Azteca aurita

Longino, J. T., 2007, A taxonomic review of the genus Azteca (Hymenoptera: Formicidae) in Costa Rica and a global revision of the aurita group., Zootaxa 1491, pp. 1-63: 54-55

publication ID

21311

publication LSID

lsid:zoobank.org:pub:C31A1226-724D-4D1A-8471-E6BB441EE3EF

persistent identifier

http://treatment.plazi.org/id/BE69B7A1-FC90-049F-3ACE-A41881477A77

treatment provided by

Thomas

scientific name

Azteca aurita
status

 

Azteca aurita  HNS  group

Diagnosis. Queen and worker: Palpal formula 4,3; middle and hind tibia lacking apical spur; anteromedial border of clypeus strongly convex and extending well beyond anterolateral clypeal lobes, HLB/HLA> 1.04. Queen: general body size small, similar in size to major workers; integument extremely smooth and shining, glass-like, with appressed pubescence extremely dilute; pilosity, when present, a stubble of short, stiff, fully erect setae; petiole bluntly subpyramidal to bilobed, never flat and scale-like.

Worker: Head always cordate, with variable tendency for posterolateral portions of occipital border to be drawn out into angular projections; scape, tibiae, lateral and posterior margins of head, and mesosomal dorsum devoid of setae; mandibles either of two forms, both unique to the species group: (1) dorsal surface strongly flattened, densely and finely striate, mat, or (2) dorsal surface convex and shiny, masticatory margin strongly sinuous, with large, projecting apical tooth; petiole as in queen.

Biology. Members of the A. aurita  HNS  species group are widespread but rare. They construct carton nests on the branches of trees, nests which are always bare of epiphytes (they do not form ant gardens).

The diminutive and highly derived queens of the group suggest a social parasitism syndrome (Forel 1928, H√∂lldobler and Wilson 1990). Species in the A. aurita  HNS  group have queens that are about the same size as workers, and the gaster is very small in proportion to the rest of the body. This contrasts with more typical Azteca  HNS  species, which have queens much larger than workers and with large gasters, presumably full of resources for founding new colonies on their own. It is difficult to imagine the small aurita-group  HNS  queens doing so, and a more likely scenario is for aurita-group  HNS  queens to insinuate themselves into established colonies of other species, killing the host queen and having the host workers rear the parasites' offspring. It is not even clear how they function once established; aurita-group  HNS  colonies are enormous, and it seems paradoxical that such small queens could generate sufficient eggs to populate them. The morphology of A. nanogyna  HNS  carries this paradox to an extreme, and a possibility in this case is that A. nanogyna  HNS  is a workerless social parasite.

The A. aurita  HNS  group is perhaps the most circumscribable set of species in the genus, with a distinctive suite of characters. The reduced palpal segmentation and the lack of tibial spurs are both unique to the group and, being losses, are likely apomorphic traits that support the monophyly of the group. The group is most similar to A. trigona  HNS  and A. chartifex  HNS  . Shared worker traits include reduced pilosity, cordate head shape, and the construction of large, pendant, epiphyte-free carton nests. Although many worker series of A. trigona  HNS  have shiny mandibles, a few have faint aciculate sculpture. Also, the mandibles are somewhat flattened, approaching the condition in the A. aurita  HNS  group. Azteca trigona  HNS  workers retain at least a few erect setae on the mesosoma, and often a few setae occur on the tibiae. The queens of the two groups could not be more different. Queens of A. trigona  HNS  are much larger than workers, have broadly cordate heads much wider than long, a mat to sublucid integument, a strongly flattened and scale-like petiole, and no stubbly pilosity.

Knowledge of the taxonomy and natural history of this group is in its incipient stages, but what we do know suggests that additional study would be highly rewarding.

Key to A. aurita  HNS  group queens

1. Color uniform orange; CI> 80 .................................................................................................................... 2

- Color uniform brown; CI <80 ..................................................................................................................... 4

2. Pilosity absent on posterior and posterolateral borders of head, dorsum of mesosoma, petiole, and gaster (tibiae, scape, and all of face and mandibles below level of lower margin of eyes with dense, short, white erect pilosity); HW <1.15mm .............................................................................................................. aurita  HNS 

- Short erect pilosity present on all margins of head and on dorsum of mesosoma, petiole, and gaster; HW> 1.15mm ........................................................................................................................................................ 3

3. Dense, short, erect pilosity on scape and tibiae; head relatively narrower (CI <92) ....................... pilosula  HNS 

- Scape and tibiae lacking erect pilosity; head relatively broader (CI> 92) ................................... lallemandi  HNS 

4. Gastral dorsum lacking erect setae; HLA> 1.35mm ..................................................................... schimperi  HNS 

- Gastral dorsum with erect setae; HLA <1.35mm ....................................................................................... 5

5. HLA about 1.3mm ........................................................................................................................ lanuginosa  HNS 

- HLA about 0.86mm ........................................................................................................................ nanogyna  HNS 

Key to A. aurita  HNS  group workers (the worker of A. nanogyna  HNS  is unknown)

1. Dorsal surface of mandible flat, opaque, densely striate; scape relatively long (SI> 80) .......................... 2

- Dorsal surface of mandible convex, shiny; masticatory margin concave, with enlarged apical tooth; scape relatively short (SI <75) .............................................................................................................................. 3

2. Head relatively broad (CI> 105); posterolateral margins of vertex rounded and cordate, not bluntly angulate................................................................................................................................................. lallemandi  HNS 

- Head relatively narrow (CI <106); posterolateral margins of vertex bluntly angulate ......... aurita  HNS  , pilosula  HNS 

3. Pubescence dilute and tightly appressed; color usually brown with orange head .......................... schimperi  HNS 

- Pubescence more abundant, giving somewhat wooly appearance; color all brown ..................... lanuginosa  HNS 

Kingdom

Animalia

Phylum

Arthropoda

Class

Insecta

Order

Hymenoptera

Family

Formicidae

Genus

Azteca