1. Posterior half or more of head disc-like, subcircular in outline, margins forming strong, continuous or nearly continuous raised crest (Fig. 2)



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Basiceros


Diagnosis: The workers and females of this genus can be recognized as medium-sized ants with trapezoidal shaped heads. occasionally the head is elongated. The occipital and lateral borders are not produced into a continuous or near continuous flange or crest around back of the cranium. The eyes are well-developed. The mandibles are triangular, with straight, opposable, multidenticulate masticatory borders. The blade is narrowed into a peduncle at the point of insertion, leaving a large interspace between the basal mandibular and anterior clypeal borders. The labrum is large and well-developed. The antennal scape is flattened and moderately lobate; there are a total of 12 segments. The metanotal groove is well-developed, the propodeal teeth are short, more or less at acute, and connected by a transverse carina. The dorsum of the gaster has a medial, longitudinal strip which is impressed or devoid of pilosity. The pilosity is conspicuous and bizarre, oppressed hairs are abundant, other hairs are spatulate

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Fig. 1. Side view of a worker of B. conjugans (modified from Brown, 1974).

Fig. 2. Two types of hairs of a worker of Basiceros manni (from Brown and Kempf, 1960).

Key to workers and females of Basiceros1,2
1. Posterior half or more of head disc-like, subcircular in outline, margins forming strong, continuous or nearly continuous raised crest (Fig. 2) ……. 2
- Posterior half of head trapezoidal or subrectangular, not disc like, lateral borders of vertex distinct from posterior border, and not forming continuous semicircular crest (Fig. xxx) ………. 3
2(1).
When head is viewed full-face, arcuate crest or flange around back of vertex is medially emarginate and confluent at this point with median convexity of vertex southeastern Brazil, subandean Colombia) ……….. discigera

Fig. 3. Head of a worker of Basiceros discigera (from Brown and Kempf, 1960).

Fig. 4. Mesosoma, petiole and postpetiole of a worker of Basiceros discigera (from Brown and Kempf, 1960).

- Arcuate crest around back of vertex continuous and entire, and separated from median convexity of vertex by broad, uninterrupted sulcus that follows crest; Trinidad ……………………………..… militaris



Fig. 5. Head of a worker of Basiceros militaris (from Brown and Kempf, 1960).

3(1). Labrum shield-shaped piece with rounded free margin, not divided medially, at least on its dorsal (extensor) face ………………………..…………. 4

- Labrum narrow, cuneiform, tapered apicad and with distinct median division or groove ……………..…….. 5



4(3). Head narrow (CI < 75) and nearly parallel-sided; clypeus and mandibles with abundant and conspicuous appressed squamiform hairs; petiole with 1 - 3 ventral processes, and usually at most 1 of these is well-developed and spiniform; base of first gastral sternite with short, but sharp, angulate longitudinal carina; Trinidad to northern Mato Grosso) ……………… ……………………………… singularis

Fig. 6. Head of a worker of Basiceros singularis (from Brown and Kempf, 1960).



Fig. 7. Petiole and postpetiole of a worker of Basiceros singularis (from Brown and Kempf, 1960).

- Head wider (CI > 75), more triangular; clypeus and mandibles with punctures, but no appressed hairs; petiole with 4 - 7 ventral processes, usually all or nearly all slender spiniform; base of first gastric sternite without sharp longitudinal carina; Central America ……………...... manni



Fig. 8. Head of a worker of Basiceros manni (from Brown and Kempf, 1960).



Fig. 9. Petiole and postpetiole of a worker of Basiceros manni (from Brown and Kempf, 1960).

5(3). Posterior dorsal half of head (vertex) continuously convex except for median sulcus; head wide, worker CI > 90; petiole and postpetiole with scanty pilosity, not hiding sculpture; 1 subpetiolar process; southeastern Brazil ……………………..……... convexiceps


Fig. 10. Head of a worker of Basiceros convexiceps (from Brown and Kempf, 1960).

Fig. 11. Petiole and postpetiole of a worker of Basiceros convexiceps (from Brown and Kempf, 1960).

- Vertex with raised lateral margins and median sulcate tumosity; CI < 90; petiole and postpetiole covered densely with fat squamiform hairs that conceal surface; 4 - 6 subpetiolar processes; western Amazon Basin, (Figs. 1, 2) …………………….….. conjugans
Key to Males of Three Species of Basiceros1,2
1. Viewed full-face, head with broad, drawn-out neck longer than space occupied by ocellar triangle; mesokatepisternum opaque, covered by strong interlocking rugae; petiole about 3X as long as postpetiole; Trinidad to northern Mato Grosso ……. singularis 3

- Viewed full-face, head not produced behind, though with flange along cervical margin that is much shorter than ocellar triangle; mesokatepisternum finely punctate, sometimes with upper part smooth and more or less shining; petiole about twice as long postpetiole ………..………….. 2



2(1). Anterior medial border of clypeus concave; more than half of mesanepisternum smooth, and even punctate part strongly shining; upper middle part of mesokatepisternum smooth and shining; western Amazon Basin …………………..…... conjugans

- Anterior border of clypeus entire; only anterior half of anepisternum smooth and shining, remainder densely punctate and nearly opaque; mesokatepisternum densely punctate throughout, only weakly shining in upper middle part between punctures southeastern Brazil, subandean Colombia ……….………….. discigera 4




Basiceros manni xx
Figs. ; Map

Discussion.

Distribution.

Map 1. Basiceros manni.

Habitat.

Biology.

Literature Cited

Brown, W. 1974. A supplement to the revision of the ant genus Basiceros (Hymenoptera: Formicidae). J. New York Entomol. Soc. 82:131-140.

Brown, W. and W. Kempf. 1960. A world revision of the ant tribe Basicerotini. Studia Entomol. (New Series) 3:161-250.





1 From Brown (1974), see also Brown and Kempf (1960)

2 Note: B. redux (Rhopalothrix) not included in keys, see Bolton (1995:80)

3 B. manni from Central America would probably key out here, though the head and petiole may be somewhat shorter than in B. singularis.


4 B. militaris from Trinidad, possibly ocurring also on the mainland, and B. convexiceps from SE Brazil probably key to couplet 2



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