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Costa Rica (Corcovado National Park and Monteverde, both Pacific slope sites).
Cyphomyrmex dixus has only been collected a few times. The type series was collected at 1100m elevation on the Pacific slope just below Monteverde (below Stucky farm on road to San Luis). The habitat was scrubby vegetation and pasture edges. The nest was in a cavity in the trunk of a small tree, about 1m above the ground. Two other collections were made in Sirena, Corcovado National Park. Nests were beneath epiphyte mats in the canopies of forest trees.
This species shares general habitus and arboreal tendencies with C. major. The overall size of the body and the shape of the teeth on the posterolateral vertex margins are similar. The two species appear to be allopatric or parapatric, with dixus being a Pacific slope form and major being an Atlantic slope form.
Snelling, R. R., and J. T. Longino. 1992. Revisionary notes on the fungus-growing ants of the genus Cyphomyrmex, rimosus group (Hymenoptera: Formicidae: Attini). Pages 479-494 in D. Quintero and A. Aiello, editors. Insects of Panama and Mesoamerica: selected studies. Oxford University Press, Oxford. xxii + 692 p.
Diagnosis. Worker only: A member of the rimosusHNS subgroup and most similar to C. minutusHNS, with which it is sympatric; differs from C. minutusHNS and other species in the rimosusHNS 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.
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.
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. rimosusHNS group, only C. flavidusHNS, C. wheeleriHNS and C. bicarinatusHNS possess propodeal spines. In C. flavidusHNS, midpronotal tubercles are absent and the metafemur is abruptly dilated and carinate on the ventral margin. The propodeal spines of C. wheeleriHNS project from a pair of submedian carinae (absent in C. dixusHNS), in C. wheeleriHNS 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. bicarinatusHNS this species differs in lacking occipital spines and in possessing supraocular tubercles.
Found most commonly in these habitats: 1 times found in Scrubby veg. and pasture edge, 1 times found in rainforest, 1 times found in 2nd growth veg., 1 times found in mature wet forest, 1 times found in 2nd growth forest, 1 times found in lowland rainforest, 1 times found in montane forest edge, matrix of forest and pasture land, 1 times found in montane raiinforest edge, 1 times found in montane wet forest.
Found most commonly in these microhabitats: 1 times Colony nesting in cavity in the base of a very hard wood tree trunk, about 1m above ground, 1 times Sloanea canopy, nest under epiphytes, 1 times on vegetation, 1 times nest under loose bark, 1 times on tree trunk, 1 times in Malaise trap, 1 times in canopy of Sloanea, 1 times ex sifted leaf litter, 1 times collected under log, 1 times beating veg..
Collected most commonly using these methods: 2 times search, 1 times beating, 1 times Malaise, 1 times maxiWinkler.
Elevations: collected from 10 - 1575 meters, 811 meters average
Type specimens: nidotype Cyphomyrmex dixus: jtlc000005438, jtlc000005439, jtlc000005440, jtlc000005441, jtlc000005442, jtlc000005443, jtlc000005444, jtlc000005445; paratype Cyphomyrmex dixus: jtlc000005446, jtlc000005447; paratype of Cyphomyrmex dixus: casent0901670