Azteca chartifex Forel,

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: 23-25

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Azteca chartifex Forel


Azteca chartifex Forel  HNS  1896

Figure 7.

Azteca chartifex Forel  HNS  , in: Emery 1896b:4. Syntype workers: Trinidad (Urich) [ MHNG, MCZC]  (examined).

Azteca chartifex race laticeps Forel  HNS  1899:117. Syntype workers: Costa Rica (Tonduz)  ; and Panamá, Bugaba, Volcan de Chiriqui (Champion) [ MHNG]  (examined). Further description of workers: Forel 1906:236. NEW SYNONYMY

Worker characters.Measurements (n=5 workers from Costa Rica to Brazil): HLA 0.88 (0.84-0.96), HW 0.97 (0.87-1.05), SL 0.78 (0.64-0.85), CI 108 (100-110), SI 87 (74-89).

Palpal formula 5,3; middle and hind tibia with prominent pectinate apical spur; dorsal surface of mandible smooth and shining, with moderately abundant small piligerous puncta; medial and lateral clypeal lobes at about same level; head with strongly convex sides, strongly cordate posterior margin; in lateral profile promesonotum forming single strongly protruding convexity, posterior mesonotum dropping abruptly to much lower metanotal groove and dorsal face of propodeum; scape and tibia lacking erect setae; sides and posterior margin of head lacking erect setae; posterior pronotum with conspicuous cluster of 6 or more long erect setae, mesonotum with 0-4 shorter erect setae, dorsal face of propodeum with 4-6 erect setae at variable angles to surface; color red brown.

Range. Costa Rica to southern Brazil.

Biology. Azteca chartifex  HNS  occurs in wet forest habitats. Colonies are polydomous, occurring in clusters of large, pendant carton nests. The carton is dry and paper-like. The nests are never penetrated by epiphytes or other plant roots, and in this regard are very different from the ant gardens of A. gnava  HNS  and A. nigra  HNS  . They can occur in very exposed and highly insolated environments, and seem more abundant in seasonal moist to dry habitats than in weakly seasonal wet forest.

I have observed two colonies in Costa Rica, both in the lowland forest of the Osa Peninsula. Both colonies were in regenerating second growth forest. One colony was on a large Inga  (Fabaceae) tree and several adjacent Psidium  (Myrtaceae) trees. There were about eight large nests within a 10m radius. Individual nests were up to 2m long and tapering. I cut into several nests and dissected one nest thoroughly, finding only workers and larger brood. This particular colony was relatively long-lived: I first observed it in 1990, and when I walked by the same site six years later the colony was still there and looked relatively unchanged. The second colony I observed was a single large nest on a palm trunk, about 10m high. It was in an area of dense vegetation and it is likely there were other nests in the vicinity. Forel's subspecies laticeps  HNS  was collected from a carton nest on Psidium  (the Champion series from Chiriquí, Panamá).

Comments. The production of large pendant carton nests by Azteca  HNS  is a common phenomenon in moist to wet forests from Panama southward through tropical South America. Some of them are made by the A. aurita  HNS  group (see Addendum), but the majority are made by the A. trigona  HNS  group. The workers of the A. trigona  HNS  group exhibit a strongly hump-shaped promesonotum (Fig. 7: chartifex  HNS  ) which drops steeply and abruptly to the much lower dorsal face of the propodeum. Other characters exhibited by but not unique to the group are 5,3 palpal formula, prominent meso and metatibial spurs, broad heads (CI> 99), and few to no metatibial setae which, if present, are very short and inconspicuous. The queens have very broad, strongly cordate heads (CI 109-135). The only other Azteca  HNS  queens with heads that proportionately broad are A. gnava  HNS  , which have strongly setose tibia and a 6,4 palpal formula. The species group as a whole has a sharp geographic boundary: it is common in central Panama, but Costa Rica is the far northern limit of the group, with a single rare species in the southern Pacific lowlands.

The species-group taxa associated with this group are A. trigona  HNS  and its synonyms and infraspecific forms festai  HNS  , gaigei  HNS  , mathildae  HNS  , mediops  HNS  , subdentata  HNS  ; A. chartifex  HNS  and its infraspecific forms cearensis  HNS  , decipiens  HNS  , lanians  HNS  , laticeps  HNS  , multinida  HNS  , spiriti  HNS  , stalactitica  HNS  ; A. barbifex  HNS  ; and A. severeni  HNS  . Queens are known for only two of these: A. trigona  HNS  and A. barbifex  HNS  . I have examined the types of most of the taxa and made measurements of HLA, HW, and SL. When the data for workers are all plotted together, they form one continuous cloud of points along one line of allometry. However, when I examine just series from Panama and Costa Rica, two groups emerge. One group has the largest workers (selecting one of the larger workers of each series) with HW 1.21-1.36mm, CI> 111, and the posterior margin of the head with a very deep, V-shaped medial impression. Another group has the largest workers with HW 0.93-1.06mm, CI <111, and the posterior margin of the head with a shallower, less strongly V-shaped medial impression. The former I identify as A. trigona  HNS  ; the latter as A. chartifex  HNS  . The various subspecies of A. trigona  HNS  and A. chartifex  HNS  fall within these respective size ranges, with the exceptions of A. trigona gaigei  HNS  , with HW 1.06mm, and A. chartifex lanians  HNS  , with HW 1.22mm. Azteca severeni  HNS  , with HW 1.11mm, is intermediate.

Queens are remarkably rare in this group. I have been able to examine and measure eight queens, including the holotype queen of A. trigona  HNS  and the syntype queen of A. barbifex  HNS  . Six of the queens, which I identify as A. trigona  HNS  , form a cluster with HW 1.64-1.82mm. A queen from Bolivia has a very broad head, with HW 2.07mm, and the queen of A. barbifex  HNS  is distinctly smaller, with HW 1.20mm. Azteca barbifex  HNS  workers are similar in size and shape to A. chartifex  HNS  workers. Thus it is possible that there are two main lineages, A. trigona  HNS  having large queens and workers, and A. chartifex  HNS  having small queens and workers. Azteca barbifex  HNS  workers fall well within the cloud of points formed by A. chartifex  HNS  and its subspecies.

The very broad heads and short, small mandibles suggest very powerful cutting ability, like bolt cutters. Perhaps Azteca trigona  HNS  group queens found their nests in hard dead wood, and this head structure is an adaptation for quickly excavating a chamber in hard wood.

Additional material examined. COSTA RICA: Puntarenas: Sirena, Corcovado National Park , 8°29'N, 83°36'W, 5m , 16 Dec 1990 (J. Longino) - workersGoogleMaps  ; Cedral, Corcovado National Park , 8°33'N, 83°33'W, 5m , 12 Feb 1996 (J. Longino) - workersGoogleMaps  ; PANAMA: Canal Zone: Pipeline Road , 9°07'N, 79°44'W, 50m , 10 Sep 1990 (D. M. Olson) - workerGoogleMaps  .


Switzerland, Geneva, Museum d'Histoire Naturelle


USA, Massachusetts, Cambridge, Harvard University, Museum of Comparative Zoology