Gnamptogenys perspicax

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Gnamptogenys perspicax
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Ectatomminae
Tribe: Ectatommini
Genus: Gnamptogenys
Species: G. perspicax
Binomial name
Gnamptogenys perspicax
Kempf & Brown, 1970

Gnamptogenys perspicax P casent0281217.jpg

Gnamptogenys perspicax D casent0281217.jpg

Specimen Label

The types were from collected from a colony nesting in a large rotten log. Gnamptogenys perspicax a millipede feeding species found in humid forests.

Identification

A member of the bispinosa complex (in the rastrata subgroup of the rastrata species group). Apparently a sister species of Gnamptogenys bispinosa. Eye slightly behind cephalic mid-length; scape longitudinally striate with abundant standing hairs; petiole node more or less evenly convex; postpetiolar sternum with transverse costulate or rugae. (Lattke 1995)

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Neotropical Region: Colombia (type locality), Ecuador.

Distribution based on AntMaps

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Distribution based on AntWeb specimens

Check data from AntWeb

Biology

Kempf and Brown (1970) - The type nest of G. perspicax was taken in a heavily shaded ravine in cloud forest about 50 m off the road into Pichindé Valley, southwest of Cali and at an elevation of about 1570 m. The nest was in a large rotten log lying on the ground, but with one large branch raised off the ground about 1.5 m; the nest was in the end of the branch, and consisted of 4-5 chambers of different sizes (all more than 2 cc volume) and a very large nest entrance at the open free stub-end of the branch, more than 4 cm in diameter. The lip of the nest opening and the ground beneath was strewn with the bleached remains of large millipeds, and freshly cut-up milliped prey specimens were found within, being fed upon by the ant larvae. No other kinds of prey could be found in or around the nest. Most of the nest, with its ergatoid queen and some larvae, were brought to the United States for observation, and subsequent tests showed that live-caught millipeds are far and away the preferred food of G. perspicax, and probably its only food in natural circumstances. The ant is resistant to the defensive cyanide released by some millipeds, particularly polydesmoids. This resistance, and the utilization of millipeds for food by perspicax and related species of Gnamptogenys, will be discussed in another paper. The nest as found contained about 45 adult workers and the single queen.

Castes

Nomenclature

The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.

  • perspicax. Gnamptogenys perspicax Kempf & Brown, 1970: 316, figs. 3-5 (w.q.) COLOMBIA.

Gnamptogenys perspicax is close to Gnamptogenys bispinosa from Costa Rica, differing principally in the black color, longer mandibles, shorter and much broader head, narrower and less protruding occipital flange, much shorter and more strongly raised propodeal spines, more prominent and subglobose eyes. The differences from the triangularis-group (formerly subgenus Parectatomma) include larger size, much more irregular sculpture; long propodeal teeth; conspicuous (not obsolete) promesonotal suture; transversely sculptured mesonotum; strongly constricted frontal lobes; strikingly protruding eyes; very long antennal scapes. In fact, G. perspicax is a perfect intermediate between the triangularis group, particularly such species as Gnamptogenys mecotyle and Gnamptogenys schubarti (=Gnamptogenys menozzii), and the somewhat aberrant Gnamptogenys bispinosa. The new species also helps to close up the morphocline connecting the triangularis group and the schmitti group (formerly Emeryella). Had Parectatomma and Emeryella not already been synonymized with Poneracantha in the genus Gnamptogenys, the discovery of G. perspicax would surely have forced the change even in the most conservative classification.

G. perspicax is not easily accommodated in the key of Brown (1958: 230) to the New World species of Gnamptogenys. It might logically come out in couplet 1 with bispinosa, but the propodeal teeth are not quite long enough. If we go on, we come to couplet 6, where the rather distinct promesonotal suture of perspicax might lead us to the otherwise quite different striatula group (formerly Holcoponera), were it not that the suture fails to break the sculpture. Moving on, we end in the triangularis group, and perspicax keys out uneasily to mecotyle (and is also similar to Gnamptogenys lanei of Kempf 1960). The characters already listed above will readily separate perspicax from these and other members of the triangularis group.

Description

Worker

holotype - Total length 9.5 mm; maximum length of head capsule 2.00 mm; maximum width of head in front of eyes 1.95 mm; scape length 2.15 mm; maximum diameter of eyes 0.35 mm; maximum width between frontal lobes 0.78 mm; Weber's length of truncus 3.08 mm; hind femur length 2.67 mm; petiole length 0.82 mm; petiole width 0.77 mm; postpetiole (segment I of gaster) length 1.38 mm; postpetiole width 1.53 mm. Black; mandibles, antennae, legs except coxae reddish brown. Retractile apical gastric segments yellowish brown. Shining throughout in spite of sculpture. Body and appendages with abundant pale standing hairs which mostly equal or exceed in length the maximum diameter of eyes; those that fringe the anterior border of clypeus are longer. Pubescence scarce, practically invisible except on funiculi, flexor face of tibiae, tarsi and underside of petiole.

Kempf Brown1970 Ectatommini.jpg

Head. - Mandibles elongate-subtriangular; basal border much shorter than apical border; outer border sinuous; chewing border with approximately 15 small, triangular denticles, often worn down, except for the strong apical tooth; basal angle obtuse. Dorsum longitudinally costulate; costular count across greatest width 8-10. Palpi 3,2.

Head capsule nearly as broad as long, broader in front than behind; clypeus convex, with a modest median sulcus and a narrow, nearly straight-edged anterior apron that has its antero-lateral angles gently rounded; disc with 16 longitudinal costae. Frontal area impressed. Frontal lobes convex, short, not covering completely the antennal sockets when seen from above, obliquely raised laterad, strongly constricted behind. Frontal carinae very short, obliquely diverging caudad, fading out in front of eyes. Lateral borders of head gently convex, converging caudad. Occipital border practically straight; occipital corners broadly rounded. Eyes subglobose, protruding, with a circummarginal sulcus, with about 20 facets across the greatest diameter. Front between carinae with about 12 longitudinal costae that tend to spread out fan-like posteriorly, where they become irregular and anastomose occasionally among each other, with deeper foveae between the costae or within the meshes. Sides of head rugose to reticulate-rugose. Occiput with 3-4 transverse costae above the foramen. Occipital flange narrow but conspicuous. Gula with longitudinal, irregular costae; costae of both sides converging in front and fusing with one another in a semicircular fashion.

Antennal scapes slender, longer than head capsule proper, greatly projecting beyond occiput; shining, finely striate. All funicular segments longer than broad, decreasing in length and increasing in thickness towards apex; apical segment twice as long as the subapical segment.

Truncus as shown in figure 4. Dorsal surface of pronotum transversely costate in front, longitudinally behind, the anterior transverse costae (12) curve caudad on sides, the mesial ones flanking the 5 postero-median longitudinal costae, the lateral ones continuing horizontally and more irregularly on sides of pronotum. Promesonotal suture distinctly impressed but not interrupting the sculpture pattern: the 6-7 transverse costae of mesonotum close the circle around the posteromedian costae of pronotal disc. Metanotal groove deeply impressed. Dorsum of propodeum transversely convex, transversely costate, about 16 costae in front of the strongly raised and pointed propodeal spines; the latter about half as long as their distance between their inner faces at base. Propodeal stigma round, slightly protruding. Mesepisternum with the usual narrow anterior flange, its surface irregularly costate-rugose. Rest of sides of truncus, except posteriorly where horizontal costae predominate, rather irregularly costate-rugose. Declivitous face of propodeum transversely costate. All costae slightly to conspicuously vermiculate, in the latter cases with frequent anastomoses. Piligerous pits usually conspicuous and impressed. Fore coxae regularly horizontally costate, as are the upper surfaces of the middle and hind coxae; the latter with a strong basidorsal spine. Legs long, slender, smooth and shining. Extensor face of tibiae finely longitudinally striate. Tarsal claws of all legs with a well-developed subapical tooth.

Petiole (fig 4) low, longer than broad (but the node proper slightly broader than long), transversely costate above, with about 18-20 costae across the dorsum, the anterior and posterior ones becoming horizontal on sides, encircling the mesial ones. Subpetiolar process plate-like, with anterior and posterior corners rectangular and slightly pointed, the inferior border gently emarginate.

Gaster as shown in figure 4. Tergum I (postpetiole) with about 12-14 transverse vermiculate-costate ridges in front, the lateral continuations horizontal, enclosing a few (3-5) postero-median longitudinal short costae that occupy the posterior third of the dorsal length of the segment. Sternum I transversely vermiculate-costate, anteroventral process entire. Tergum II with 45-50 longitudinal costae that are more regular; extreme lateral ones somewhat vermiculate; piligerous pits inconspicuous. Sternum II with finer rugae that converge mesally behind.

Worker variation. - 29 workers closely examined from the type nest series are nearly identical for all practical purposes, except for small details of sculptural pattern. The head varies from slightly longer than wide to slightly wider than long, but this depends somewhat on the exact viewing angle. The range of critical measurements for the type series is as follows: Total length 9.0-9.6 mm; head length 1.86-2.00 mm; head width 1.86-2.00 mm; scape length 2.15-2.26 mm; maximum diameter of eye 0.34-0.38 mm; Weber's length of truncus 2.90-3.13 mm; hind femur length 2.51-2.72 mm; petiole length 0.82-1.00 mm; length of petiolar node excluding anterior cornuae 0.64-0.81 mm; petiole width 0.72-0.82 mm; postpetiole length 1.33-1.44 mm; postpetiole width 1.48-1.60 mm. Two workers dissected each had 6 malpighian tubules.

Queen

Ergatoid - Total length 8.6 mm; head length 1.67 mm; head width in front of eyes 1.60 mm; mandible length, straight line, outer base to apex, 1.40 mm; scape length 1.60 mm; maximum diameter of eye 0.28 mm; Weber's length of truncus 2.45 mm; hind femur length 2.00 mm; petiole length 0.80 mm; length of petiolar node (without anterior cornuae) 0.58 mm; width of petiolar node 0.88; postpetiolar length 1.24 mm; postpetiole width 1.90 mm.

Body overall smaller than in any of the workers of the same nest series, but gaster both relatively and absolutely broader and deeper, decidedly broader than the head. (In workers, head is broader than gaster). Truncus short and stocky; antennae and legs shorter than in worker, and eyes a little smaller; anterior ocellar pit well developed but without lens; other ocelli obsolete. Head feebly convex behind in full-face view. Propodeum shorter, more convex above than in worker, and petiolar node both shorter and wider. Pilosity and sculpture much as in worker (hairs perhaps a bit longer and more abundant, costulae sometimes slightly more crowded); color piceous black; antennae, legs, mandibles and gastric apex ferruginous yellow.

This peculiar queen outwardly resembles mermithergate individuals of some other ponerine ants so closely that the gaster was dissected; it proved to contain no parasite, but only what appeared to be the dried remains of the usual ant abdominal organs.

Type Material

29 workers and one ergatoid queen from Colombia, Valle Dept., Pichindé Valley, SW of Cali, 1570 m, March 22, 1967, R. B. Root and W. L. Brown, Jr. leg. holotype and paratypes deposited in Museum of Comparative Zoology, Cornell University collection and WWK).

References

  • Kempf, W. W.; Brown, W. L., Jr. 1970. Two new ants of tribe Ectatommini from Colombia (Hymenoptera: Formicidae). Stud. Entomol. 13: 311-320 (page 316, figs. 3-5 queen described). PDF
  • Lattke, J. E. 1995. Revision of the ant genus Gnamptogenys in the New World (Hymenoptera: Formicidae). J. Hym. Res. 4:137-193.