Cyphomyrmex dentatus Forel, 1966

Kempf, W. W., 1966, A revision of the Neotropical fungus-growing ants of the genus Cyphomyrmex Mayr. Part II. Group of rimosus (Spinola) (Hym. Formicidae)., Studia Entomologica (N. S.) 8, pp. 161-200 : 184-186

9. Cyphomyrmex dentatus Forel , n. stat.

(Figs. 8, 21, 31, 46)

Cyphomyrmex rimosus dentatus Forel , 1901a: 124-5 (Worker; Mexico, Morelos: Cuernavaca). - Wheeler, 1901: 200-1 (Bion.). - Wheeler, 1907: 722-3 (Worker, female; Mexico, Morelos: Cuernavaca). - Skwarra, 1934: 131 (Bion.). - Weber, 1940: 412 (Worker, female; key).

Types. - Workers collected by W. M. Wheeler; deposited in the Forel collection; 5 syntypes from the Wheeler collection (MCZ) examined.

Worker.- Total length 2.9-3.2 mm; head length 0.72- 0.73 mm; head width 0.67-0.69 mm; thorax length 0.93-1.04 mm; hind femur length 0.72-0.77 mm. Rather close to the preceding peltatus , presenting the ensuing differences:

Pale ferruginous yellow, with the front medium brown in color (some specimens, not the types, are a trifle darker). Body hairs minute, appressed, inconspicuous, absolutely not scale-like. Frontal carinae more sinuous. Carinae of vertex rather feeble and blunt. Eyes larger, with about 9 facets across greatest diameter. Scape shorter, not surpassing the somewhat projecting occipital corner by a distance equalling its maximum width (Fig. 8). Pronotum conspicuously but bluntly dentate at antero-inferior corner (Fig. 21). Mesonotal disc rather elongate ellipitical than pentagonal. Mesoepinotal constriction deep. Basal face of epinotum anteriorly with a pair of low tubercles, posteriorly with a pair of triangular prominent teeth. Femora, especially hind femora, deeper (Fig. 46). Petiolar node (Fig. 31) still broader, its sides diverging caudad, its posterior corners bluntly dentate in front of the strongly constricted postpetiolar insertion. Postpetiole relatively shorter and broader. "Tergum I of gaster with the antero-median groove nearly as long as postpetiole; lateral marginations of tergum rather distinct.

Female. - There is a short description by Wheeler (1907: 723) which reads as follows:

"Two dealated females of dentatus in my collection measure 2.4 mm. (a single spread measurement; hence much too low! W.W.K.) in length, and have prominent but blunt and upturned prothoracic spines and strong laterally compressed epinotal teeth; the epinotal declivity is very concave, the posterolateral cones of the postpetiole are more prominent and the median dorsal region of the same segment is more concave than in the worker. The head and thorax are much rougher than in the females of the typical rimosus and the gaster is more strongly tubercular, with a short but deep median depression at the base of the first segment. The body is dark brown, the upper surface of the head and thorax blackish and covered with a bluish bloom".

Male unknown.

Distribution. - So far, this species is only known from the type locality, where it has been repeatedly collected over the years.

Specimens examined: 10 workers as follows: Mexico, Morelos: Cuernavaca, no date, W. M. Wheeler leg. 5 workers (syntypes) and 2 additional workers with the same data but lacking a type label; same locality, June 26, 1928, E. Skwarra leg. 3 workers (MCZ, WWK).

Discussion. - The differences from peltatus were already given above in the differential diagnosis. The dentatus worker differs from rimosus in the following features: Color lighter and body hairs minute and simple. Scapes of antennae short and barely surpassing the occipital angle. Lack of pronotal tubercles. Mesonotum with a shallowly impressed marginate disc, lacking pronounced and prominent tubercles. Anteroinferior pronotal corner dentate. Petiole transverse, with diverging sides, postero-laterally prominent and cone-shaped corners, followed by a pronounced constriction. Postpetiole relatively short and broad with a deep middorsal impression. Epinotum with salient triangular teeth (this latter feature occurs occasionally in some morphs of rimosus , but in this case the remaining features help to separate both species).

The differences for the females are more problematical, since I have not seen any specimens, and Wheeler's description is not sufficient for the diagnosis of isolated females.

At any rate, dentatus seems to me sufficiently distinct from rimosus to be accorded full specific rank.

Bionomics. - According to Wheeler (1901: 200-1), who first collected this species on December 26 (year not given), the species is ''not uncommon along the barrancas where it nests under stones, forming irregular chambers about the roots of the grasses. There are sometimes two queens in a nest. The older and darker queens and workers have the head and thorax covered with a bluish bloom. C. rimosus (Wheeler obviously refers to the present form which he considered as a mere race of rimosus ! W.W.K.) is said not to cultivate mushroom gardens, but this is scarcely correct. They certainly collect caterpillar excrement and on this they grow a peculiar fungus which is not in the form of a white mycelium, like that cultivated by some other species of Cyphomyrmex ( C. wheeleri Forel , for example) but consisting of clusters of small orange yellow, spherical or pyriform nodules about 5 mill. (= 0.5 mm?) in diameter. The exhausted masses of caterpillar excreta are piled on the refuse heap in a distant corner of the nest. The eggs of C. rimosus (again the present form is meant! W.W.K.) are very broad and short, almost spherical''.

Dr. Skwarra (1934: 131) rediscovered the same species at Cuernavaca, finding two earth nests, one of them in the loosely heaped up refuse of Atta nests. She surmises that dentatus possibly uses this material as substrate for its own fungus.