the old growth pine forests in eastern
Texas may have facilitated the spread of the species in previously non-colonized areas in western and
central Louisiana.
Bi ogeograp h i c R egi on s: nearctic (Native )
Morphology 1,2
Morphologically, it is difficult to distinguish the closely related ants in the genus Atta. Differences exist
in the male reproductive organs, but the species can easily be differentiated by the odor emitted from
their crushed heads as the contents of their poison glands are liberated. Atta texana workers, queens,
and males release the smell of mint. Nevertheless, identification in the field should not be difficult for
the range of Atta texana is not known to overlap with that of other species in the genus Atta. The range
of Atta mexicana is located further south and west.
Adults are rust to dark brown and larvae are cream colored. The size of the ants varies greatly
depending on the caste and on the maturity of the colony. The size of the worker ants increase as the
colony grows and the sources of fungus within it increase. Workers range between 3 and 12 mm. The
soldiers are the largest workers, the foraging workers are medium in size, and the specialist workers are
the smallest ants found in the ant colony. The queen can be as large as 18 mm while the larvae usually
range between 6 to 13 mm long.
The shape of the ants varies depending on caste. Antennae of Atta texana have 11 segments and the
terminal club is not well defined. Workers have 3 pairs of prominent spines on the back of the thorax
and 1 pair of spines on back of head. Male reproductives have a smaller head than females.
Reproductive males and females have long dark wings and are several times larger than nonreproductive workers.
R an ge l en gth : 3 to 18 mm.
Oth er Ph ysi cal Featu res: ectothermic ; bilateral symmetry ; polymorphic
Sexu al Di morp h i sm: female larger; sexes shaped differently
Habitat 1,2
Atta texana colonizes roadsides, open fields, forests, and brushland. Deep sandy or loamy soils are best
for ant colonies. They will preferentially setup colonies where they have access to the young foliage that
they seek to harvest for the growth of their fungus. Atta texana thrives in secondary growth forest
perhaps due to the more abundant understory growth found in these forests.
Hab i tat R egi on s: temperate ; terrestrial
Terrestri al Bi omes: forest
Oth er Hab i tat Featu res: suburban ; agricultural
Trophic strategy 1,2
Texas leaf-cutting ants feed almost exclusively on a fungus that they cultivate on the clippings of
vegetation that they gather. While the workers also eat plant sap, the queen and larvae only eat the
basidiomycete fungus.
These ants will travel long distances (up to 600 ft) to attain preferred plant species. It has been
observed that they will dig tunnels under streams to get to a food source. The ants will try to harvest
leaves from different plant species in order to avoid the buildup of certain chemicals in their fungus
cultivars and keep them as healthy as possible. They use their powerful mandibles to cut sections of
leaves off of the plant. A pile of leaf fragments accumulates around the plant which other workers carry
to the nest. In only one night they are capable of defoliating an entire tree. At the nest entrance the
leaves are divided into even smaller fragments and brought to the fungus gardens. Interestingly, they
seem to prefer introduced species to native ones. They also prefer new growth to old and plants with
higher water content.
Pl an t Food s: sap or other plant fluids
Oth er Food s: fungus
Foragi n g Beh avi or: stores or caches food
Pri mary Di et: mycophage
Associations 1,2
The mutualistic relationship between the ants and the basidiomycete fungus evolved between 45 and
65 million years ago and over time has resulted in an intricate relationship between the two organisms.
When the medium-sized workers bring the leaf material back to the nest it is broken down into smaller
segments. Smaller workers lick and masticate the leaf material and break it down into pieces as small
as 1 to 2 mm. This helps remove microbes that would otherwise infect the fungus gardens and also
serves to render the substrate more suitable for fungal growth. In addition, the workers add a fecal
droplet to the masticated pulp that is believed to input important enzymes that facilitate the
breakdown of the material by the fungus. The enzymes contained in the fecal matter are derived from
the fungus consumed by the ants. This shows how strong the mutualistic relationship between the ant
and the fungus is. After this processing the ants place the pulp on top of the garden and transfer
fungus on the newly brought substrate. It takes about 6 weeks for the fungus to break down the
material after which the consumed plant matter is removed from the nest. Substrate is continually
added to the garden from the top to maintain a healthy fungus garden. The ants prune the fungus to
induce growth, and optimize growing conditions by either opening or closing surface tunnels. They can
thus regulate the temperature and humidity in the ant colony. Ants in the genus Atta clonally and
vertically propagate this fungus. The virgin queen takes a part of the fungus grown by the parent colony
and starts cultivating it into her new nest. The fungus mainly reproduces asexually and thus cultivars
transmitted from generation to generation are clones of each other.
Female phorid flies of the species Myrmosicarius texanus and Apocephalus wallerae parasitize workers
of A. texana harvesting leaves by depositing their eggs on the foragers’ heads or thoraxes using their
specialized ovipositors. The flies will be more likely to deposit their eggs on the bodies of larger workers
because the size of the host determines the extent of the fly larval growth. Unlike in other Atta species
such as Atta colombica, minim workers of Atta texana are not known to ride on leaves carried by
foraging workers to thwart off parasitizing attempts by phorid flies.
The inquiline roach Attaphila fungicola is often found associated with the fungus gardens of most Atta
texana nests. The roaches disperse by attaching their bodies to virgin queens as they take on their
mating flights. They successfully disperse to new ant colonies in this manner.
Ecosystem Imp act: soil aeration
M u tu al i st Sp eci es:
basidiomycete fungus
Commen sal /Parasi ti c Sp eci es:
phorid flies (Myrmosicarius texanus)
phorid flies (Apocephalus wallerae)
ant cockroach (Attaphila Fungicola)
Behaviour 1,2
Using their sting, workers make trails with a pheromone: methyl 4-methylpyrrole-2-carboxylate. The
pheromone is released from poison glands. Trails made by the poison glands of workers of larger size
are more detectable then those made by workers of minor size because their sacs contain more
pheromone. Mandibular glands of Atta texana contain two ketones that are both used for
communication by ants: 4-methyl-3-heptanone and 2-heptanone. High concentrations repel and alarm
the ants while low concentrations attract and alarm the ants.
Commu n i cati on Ch an n el s: tactile ; chemical
Oth er Commu n i cati on M od es: pheromones ; scent marks
Percep ti on Ch an n el s: visual ; infrared/heat ; tactile ; vibrations ; chemical
Life cycle 1,2
Atta texana goes through four developmental stages. Within the nest, the queen lays tiny eggs that
hatch as larva. The larvae are grub like, have no eyes or legs, and eat regurgitated fungus from adult
ants. After they have molted several times, the larvae spin a silky cocoon around themselves and
metamorphose. This is called the pupa stage. They emerge from their cocoon as adults, and lifespan
varies between castes.
Devel op men t - Li fe Cycl e: metamorphosis
Life expectancy 1,2
There is variation in longevity within castes. The queen lives as long as the colony, which can be over a
decade, but workers live one or two years. Under laboratory conditions, queens of species in the genus
Atta have been shown to live over 10 years. Atta cephalotes may live to 13.0 years and Atta sexdens to
15.3 years.
Typ i cal l i fesp an
Statu s: wi l d : 1 to 10+ years.
Reproduction 1,2
Atta texana are eusocial. On clear and moonless nights from April to June, winged males and females
take flight to mate. Usually this occurs after a heavy rainfall, more than a ¼ of an inch of rain, but in
areas of high rainfall this flight may take place anytime during the spring. After mating, the males die
and the mated females return to the ground, lose their wings, and begin new colonies as queens.
It is not known how many times females reproduce. There is genetic evidence that some females may
mate twice in their lifespan. However, males carry almost exactly the same amount of spermatozoa as
the queens are able to carry in their spermatheca, suggesting that they mate only once.
M ati n g System: eusocial
Typically colonies have a single fertile queen which continually produces eggs (up to two million).
Colonies may have up to 4 or 5 fertile queens. Most of the larvae develop into sterile female worker ants
but reproductives that number in the thousands are produced annually when the colony reaches a big
enough size and for as long as the fertile queen lives. In order for reproductives to leave the colony and
take flight, workers ensure that the exits are wide enough and free of debris. Reproductives develop
into winged fertile males and females in the spring. Prior to mating, the virgin queen takes a small
portion of the fungus garden from the parent colony and stores it in her infrabuccal pocket, a hollow
space and filtering device in mouths of ants. After mating the queen establishes a new colony with the
fungus she conserved from the parent colony. The queens may congregate with other queens to form
new colonies.
Breed i n g i n terval : Reproductive Texas leaf-cutting ants will breed once in their lifetimes.
Breed i n g season : Reproductive Texas leaf-cutting ants breed from April to June.
K ey R ep rod u cti ve Featu res: gonochoric/gonochoristic/dioecious (sexes separate); parthenogenic ;
sexual ; fertilization (Internal ); oviparous ; sperm-storing ; delayed fertilization
During the early stages of the colony the queen takes care of her first brood of ants. This first brood
becomes worker ants, which can then tend the next generation of ants. Larval ants are kept in close
proximity to the fungal gardens which provide food for the developing young. As the colony grows,
small nurse ants are developed to take over the task of rearing the larvae.
Paren tal In vestmen t: female parental care ; pre-hatching/birth (Provisioning: Female, Protecting:
Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence
(Provisioning: Female, Protecting: Female)
Statistics of barcoding coverage: atta texana 3
Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 5
Species With Barcodes: 1
Conservation status 1,2
These ants are in no need of conservation as they are plentiful in numbers and considered to be a pest
by some.
US Fed eral Li st: no special status
CITES: no special status
Uses 1,2
Atta texana is considered a major pest in Texas and Louisiana. The foraging activities of the ant damage
crops and prevent the reforestation of southern yellow pines. It is estimated that Atta texana is
responsible for United States $5 million in annual agricultural losses. Atta texana is also known to
damage landscape plants and gardens. Young pine seedlings are destroyed in a matter of days but will
not be attacked once they reach a height two to three feet. The ants defoliate pine trees usually when
other green plants are scarce such as during the winter. Damage done by the leaf-cutting ants
resembles damage carried out by cutting bees and sawflies. The pest has been occasionally sited in
homes carrying food material such as cereal, but this is only a minor occurrence and problem.
N egati ve Imp acts: injures humans (bites or stings); crop pest
References
1. Chausson, A. 2011. "Atta texana" (On-line), Animal Diversity Web. Accessed April 27, 2013 at
http://animaldiversity.ummz.umich.edu/site/accounts/information/Atta_texana.html
2. © The Regents of the University of Michigan and its licensors, some rights reserved
3. © Barcode of Life Data Systems, some rights reserved