Cyphomyrmex dixus, Snelling, R. R. & Longino, J. T., 1992

Snelling, R. R. & Longino, J. T., 1992, Revisionary notes on the fungus-growing ants of the genus Cyphomyrmex, rimosus-group (Hymenoptera: Formicidae: Attini)., Insects of Panama and Mesoamerica: selected studies., Oxford: Oxford University Press, pp. 479-494 : 489

Cyphomyrmex dixus , new species (Figs 30.3, 30.11, 30.18)

Diagnosis. Worker only: A member of the rimosus subgroup and most similar to C. minutus , with which it is sympatric; differs from C. minutus and other species in the rimosus subgroup in the presence of well-defined, spine-like propodeal tubercles, but with other mesosomal tubercles (except lateral pronotals) low and obtuse. The sexual forms are unknown.

Description

Worker holotype. Measurements: Total length 3.08 (3.07- 3.28); head length 0.73 (0.70-0.79); head width 0.67 (0.63- 0.73); mesosoma length 1.07 (1.03-1.10); metafemur length 0.95 (0.90-0.97) mm. Blackish, grading to brownish ferruginous on lower side of mesosoma, on legs tibiae darker, petiole, and post-petiole; flagellum and mandibles dull ferruginous. Integument opaque throughout, minutely granulose.

Head shape as in Fig. 30.3. Mandible very finely longitudinally lineolate; margin with five teeth. Anterior margin of clypeus very weakly convex and without median notch; parafrontal tooth inconspicuous, bluntly triangular. Frontal area weakly impressed. Frontal lobe broadly rounded and corner above parafrontal tooth rounded; dorsal portion of frontal carina weakly sinuate and attaining occipital corner. Submedian carinae of vertex short, obtuse, and subparallel. Postocellar carina present, but low and vaguely indicated, extending to occipital corner. Supraocular tubercle low, obtuse. Occipital corner not at all produced and occipital tubercle absent (i.e. there is no tubercle present on side of occiput behind occipital corner). Occipital margin broadly concave. Posterior genal margin carinate to base of mandible. Scape projecting beyond occipital corner by less than its greatest thickness; funicular segments 2-8 about as long as broad. Eye with 10- 12 facets along greatest diameter; oculomandibular distance 1.07-1.08 times eye length.

Mesosomal profile as in Fig. 30.11. Submedian pronotal tubercules present but very weak; lateral tubercle short and bluntly triangular; humeral ridge anterior to lateral tubercle low and rounded. Disc of mesonotum weakly concave; anterior tubercle low and blunt; posterior tubercle low, bluntly triangular. Mesometanotal impression deep and narrow. Dorsal ridges of propodeum weak; posterior face with a pair of spine-like, subacute tubercles that are longer than broad at base. Ventral margin of metafemur subangularly dilated at basal one-third, but without definite carina distally of dilation.

Petiole and post-petiole as in Fig. 30.18. Node of petiole depressed and about twice broader than long. Postero-median depression of post-petiole moderately deep. Antero-median depression of first gastric tergum longer than broad, weakly defined.

Pilosity flattened, scale-like, and appressed on most surfaces; gastral venter with sparse, suberect to erect, long, slender hairs.

Type material

Holotype and 197 paratype workers (some preserved in alcohol): Monteverde, 10° 18' N, 84° 39'W, 1100 m, elev. Puntarenas Province, costa rica, 7 Aug. 1985 (J. Longino, No. 691), in Natural History Museum of Los Angeles County. Paratypes in BMNH, LACM, LONG, MCZ, and USNM.

Etymology. The specific epithet is of Greek origin and means double, referring to the pair of propodeal spines.

Discussion. Additional specimens (not paratypes) are from Parque Nacional Corcovado, Sirena, 18° 28'N, 83° 35' W, 0- 100 m, elev. Puntarenas Province, 1 and 11 July 1982 (J. Longino).

Within the broad C. rimosus group, only C. flavidus , C. wheeleri and C. bicarinatus possess propodeal spines. In C. flavidus , midpronotal tubercles are absent and the metafemur is abruptly dilated and carinate on the ventral margin. The propodeal spines of C. wheeleri project from a pair of submedian carinae (absent in C. dixus ), in C. wheeleri the preocular carina does not curve mesally in front of the eye, and the node of the petiole bears an apical tooth in lateral view. From C. bicarinatus this species differs in lacking occipital spines and in possessing supraocular tubercles.