Octostruma iheringi

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Octostruma iheringi
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Attini
Genus: Octostruma
Species: O. iheringi
Binomial name
Octostruma iheringi
(Emery, 1888)

Octostruma iheringi casent0178700 profile 1.jpg

Octostruma iheringi casent0178700 dorsal 1.jpg

Specimen Label

Synonyms

Octostruma iheringi is a widespread lowland species. In Central America it occurs in wet to seasonally dry habitats, in both mature and second growth forest, from sea level to about 800 m elevation. Almost all collections are from Berlese and Winkler samples of sifted litter and rotten wood from the forest floor. Dealate queens occasionally occur together with workers in litter samples. An alate queen was taken in July 1997, in the lab clearing of La Selva Biological Station, Costa Rica, a lowland rainforest site. (Longino 2013)

Identification

Keys including this Species

Distribution

Southern Mexico to southern Brazil, Jamaica.

Distribution based on Regional Taxon Lists

Neotropical Region: Bolivia, Brazil (type locality), Colombia, Costa Rica, Ecuador, Greater Antilles, Guatemala, Honduras, Jamaica, Mexico, Nicaragua, Panama, Paraguay, Trinidad and Tobago, Venezuela.

Distribution based on AntMaps

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Distribution based on AntWeb specimens

Check data from AntWeb

Biology

Longino (2013) - Brown and Kempf (1960) summarized the biology of basicerotines as follows: The basicerotines all come from tropical or subtropical areas, and predominantly from mesic habitats, particularly rain forest, where they live primarily in the upper layers of the soil and in the soil cover, including large and small pieces of rotten wood. They are fairly common in soil cover berlesates. Nests have been found in snail shells, and in the peaty masses gathered about epiphytic ferns above the ground level. So far as is known, colonies are small, consisting of one or more dealate—or rarely ergatoid—females, and a few workers. Judging from the structure of the workers and females, one would suppose that they were predaceous on small arthropods...

Besides this summary, the behavior of three basicerotine species has been studied. Wilson (1956) observed a small captive colony of Eurhopalothrix biroi, a New Guinea species. Workers moved slowly and captured a variety of small, soft-bodied prey, including spiders, symphylans, entomobryid Collembola, campodeids, and hemipteran nymphs. Wilson and Brown (1984) observed a captive colony of Eurhopalothrix heliscata, a species from Singapore. The colony contained over 400 workers, multiple alate and dealate queens, several adult males, and brood. Foraging workers acted "rather like miniature ferrets," readily wedging themselves into small crevices. They foraged solitarily, attacking a variety of prey but mostly termites. They used their sharply-toothed mandibles to abruptly snap onto appendages of prey, maintaining purchase and slowly reaching around with the gaster to sting the prey. The strongly sclerotized labrum was also employed to press against the clamped appendage. The behavioral repertoire was limited. There did not appear to be trophallaxis, as workers and larvae fed directly from prey in the brood chambers. Nor did there appear to be any form of alarm communication. While there was generally an increase in the number of foragers when clusters of prey were presented, there was no evidence of any pheromone-based recruitment. Workers were non-aggressive and responded to disturbance by tucking the appendages and becoming immobile, often for minutes at a time. Wilson and Hölldobler (1986) studied captive colonies of Basiceros manni from Costa Rica and observed behavior not substantially different from E. heliscata. Foraging workers of many basicerotines are often encrusted with a firmly bonded layer of soil, which is thought to function as camouflage, enhancing crypsis (Hölldobler & Wilson, 1986).

Knowledge of the basic natural history of these ants has hardly progressed since the observations of Wilson, Brown, and Hölldobler. More specimens are now available for examination due to quantitative litter sampling, enhancing knowledge of basicerotine diversity and distribution, but discovering nests remains exceedingly difficult. Quantitative samples of 1 m2 litter plots reveals that small basicerotines can be very frequent, occurring in over 50% of samples in some cases, but never in large numbers. Individual samples usually contain fewer than ten workers, and workers are often accompanied by dealate queens. These results suggest that colonies, at least among New World species, are usually small, with tens of workers.

Less than half of the species of Octostruma have their queens described. Ergatoid queens are known from some species. Males are known from collections for some species but none have been described. The mating biology of these ants and how common ergatoid queens are across the genus and within colonies is not known.

Castes

Worker

Nomenclature

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

  • iheringi. Rhopalothrix iheringi Emery, 1888c: 361 (q.) BRAZIL. Combination in Octostruma: Brown, 1949f: 92. Senior synonym of godmani, simoni, spei, wighti and material of the unavailable name sulcata referred here: Brown & Kempf, 1960: 187.
  • simoni. Rhopalothrix simoni Emery, 1890a: 67 (w.) VENEZUELA. Combination in R. (Octostruma): Forel, 1912e: 196; in Octostruma: Brown, 1949f: 92. Junior synonym of iheringi: Brown & Kempf, 1960: 187.
  • godmani. Rhopalothrix godmani Forel, 1899c: 41, pl. 3, fig. 4 (q.) PANAMA. Combination in Octostruma: Brown, 1949f: 92. Junior synonym of iheringi: Brown & Kempf, 1960: 187.
  • wighti. Rhopalothrix simoni var. wighti Wheeler, W.M. 1908b: 161 (w.) JAMAICA. Combination in Octostruma: Brown, 1949f: 92. Junior synonym of iheringi: Brown & Kempf, 1960: 187.
  • spei. Rhopalothrix (Octostruma) simoni r. spei Forel, 1912e: 196 (w.) COLOMBIA. Combination in Octostruma: Brown, 1949f: 92. Junior synonym of iheringi: Brown & Kempf, 1960: 187.

Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.

Description

Worker

Longino (2013) - HW 0.70–0.79, HL 0.63–0.73, WL 0.75–0.84, CI 106–111 (n=11). Labrum sides slightly concave, strap-like lateral portions converging from base to near apex, joined by thin translucent cuticle medially but leaving distinctly bilobed apex, with median notch; mandible triangular, in profile view with mandible closed, in same plane as clypeus, apex of mandible not strongly down-turned; with mandible fully open, dorsal face tilted obliquely relative to clypeus; mandible with 8 teeth, tooth 1 continuous with basal rim of dorsal surface, teeth 1–5 acute, tooth 1 smaller than tooth 2, teeth 2–5 similar in size, a minute denticle between 4 and 5, teeth 5–8 forming an apical fork, with 5 and 8 large, 6 and 7 small partially confluent denticles; dorsal surface of mandible roughened; ventral surface flat and parallel to clypeus apically, twisting basally to nearly perpendicular orientation basally, smooth and shining; interior surface concave, smooth and shining; scape flattened, with pronounced anterobasal lobe, dorsal surface faintly sculptured; clypeus with broad, shallow emargination anteriorly; clypeus shallowly punctate or punctatorugulose; face shallowly longitudinally rugulose with shiny surface, median ruga sometimes stronger than others; frontal carinae faint, nearly obsolete; antennal socket deep, dorsal rim of socket continuous with pronounced dorsal margin of antennal scrobe; antennal scrobe deep, strongly delimited dorsally, posteriorly, and ventrally with sharply defined, translucent foliaceous cuticular rim; compound eye small, circular, composed of about 5 ommatidia; distinct carina extends from ventral margin of antennal socket across floor of scrobe to compound eye; scrobe floor faintly foveolate anteroventrally, smooth and matte to feebly shining elsewhere; vertex margin anterior to occipital carina smooth (top of head, not visible in face view); occipital carina distinct, extending anteriorly on ventral surface of head to beyond level of compound eye but not reaching hypostoma; undersurface rugulose.

Promesonotum and dorsal face of propodeum form a continuous convexity in profile; promesonotal suture obsolete; promesonotum with shallow, longitudinal impression; metanotal groove obsolete to weakly impressed; propodeum with distinct dorsal and posterior faces; propodeal spines pronounced, in the form of acute translucent perpendicular plates, extending ventrally as broad foliaceous laminae; a single broad, translucent, transverse carina extends between propodeal spines, separating dorsal and posterior faces of propodeum; this carina broadens laterally and extends onto the propodeal spine, joining it at a right angle, forming an unusual roof-like structure over the posterior face of the propodeum and creating a thin-walled, concave propodeal spine that looks like a horse ear; propodeal spiracle large, located below propodeal spine and confluent with the ventral lamina, such that the translucent lamina can be seen as the back wall when looking through the spiracular orifice; all surfaces of mesosoma matte; dorsum of promesonotum irregularly rugose, dorsal and posterior faces of propodeum smooth, lateral pronotum faintly punctate; meso-metapleuron and side of propodeum confluent, smooth.

Petiole in profile with peduncle differentiated from node, node with distinct anterior face; node nearly triangular, with long sloping dorsal face and short vertical posterior face, dorsal and posterior faces separated by a distinct transverse carina; anteroventral margin with pronounced, anteriorly-directed peg-like tooth; postpetiole low, broad, crescent-shaped in dorsal view; dorsum of petiolar node rugose; dorsum of postpetiole faintly rugulose anteriorly, grading to punctate posteriorly; first gastral tergite and sternite uniformly punctate, interspaces subequal in width to puncta, smooth and shining.

Anterior labral lobe with radiating tuft of soft, thick, translucent, capitate setae of unequal length projecting from apex; each larger mandibular tooth with fully appressed seta running length of tooth; anterior margin of scape with about 10 spatulate setae; clypeus and face with fine, sparse fully appressed ground pilosity; face typically with eight erect spatulate setae arranged as in; setae on vertex margin arising from large, ringed puncta; mesosomal dorsum lacking erect setae; mesotibia with conspicuous subdecumbent clavate ground pilosity, about 2 larger spatulate seta at apex; petiole with 2 erect setae (rarely absent); postpetiole lacking erect setae; first gastral tergite lacking spatulate setae, ground pilosity fully appressed, sparse (length of setae less than distance between them); first gastral sternite with abundant short clavate setae over most of surface; pair of distinctive, long, extremely fine setae extending perpendicularly from petiolar peduncle, anterior to spiracle; similar but shorter pair of setae extending from sides of postpetiole, a few similar fine setae on anterior first gastral sternite, a short clavate seta extending posteriorly from posterior margin of hind coxa.

Color orange red.

Queen

Longino (2013) - HW 0.84, HL 0.71, WL 0.99, CI 119 (n=1). Labrum, mandible, scape, antennal scrobe, and head sculpture similar to worker; face with 8 erect setae distributed as in worker; ocelli distinct; compound eye large, multifaceted, about 12 ommatidia in longest row.

Mesosoma with queen-typical alar sclerites; pronotum irregularly rugose anteriorly, punctatorugose laterally; mesoscutum longitudinally rugose; axilla and scutellum irregularly rugose; scutellum with median impression; anepisternum and katepisternum separated by strong sulcus; anepisternum, katepisternum, and side of propodeum matte, mostly smooth with variable faint rugulae; propodeum and propodeal spines similar to worker, but dorsal face of propodeum much shorter than posterior face; pronotum with 2 erect setae, mesoscutum with about 6, axilla with 1, scutellum with 2, metanotum with 2, petiolar node with 2, postpetiolar disc with 0, first gastral tergite with 4. Other characters similar to worker.

Type Material

Holotype queen: Brazil, Rio Grande do Sul Museo Civico di Storia Naturale, Genoa (not examined).

References

  • Brown, W. L., Jr. 1949h. Revision of the ant tribe Dacetini: IV. Some genera properly excluded from the Dacetini, with the establishment of the Basicerotini new tribe. Trans. Am. Entomol. Soc. 75: 83-96 (page 92, Combination in Octostruma)
  • Brown, W. L., Jr.; Kempf, W. W. 1960. A world revision of the ant tribe Basicerotini. Stud. Entomol. (n.s.) 3: 161-250 (page 187, Senior synonym of godmani, simoni, spei and wighti, and material of the unavailable name sulcata referred here)
  • Emery, C. 1888c [1887]. Formiche della provincia di Rio Grande do Sûl nel Brasile, raccolte dal dott. Hermann von Ihering. Bull. Soc. Entomol. Ital. 19: 352-366 (page 361, queen described)
  • Longino, J.T. 2013. A revision of the ant genus Octostruma Forel 1912 (Hymenoptera, Formicidae). Zootaxa 3699, 1-61. doi:10.11646/zootaxa.3699.1.1