Octostruma lutzi

Octostruma lutzi
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Hymenoptera
Family:	Formicidae
Subfamily:	Myrmicinae
Tribe:	Attini
Genus:	Octostruma
Species:	O. lutzi
Binomial name
Octostruma lutzi (Wheeler, W.M., 1913) Specimen Label

Octostruma lutzi is an island species endemic to Dominica and Guadeloupe in the Lesser Antilles. The syntypes were collected "sifting leaves in forest and among bananas and tree-ferns along the edge of it." (Wheeler, 1913). On Guadeloupe, it occurs from sea level to 800 m elevation, in a variety of forested habitats including wet and seasonal dry forest, mahogany plantation, and cloud forest. All Guadeloupe specimens are from Winkler samples of sifted litter and rotten wood from the forest floor. Dealate queens often occur together with workers in litter samples. (Longino 2013)

Identification

Keys including this Species

• Key to Octostruma species

Distribution

Distribution based on Regional Taxon Lists

Neotropical Region: Dominica (type locality), Guadeloupe, Montserrat.

Distribution based on AntMaps

Distribution based on AntWeb specimens

Check data from AntWeb

Countries Occupied

Number of countries occupied by this species based on AntWiki Regional Taxon Lists. In general, fewer countries occupied indicates a narrower range, while more countries indicates a more widespread species.

Estimated Abundance

Relative abundance based on number of AntMaps records per species (this species within the purple bar). Fewer records (to the left) indicates a less abundant/encountered species while more records (to the right) indicates more abundant/encountered species.

Biology

Explore Overview of Octostruma 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. ‎

Nomenclature

The following information is derived from Barry Bolton's Online Catalogue of the Ants of the World.

• lutzi. Rhopalothrix (Octostruma) lutzi Wheeler, W.M. 1913d: 241 (w.q.) DOMINICA. Combination in Octostruma: Brown, 1949f: 92. Junior synonym of balzani: Brown & Kempf, 1960: 194. Revived from synonymy: Longino, 2013: 41.

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

Longino (2013) - The original syntype series of O. lutzi contained both O. lutzi (one of which was designated lectotype in Brown and Kempf, 1960) and Eurhopalothrix guadeloupensis. Wheeler's description of O. lutzi pertains to O. lutzi for the most part, but the description of pilosity better fits the Eurhopalothrix worker. The identity of the described queen remains uncertain.

The degree to which the Dominica and Guadeloupe populations are differentiated is poorly known. Examined workers from Dominica (the MCZ type series of O. lutzi) have distinctly narrower heads than workers from Guadeloupe (CI 102–104 vs. 107–109). The Dominica workers are light orange brown and the Guadeloupe workers are dark brown, but the former are also over 100 years old and may have faded.

Description

Worker

Longino (2013) - Dominica: HW 0.56–0.61, HL 0.55–0.59, WL 0.61–0.64, CI 102–104 (n=3). Guadeloupe: HW 0.57–0.62, HL 0.53–0.58, WL 0.60–0.65, CI 107–109 (n=6). Mesosoma typically with two pairs spatulate setae, one on pronotum and one on mesonotum (pronotal setae lacking in all other balzani-group species except Octostruma batesi and Octostruma betschi); posterolateral margin of head subequal to or longer than anterolateral margin (posterolateral margin shorter than anterolateral margin in O. batesi and O. betschi); color dark brown on Guadeloupe.

Queen

Longino (2013) - The Dominica queen described by Wheeler was not examined. Guadeloupe queen: HW 0.65–0.66, HL 0.61–0.62, WL 0.77–0.80, CI 105–108 (n=3). Labrum, mandible, scape, antennal scrobe, and head sculpture similar to worker; face with 8–10 erect setae distributed symmetrically around lateral and posterior margins of head, a seta on low ridge in front of each compound eye, 4 setae across vertex between compound eyes; ocelli distinct; compound eye large, multifaceted, about 12 ommatidia in longest row.

Mesosoma with queen-typical alar sclerites; sculpture like workers; anepisternum and katepisternum separated by strong sulcus; posterodorsal propodeum concave; propodeal spines pronounced, in the form of flattened perpendicular plates, acute in profile; pronotum with 4 erect setae, mesoscutum with 10–12, axilla with 1, scutellum with 2, metanotum with 2, petiolar node with 4, postpetiolar disc with 4, first gastral tergite with about 40. Other characters similar to worker.

Snytype Specimen Labels

Type Material

Lectotype worker: Dominica, Laudet & Long Ditton, near Roseau (Lutz) Museum of Comparative Zoology, MCZ-ENT00303378 (examined); non-type queen: same data as lectotype AMNH? (not examined).

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
• Meurgey, F. 2020. Challenging the Wallacean shortfall: A total assessment of insect diversity on Guadeloupe (French West Indies), a checklist and bibliography. Insecta Mundi 786: 1–183.

References based on Global Ant Biodiversity Informatics

• Galkowski C. 2016. New data on the ants from the Guadeloupe (Hymenoptera, Formicidae). Bull. Soc. Linn. Bordeaux 151, 44(1): 25-36.
• Longino J. T. 2013. A revision of the ant genus Octostruma Forel 1912 (Hymenoptera, Formicidae). Zootaxa 3699(1): 1-61.
• Perrault G. H. 1988. Octostrumma [sic] betschi, n. sp. de Guyane Française (Hymenoptera, Formicidae). Revue Française d'Entomologie (Nouvelle Série) 10: 303-307.