Azteca

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Azteca
Temporal range: 19–0 Ma
Early Miocene – Recent
Azteca adrepens
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Dolichoderinae
Tribe: Leptomyrmecini
Genus: Azteca
Forel, 1878
Type species
Liometopum xanthochroum, now Azteca xanthochroa
Diversity
112 species
2 fossil species
(Species Checklist)

Azteca adrepens casent0173822 profile 1.jpg

Azteca adrepens

Azteca adrepens casent0173822 dorsal 1.jpg

Specimen Label

All known species are arboreal, nesting in living or dead wood, or external carton nests. Some species exhibit obligate associations with myrmecophytes, especially of the genus Cecropia. Feeding habits are generalized with foraging occurring both arboreally and on the ground. The species level taxonomy of this genus is in need of revision, with the exception of a few modern treatments that have carefully delineated numerous species within species groups or from specific areas. Workers tend to have few distinguishing characters. Queens are more distinctive, so much so that species are now described and identified from the queens rather than workers. Unfortunately collecting a queen can be an onerous task.....many species are very aggressive when their nests are disturbed.

Identification

Queens are typically better for identifying Azteca species than the workers. See the caste and nomenclature sections below for more information about queen/worker morphology and species delineation problems within the genus.

Longino (2007) - The taxonomic bounds of the genus have not changed since its inception (Forel 1878, Shattuck 1992). Members of the genus can be recognized by the combination of (1) a thin, somewhat flexible cuticle, (2) anterolateral margins of clypeus extending anterior to mediolateral regions (with the exception of the aurita group, as reported here), (3) mandible with 7–9 teeth, (4) at least larger workers with cordate head shape, with margin of vertex concave, (5) surface sculpture (other than on mandibles) smooth, micropunctate, microalveolate, or combinations of these, (6) the total absence of coarse surface elements such as spines, tubercles, carinae, rugae, striations, or large puncta, (7) a distinctive petiole which is strongly sloping anteriorly and has a rounded posteroventral lobe, and (8) worker caste polymorphism.

The Asian genus Philidris (former Iridomyrmex cordatus group) is highly convergent with Azteca. In contrast to Azteca, the anterolateral margins of the clypeus are posterior to the mediolateral portions, and the mandible has 10–12 teeth. Male characters (Shattuck 1992) and recent molecular evidence (P. S. Ward, pers. com.) ally Philidris with other Asian dolichoderines and confirm that the similarity is due to convergence.

Shattuck (1992) - Worker: Polymorphic, majors with ocelli; anterolateral clypeal margin with the corners expanded anterior of the mediolateral region; vertex concave; petiolar scale strongly inclined anteriorly, and with a distinct ventral node; dorsal face of propodeum longer than declivitous face; mandible with 7-9 teeth and no denticles, and with the apical tooth subequal in size to the subapical; metanotal groove forming a distinct angle between the mesonotum and propodeum. Central and South America. Queen: Propodeal angle indistinct; petiolar scale strongly inclined anteriorly and with the anterior face much shorter than the posterior face; venter of petiole with a well developed, rounded lobe; wing with one closed cubital cell. Male: Second funicular segment barrel-shaped; petiolar scale with a blunt angle or a single tooth or projection dorsally; pygostyles vestigial; mandible with 1 to 4 teeth and 0 to about 3 denticles; first gastral segment vertical (not concealing the petiole in dorsal view), and with a groove or indentation for the reception of the entire height of the petiole.

The worker caste can generally be recognized in the field by its cordate-shaped head, large foraging columns and habit of running with the gaster raised. Azteca workers are most similar to those of the Old World genus Anonychomyrma, but are separable based on the presence of ocelli in larger workers (ocelli are also present in one species of Anonychomyrma) , a smaller subapical mandibular tooth, a strongly anteriorly inclined petiolar node, and a polymorphic worker caste. Additionally, the Azteca proventriculus is distinct in having the copula excised laterally, without phragma, and only slightly broader than the bulb; the bulb being exposed in lateral view; and the presence of an occlusory tract.

Keys to Species in this Genus

Distribution

World distribution based on political regions. View/Edit Data
Azteca Distribution.png Worlddistribution legend.jpg

Species richness

Species richness by country based on regional taxon lists (countries with darker colours are more species-rich). View Data

Azteca Species Richness.png

Biology

During an Ant Course in Venezuela, Brian Fisher and Jack Longino opened a nest of these aggressive ants. Their video demonstrating the discomfort Azteca can deliver to ant collectors is well worth watching.
Longino (2007) - The dolichoderine genus Azteca is a strictly neotropical group of arboreal ants (Emery 1893, Forel 1928). They are abundant in lowland habitats from Mexico to Argentina, occurring as both generalized foragers and as specialized inhabitants of myrmecophytic plants. Azteca species exhibit a variety of nesting habits, including the construction of carton nests, the occupation of live and dead plant stems (Forel 1899, Ule 1901, Emery 1913, Davidson 1988, Ayala et al. 1996), and the formation of ant gardens. Ant gardens are arboreal ant nests which sprout epiphytes from carton nest material (Ule 1901, Wheeler 1921, Longino 1986, Davidson 1988, Corbara et al. 1999, Kaufmann & Maschwitz 2006). Striking cases of symbiosis occur between Azteca and highly specialized myrmecophytic plants, the most notable case being the relationship between Azteca and Cecropia (Müller 1876, 1880–1881, Bequaert 1922, Wheeler 1942, Benson 1985, Longino 1991a, b). Also, Azteca ants have developed complex trophic relationships with many species of coccoid Hemiptera (Wheeler 1942, Johnson et al. 2001, Davidson et al. 2003). Azteca workers are often found tending mealy bugs (Pseudococcidae) and soft scales (Coccidae). For Azteca species that nest in live stems, the interior walls of the nest are often encrusted with mealy bugs and scales. Species building carton nests and ant gardens maintain dense populations of mealybugs and scales under the carton of the main nest or under small carton “pavilions” scattered over the vegetation. Very little attention has been paid to the taxonomic diversity of Coccoidea associated with Azteca, and usually only cursory observations of their presence are made during field collections. Because of the richness of the ecological interactions among Azteca, plants, and hemipteran symbionts, Azteca species have been and will continue to be subjects in the study of adaptation and coevolution, and therefore taxonomic work on the genus is particularly important.

Correlated with sharp differences in queen morphology are distinctive nesting habits. Nesting habits show great interspecific variation and little intraspecific variation. For example, queens of Cecropia-inhabiting species colonize very young Cecropia saplings. These queens are often very abundant in the environment, colonizing saplings and apparently competing for domination of saplings (Longino 1989b). I have made extensive collections of neotropical arboreal ants by breaking live and dead branches, searching for carton nests and ant gardens, and dissecting other myrmecophytes such as Cordia, Acacia, Triplaris, Tococa, and Ocotea. The Azteca species which dominate Cecropia trees are found only in Cecropia trees. In spite of high queen density and competition for saplings, I have never encountered one of these Azteca species, either colonies or founding queens, in any plant cavity other than that of a Cecropia. Thus, when only workers are available, biological data on nest site can be of critical diagnostic importance.

Castes

Longino (2007) - Wheeler and Bequaert (1929) stated “Apparently the females [i.e., queens] furnish more reliable characters for identification than the workers in the genus Azteca.” An analogy can be drawn between the taxonomy of Azteca and the taxonomy of many plants. Botanists typically shun sterile material because it is often more plastic within species and less differentiated between species than reproductive material. Such is the case in Azteca. Workers are polymorphic within colonies, and colonies exhibit prolonged ontogenetic changes in worker morphology (pers. obs.). In contrast, queens are much less variable morphologically and exhibit strong interspecific differences. Within a single locality, species with strongly differentiated queens may have workers that are barely distinguishable.

Morphology

Worker Morphology

 • Antennal segment count 12 • Antennal club gradual • Palp formula 6,4; 5,3; 4,3; 4,2 • Total dental count 7-9 (some +) • Spur formula 1 simple, 1 pectinate • Eyes present • Scrobes absent • Caste polymorphic • Sting absent

Nomenclature

The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.

  • AZTECA [Dolichoderinae: Leptomyrmecini]
    • Azteca Forel, 1878: 384. Type-species: Liometopum xanthochroum, by monotypy.
    • [Type-species not Tapinoma instabilis, unjustified subsequent designation (based on inaccurate synonymy) by Wheeler, W.M. 1911f: 159. Type-species not Azteca muelleri, unjustified subsequent designation by Emery, 1913a: 31; repeated in Wheeler, W.M. 1913a: 78.]
  • [Aztecum Bertkau, 1879: 13, incorrect subsequent spelling.]

Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.

Longino (2007) - The relative clarity of the generic status of Azteca is not mirrored in species-level taxonomy. Several factors contribute to taxonomic confusion in Azteca, some historical, some biological. The only revision of the genus Azteca is that of Emery (1893). Over 140 species-group names were subsequently published by Forel, Wheeler, and others, with no attempts at revision. Many species were described from workers only, with no biological data. Since it is often particularly difficult to separate Azteca species with workers only (Longino 1991a, b, 1996), many named Azteca species are difficult to circumscribe.

Because of the unreliability of worker morphology, many names in Azteca may remain in nomenclatural limbo indefinitely. Identities of species based solely on a type series of workers, with no data on queen morphology or nesting behavior, will only be resolved by a thorough understanding of the subtle differences between workers of all the species at the type locality

Description

Shattuck (1992):

Worker

HEAD. Vertex weakly to strongly concave. Compound eyes present, approximately round; relatively anterior on head. Ocelli present (in majors). Antennae 12 segmented. Scape short, at most surpassing the vertex by less than one- third its length. Anterolateral clypeal margin even with the mediolateral region and commonly with the corners expanded slightly anterior of the mediolateral region. Anteromedial clypeal margin entire, without a central notch or concavity of any type. Anterior clypeal setae 6-14; short, less than twice the maximum scape diameter; straight. Posterior clypeal margin between the anterior and posterior surfaces of the antennal socket cavities. Anterior tentorial pit nearer the antennal socket than the mandibular insertion. Frontal carina present. Anterolateral hypostoma reduced to a thin sclerite. Medial hypostoma entire. Psammophore absent. MOUTHPARTS. Palp formula 6:4,5:3,4:3 or 4:2 (rarely 5:3 partly fused into 4:3). Third maxillary palp segment subequal in length to segment 4. Fifth maxillary palp segment at the apical extreme of segment 4. Mandible with 7-9 teeth and no denticles. Apical tooth subequal in length to the subapical tooth. Basal angle distinct, with a well developed tooth or angle separating the masticatory and basal margins. Basal margin varying from smooth (without teeth or denticles) to denticulate along entire surface. MESOSOMA. Posteroventral pronotum lateral, rounded or angled. Mesopleural process absent. Anteromedial mesosternum even with the lateral regions. Declivitous face of propodeum convex; dorsal face flat or convex, longer than the declivitous face. Propodeal angle indistinct to moderately distinct. Mesosomal spines and tooth absent. Erect pronotal hairs 4-20 (rarely absent); when present elongate, much longer than the maximum scape width. Dorsal pro-mesonotal junction with the pronotum and mesonotum even, or with the mesonotum above the pronotum. Metanotal groove forming a distinct angle between the mesonotum and propodeum. Metanotal spiracle dorsal and lying on the dorsal surface when viewed in lateral profile. Propodeal spiracle lateral and ventral of the propodeal dorsum (sometimes appearing dorsal because of reduction of dorsal propodeum). Hind tibial spur with well developed barbules along entire inner surface (except extreme base). PETIOLE. Scale present; ridged and with a distinct angle dorsally; strongly inclined anteriorly and with the anterior face much shorter than the posterior face. Venter with a well developed lobe. GASTER.• First tergite vertical and not concealing the petiole in dorsal view and with a groove or indentation for the reception ofthe basal portion ofthe petiole. Anteriortergosternal suture ofthe first segment extending laterally from the helcium, without or with at most a very weak dorsal arch. Fifth tergite ventral, gaster with 4 apparent tergites. Gastral compression lateral, dorsoventral, or absent (gaster circular in cross section). Fourth sternite keel-shaped posteriorly. GENERAL CHARACTERS. Worker caste polymorphic. Chromosome number unknown. Integument thin and flexible, weakly sculptured. PROVENTRICULUS. Cupola slightly broader than bulb; excised; with short pile; smooth, without sculpture; and without phragma. Bulb exposed in lateral view. Longitudinal muscle No.1 present. Occlusory tract present.

Queen

HEAD. Vertex weakly convex to weakly concave. Compound eyes relatively anterior on head. Antennae 12 segmented. Scape short, surpassing the vertex by less than one-half scape length. Anterolateral clypeal margin even with the mediolateral region, or occasionally with the corners expanded slightly anterior of the mediolateral region. Anteromedial clypeal margin entire, without a central notch or concavity of any type. Anterior clypeal setae 8-10; short, less than twice the maximum scape diameter; straight. Posterior clypeal margin between the anterior and posterior surfaces of the antennal socket cavities. Anterior tentorial pit nearer the antennal socket than the mandibular insertion. Anterolateral hypostoma reduced to a thin sclerite. Medial hypostoma entire. Psammophore absent. MOUTHPARTS. Palp formula 6:4 or 4:3 (and possibly others, see worker description). Third maxillary palp segment (when present) subequal in length to segment 4. Fifth maxillary palp segment (when present) at the apical extreme of segment 4. Mandible with 7-8 teeth and 0-1 denticles. Apical tooth subequal in length to, to slightly longer than, the subapical tooth. Basal angle distinct, with a well developed tooth or angle separating the masticatory and basal margins. Basal margin varying from smooth (without teeth or denticles) to denticulate along entire surface. MESOSOMA. Posteroventral pronotum lateral, rounded or angled. Episternal suture complete. Mesopleural process absent. Anteromedial mesosternum even with the lateral regions. Axilla subparallel (very weakly constricted), constricted medially, or absent dorsally; when present, entire. Anterior axillar suture (when present) straight or angular medially. Declivitous face of propodeum convex; dorsal face convex, subequal in length to the declivitous face. Propodeal angle indistinct. Propodeal suture absent. Mesosomal spines and tooth absent. Erect mesoscutal hairs about 16-100; short, less than twice the maximum scape diameter to elongate, more than twice the maximum scape diameter. Propodeal spiracle lateral and ventral ofthe propodeal dorsum. Hind tibial spur with well developed barbules along entire inner surface (except extreme base). WINGS. Radial cell closed. Fore wing with 1 cubital and 1- 2 discoidal cells. Hind wing with 2 cells. PETIOLE. Scale present; ridged and with a distinct angle dorsally; strongly inclined anteriorly and with the anterior face much shorter than the posterior face. Venter with a well developed, rounded lobe. GASTER. First segment vertical and not concealing the petiole in dorsal view and with a groove or indentation for the reception of the entire height of the petiole. Fifth tergite vertical and with the distal terminus of the gaster not well defined. Gastral compression absent (gaster circular in cross section). Fourth sternite flat across entire posterior border.

Male

HEAD. I nner margin of eye entire, flat. Scape length shorter than the length of funicular segments 2+3. First funicular segment barrel-shaped. Second funicular segment barrel-shaped, straight. Funicular segments 2 and 3 at most twice as long as broad. Third and fourth funicular segments straight. Anteromedial clypeal margin entire, without a central notch or concavity of any type. Anterior clypeal setae 4-10; short, about as long as the maximum diameter of the scape; straight. Posterior clypeal margin even with or anterior to the anterior surfaces of the antennal socket cavities. Anterior tentorial pit nearer the antennal socket than the mandibular insertion. Anterolateral hypostoma reduced to a thin sclerite. Medial hypostoma entire. MOUTHPARTS. Palp formula 6:4 or 5:3 (and possibly others, see worker description). Third maxillary palp segment subequal in length to segment 4. Fifth maxillary palp at the apical extreme of segment 4. Mandible with 1-4 teeth and 0 - about 3 denticles. Apical tooth distinct. Basal angle indistinct, with a relatively uninterrupted curve between the two margins and without a distinct tooth or angle. Basal margin smooth and without teeth or denticles. MESOSOMA. Posteroventral pronotum lateral, rounded or angled. Episternal suture present, complete. Anteromedial mesosternum even with the lateral regions. Axilla parallel or constricted medially, and entire. Anterior axillar suture straight. Declivitous face of propodeum convex; dorsal face convex, subequal in length to the declivitous face. Propodeal angle distinct. WINGS. Radial cell closed. Fore wing with 1 cubital and 1-2 discoidal cells. Pterostigmal appendage absent. Hind wing with 2 cells. PETIOLE. Scale present; a blunt angle dorsally, or spined with a single tooth or projection dorsally; vertical and not inclined anteriorly. Venter with a well developed lobe. Attachment to gaster broad. GASTER. First segment vertical and not concealing the petiole in dorsal view and with a groove or indentation for the reception of the entire height of the petiole. GENITALIA. Pygostyles vestigial. Posterior margin of subgenital plate convex or even across entire width. Paramere entire. Digitus linear, without a down-turned tip; tip sometimes slightly swollen. Cusp is absent. Ventral lobe of volsella present as a swelling. Aedeagus with ventral teeth.

Larva

Shape crematogastroid. Protuberances present as 2 bosses located ventrolaterally on prothorax. Body hairs sparse and moderately abundant; simple and hooked; short and elongate. 10 spiracular pairs. Antennae large.

References

  • Ashmead, W. H. 1905c. A skeleton of a new arrangement of the families, subfamilies, tribes and genera of the ants, or the superfamily Formicoidea. Can. Entomol. 37: 381-384 (page 384, Azteca in Dolichoderidae)
  • Ayala, F. J.; Wetterer, J. K.; Longino, J. T.; Hartl, D. L. 1996. Molecular phylogeny of Azteca ants (Hymenoptera: Formicidae) and the colonization of Cecropia trees. Molecular Phylogenetics and Evolution 5:423-428. [1996-04] PDF
  • Bolton, B. 2003. Synopsis and Classification of Formicidae. Mem. Am. Entomol. Inst. 71: 370pp (page 83, Azteca in Dolichoderinae, Dolichoderini)
  • Dalla Torre, K. W. von. 1893. Catalogus Hymenopterorum hucusque descriptorum systematicus et synonymicus. Vol. 7. Formicidae (Heterogyna). Leipzig: W. Engelmann, 289 pp. (page 163, Azteca in Dolichoderinae)
  • Dlussky, G. M.; Fedoseeva, E. B. 1988. Origin and early stages of evolution in ants. Pp. 70-144 in: Ponomarenko, A. G. (ed.) Cretaceous biocenotic crisis and insect evolution. Moskva: Nauka, 232 pp. (page 77, Azteca in Dolichoderinae, Tapinomini)
  • Donisthorpe, H. 1943g. A list of the type-species of the genera and subgenera of the Formicidae. [part]. Ann. Mag. Nat. Hist. 11(10): 617-688 (page 627, Azteca in Dolichoderinae, Tapinomini)
  • Duran-Ruiz, C. et al. 2013. Ants from the Miocene Totolapa amber (Chiapas, Mexico), with the first record of the genus Forelius (Hymenoptera, Formicidae). Can. J. Earth Sci. 50, 495-502 (dx.doi.org/10.1139/cjes-2012-0166).*Bolton, B. 1994. Identification guide to the ant genera of the world. Cambridge, Mass.: Harvard University Press, 222 pp. (page 26, Azteca in Dolichoderinae, Dolichoderini)
  • Emery, C. 1895l. Die Gattung Dorylus Fab. und die systematische Eintheilung der Formiciden. Zool. Jahrb. Abt. Syst. Geogr. Biol. Tiere 8: 685-778 (page 771, Azteca in Dolichoderinae)
  • Emery, C. 1913a [1912]. Hymenoptera. Fam. Formicidae. Subfam. Dolichoderinae. Genera Insectorum 137: 1-50 (page 29, Azteca in Dolichoderinae, Tapinomini)
  • Forel, A. 1878c. Études myrmécologiques en 1878 (première partie) avec l'anatomie du gésier des fourmis. Bull. Soc. Vaudoise Sci. Nat. 15: 337-392 (page 384, Azteca as genus; Azteca in Dolichoderinae [Dolichoderidae])
  • Forel, A. 1895b. A fauna das formigas do Brazil. Bol. Mus. Para. Hist. Nat. Ethnogr. 1: 89-139 (page 108, Azteca in Dolichoderinae)
  • Forel, A. 1899f. Formicidae. [part]. Biol. Cent.-Am. Hym. 3: 81-104 (page 104, Azteca in Dolichoderinae)
  • Forel, A. 1917. Cadre synoptique actuel de la faune universelle des fourmis. Bull. Soc. Vaudoise Sci. Nat. 51: 229-253 (page 248, Azteca in Dolichoderinae, Tapinomini)
  • Guerrero, R. J., J. H. C. Delabie & A. Dejean. 2010. Taxonomic contribution to the aurita group of the ant genus Azteca (Formicidae: Dolichoderinae). Journal of Hymenoptera Research. 19(1):51-65. PDF
  • Jaffe, K. 1993. El mundo de las hormigas. Baruta, Venezuela: Equinoccio (Ediciones de la Universidad Simón Bolívar), 188 pp. (page 9, Azteca in Dolichoderinae, Tapinomini (anachronism))
  • Kempf, W. W. 1972b. Catálogo abreviado das formigas da regia~o Neotropical. Stud. Entomol. 15: 3-344 (page 29, Azteca in Dolichoderinae, Tapinomini)
  • Longino, J. T. 1989b. Taxonomy of the Cecropia-inhabiting ants in the Azteca alfari species group (Hymenoptera: Formicidae): evidence for two broadly sympatric species. Contr. Sci. (Los Angel.) 412: 1-16 (page 1, Revisionary study)
  • Longino, J. T. 1991a. Taxonomy of the Cecropia-inhabiting Azteca ants. J. Nat. Hist. 2 25: 1571-1602 (page 1571, Revisionary study)
  • Longino, J.T. 2007. A taxonomic review of the genus Azteca in Costa Rica and a global revision of the aurita group. Zootaxa. 1491:1-63. PDF
  • Shattuck, S. O. 1992c. Generic revision of the ant subfamily Dolichoderinae (Hymenoptera: Formicidae). Sociobiology 21: 1-181 (page 49, Azteca in Dolichoderinae, Dolichoderini)
  • Shattuck, S. O. 1994. Taxonomic catalog of the ant subfamilies Aneuretinae and Dolichoderinae (Hymenoptera: Formicidae). Univ. Calif. Publ. Entomol. 112:i-xix, 1-241. (page 10, catalogue)
  • Wheeler, W. M. 1910b. Ants: their structure, development and behavior. New York: Columbia University Press, xxv + 663 pp. (page 142, Azteca in Dolichoderinae)
  • Wheeler, W. M. 1922i. Ants of the American Museum Congo expedition. A contribution to the myrmecology of Africa. VII. Keys to the genera and subgenera of ants. Bull. Am. Mus. Nat. Hist. 45: 631-710 (page 690, Azteca in Dolichoderinae, Tapinomini)