Octostruma cyrtinotum

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Octostruma cyrtinotum
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Attini
Genus: Octostruma
Species: O. cyrtinotum
Binomial name
Octostruma cyrtinotum
Longino, 2013

Octostruma cyrtinotum P casent0615495.jpg

Octostruma cyrtinotum D casent0615495.jpg

Specimen Label

Octostruma cyrtinotum is a moderately abundant montane species in Honduras and Guatemala. All records are from 1300–1700 m. It occurs in mesophyll cloud forest, and montane forests with various mixtures of pine, oak, and Liquidambar. All collections are from Berlese and Winkler samples of sifted litter and rotten wood from the forest floor. In quantitative 1 m2 litter plot samples, it can occur in up to 28% of samples. Dealate queens are occasionally found together with workers in litter samples. (Longino 2013)

Identification

Longino (2013) - Face lacking transverse arcuate carina; basal five teeth of mandible acute; apex of labrum bilobed; face typically with 8 spatulate setae, seta-bearing pits along vertex margin large; filiform setae lacking on petiole, postpetiole, first gastral sternites; anterior half of dorsal face of propodeum convex, demarcating impressed metanotal groove; a single pair of spatulate setae on the mesonotum.

This species is very similar to the allopatric Octostruma montanis, from montane sites in southern Nicaragua and northern Costa Rica. The two differ only in small differences in the number of spatulate setae. The three species O. cyrtinotum, Octostruma montanis, and Octostruma planities possibly form a clade based on shared labral shape, similar size and shape, and orange coloration. Octostruma planities is a lowland species, showing an elevational parapatric distribution with both O. cyrtinotum and O. montanis.

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Neotropical Region: Honduras (type locality), Nicaragua.


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

Nomenclature

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

  • cyrtinotum. Octostruma cyrtinotum Longino, 2013: 28, figs. 1C, 3B, 5L, 13A, 14B, 22, 43 (w.) HONDURAS.

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

Description

Worker

HW 0.70–0.80, HL 0.65–0.74, WL 0.78–0.90, CI 107–112 (n=8). 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 deep median notch; mandible triangular, in profile view with mandible closed, in same plane as clypeus, apex of mandible not down-turned; with mandible fully open, dorsal face remains in same plane as clypeus; mandible with 8 teeth, tooth 1 continuous with basal rim of dorsal surface, teeth 1–5 acute, similar in shape, 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 shallowly rugulose; clypeus with broad, shallow emargination anteriorly; clypeus smooth and shiny with sparse shallow puncta; face shallowly irregularly rugulose with shiny surface; 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 thin cuticular rim; compound eye small, circular, composed of about 7 ommatidia; distinct carina extends from ventral margin of antennal socket across floor of scrobe to compound eye; scrobe floor smooth and shiny; vertex margin anterior to occipital carina smooth and shining (top of head, not visible in face view); occipital carina extends anteriorly on ventral surface of head nearly to hypostoma; postgenal suture visible as dark line on undersurface of head; undersurface rugulose.

Promesonotum moderately convex in profile, promesonotal suture moderately impressed, promesonotum with broad, weak, longitudinal impression; metanotal groove more strongly impressed, conspicuous in profile view; propodeum with distinct dorsal and posterior faces; dorsal face distinctly convex anteriorly, forming a gibbosity in profile view; propodeal spines well-developed, in the form of acute flattened perpendicular plates, extending ventrally as thin carinae; single well-defined transverse carina extends between propodeal spines, separating dorsal and posterior faces of propodeum; propodeal spiracle medium-size, diameter less than width of base of propodeal spine, located below propodeal spine and abutting posterior margin; all surfaces of mesosoma matte except posterior face of propodeum, which is shiny; dorsum of promesonotum irregularly rugose, dorsal face of propodeum faintly rugulose, posterior face of propodeum smooth, lateral pronotum punctate; meso- metapleuron and side of propodeum confluent, smooth.

Petiole in profile with peduncle differentiated from node, node with differentiated anterior face; node subquadrate, with long sloping dorsal face and short vertical posterior face; 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 densely punctate, tergal puncta fainter posteriorly but still extending to posterior border.

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 nine stiff spatulate setae; clypeus and face with fine, sparse fully appressed ground pilosity; face typically with eight erect spatulate setae; setae on vertex margin arising from large, ringed puncta; pronotum lacking erect setae (one pair on CASENT0610706, Honduras, Olancho: 11km NNE Catacamas); mesonotum typically with a pair of erect spatulate setae located at the juncture of pro- and mesonotum (lacking on CASENT0610830, Honduras, Francisco Morazán, 21km S Guaimaca); mesotibia with conspicuous ground pilosity, about 5 spatulate setae of variable length at apex; petiole and postpetiole lacking erect setae; first gastral tergite with 2–4 (typically 4) long spatulate setae at posterior margin, 3–8 setae on disc, ground pilosity fully appressed, sparse (length of setae less than distance between them); first gastral sternite with abundant spatulate setae clustered on posterior half, anterior half to one third devoid of setae, sternal setae shorter than tergal setae.

Color red brown.

Queen

HW 0.89–0.91, HL 0.78–0.81, WL 1.14–1.17, CI 111–115 (n=3). Labrum, mandible, scape, antennal scrobe, and head sculpture similar to worker; face with 8 erect setae distributed as in worker, plus 1–2 on central frons, anterior to lateral ocelli; 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 coarsely longitudinally rugose; axilla and scutellum coarsely irregularly rugose; 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; pronotum with about 4 erect setae, mesoscutum with about 6, axilla with 1, scutellum with 2, metanotum with 2, petiolar node with 2, postpetiolar disc with 2, first gastral tergite with about 20. Other characters similar to worker.

Type Material

Holotype Specimen Labels

Holotype worker: Honduras, Olancho: PN La Muralla, 15.09832, -86.74043, ±20 m, 1530 m, 2 May 2010, cloud forest, ex sifted leaf litter (LLAMA, Wa-C-01-1-06) California Academy of Sciences, unique specimen identifier CASENT0615495. Paratype workers: same data except 15.09734, -86.73912, , ±20 m, 1490 m (LLAMA, Wm-C-01-1-01) Museum of Comparative Zoology, CASENT0639167; National Museum of Natural History, CASENT0639168; University of California, Davis, CASENT0639169; Colección de Artrópodos, CASENT0639170; Escuela Agricola Panamericana, CASENT0639171; 15.09489, -86.73944, ±125 m, 1420 m (LLAMA, Wm-C-01-2-01) Colección Entomológica de El Colegio de la Frontera Sur, CASENT0627374; Museu de Zoologia da Universidade de Sao Paulo, CASENT0627375; John T. Longino Collection, CASENT0627376].

Etymology

The name refers to the convexity on the propodeal dorsum. It is a noun in apposition and thus invariant.

References

  • 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