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 View in CoL   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) - workers GoogleMaps ; Cedral, Corcovado National Park , 8°33'N, 83°33'W, 5m , 12 Feb 1996 (J. Longino) - workers GoogleMaps ; PANAMA: Canal Zone: Pipeline Road , 9°07'N, 79°44'W, 50m , 10 Sep 1990 (D. M. Olson) - worker GoogleMaps .


Switzerland, Geneva, Museum d'Histoire Naturelle


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













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