Ponera loi

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Ponera loi
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Ponerinae
Tribe: Ponerini
Genus: Ponera
Species: P. loi
Binomial name
Ponera loi
Taylor, 1967

Ponera loi is known only from forested areas near Afiamalu. According to Zimmerman (pers. comm.), his specimens were taken in undisturbed forest, at roadsides or along native trails. The Taylor and Ettershank material is from the disturbed forest. P. loi is evidently a rather rare species and appears, from the Taylor and Ettershank collections, to be much less abundant at Afiamalu than the similar and sympatric Ponera woodwardi. In intensive collecting there I took it only once, although it may have been overlooked at times, due to my confusing it with the common woodwardi, which was not always collected. (Taylor 1967)

Identification

Taylor (1967) - Similar to the New Guinean Ponera syscena, particularly in having a relatively narrow petiole node (petiolar node index 78-82). This character allows immediate separation of syscena and loi from the other members of the japonica species group, whose PNI's range from 84-91.

Workers of P. loi are easily distinguished from the sympatric Ponera woodwardi by differences in scape index (84-91 in loi, 98-102 in woodwardi). The other sympatric species on Samoa (Ponera incerta, Ponera swezeyi and Ponera tenuis) are all considerably smaller.

Keys including this Species

Distribution

Known only from the Samoan island of Upolu.

Distribution based on Regional Taxon Lists

Indo-Australian Region: Guam, Marshall Islands, Northern Mariana Islands, Samoa (type locality).

Distribution based on AntMaps

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Distribution based on AntWeb specimens

Check data from AntWeb

Biology

Little is known about the biology of Ponera loi.

The general biology of species in the genus was summarized by Taylor (1967): Ponera are small ants that nest in rotting logs in forested areas or under stones in nonforested situations. In the tropical areas specimens are rarely encountered away from rain forest. In temperate areas, however, species may occur in relatively lightly forested areas. This appears to be the case with Ponera japonica, Ponera pennsylvanica and especially with Ponera coarctata. The Australian Ponera leae is essentially limited to rain forest in the northern parts of its range, but further south it may be found in dry, lightly forested areas.

Foraging is probably cryptobiotic, though some New Guinea species have been taken straying on the ground surface. Little information is available concerning feeding. However, most species are probably insectivorous. I have conducted feeding experiments with some of the New Guinea and Samoan species, including Ponera xenagos, Ponera elegantula, Ponera tenuis, Ponera incerta and Ponera woodwardi. These were unsuccessful with the larger species, except elegantula, which accepted moderately large (8-12 mm) campodeid and japygid Diplura. Tenuis and incerta accepted smaller (4-6 mm) campodeids, isotomid and sminthurid Collembola, and small newly hatched spiders (2 mm long). Negative feeding response was obtained with eggs and larvae of various ants, small crushed insects of various orders, and small myriapods. Stray workers were never observed carrying prey, and distinct middens of insect or other remains were not located near nests.

Colonies usually contain about 30 workers. Larvae and pupae are not segregated in most cases, but occasionally aggregations of pupae were observed. These may have included the total brood of the colonies involved. Larvae are attached to the floor or walls of the nest galleries by the glutinous abdominal tubercles described above, and the ants move them high up on the walls or ceilings of artificial nests, if they are flooded. Details of nuptial behavior of pennsylvanica were given by Wheeler (1900), and Haskins & Enzmann (1938). The flights appear to be of a pattern typical for ants, with the alates meeting in the air and mating there or on the ground. Colony foundation is non-claustral and independent in pennsylvanica (Kannowski 1959); judging from my observations this is typical for the genus.

Castes

Nomenclature

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

  • loi. Ponera loi Taylor, 1967a: 60, figs. 52-55 (w.q.) SAMOA.

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

Description

Worker

Taylor 1967 Ponera fig 43-54

(Based on the holotype and 8 paratypes collected at Afiamalu by Zimmerman in 1940 and by Ettershank and me in 1962). Dimensions (holotype cited first): HL 0.66 mm, 0.62-0.70 mm; HW 0.53 mm, 0.51-0.58 mm; SL 0.46 mm, 0.44-0.52 mm; CI 80, 79-83; SI 87, 84-91, PW 0.40 mm, 0.37-0.42 mm; PNL 0.21 mm, 0.20-0.23 mm; PH 0.41 mm, 0.39-0.44 mm; DPW 0.33 mm, 0.30-0.34 mm; PNI 82, 78-81. With the characters of the japonica species group. Close to Ponera syscena in the details of mandibular, clypeal, and antennal structure, and in color, sculpturation, pubescence and pilosity. The loi types differ from the available syscena material in the following characters:

1. Head length 0.62-0.70 mm as opposed to 0.60-0.62 mm in syscena. The frequency distribution of HL measurements in loi is strongly skewed toward the high values. The mean HL values of the 2 species are: loi 0.66 mm (N=9); syscena 0.61 mm (N=7).

2. Head width 0.51-0.58 mm, opposed to 0.48-0.51 mm in syscena. The mean values again give more conclusive separation-in loi the mean HW is 0.54 mm (N=9); in syscena it is 0.49 mm (N=7).

3. The head of P. loi is proportionately larger relative to the body than that of syscena. In the former the head width ranges from 1.31 to 1.38 x the pronotal width, while in the latter, values of 1.23-1.28 X are yielded.

4. Median clypeal denticle distinctly developed in loi, vestigial in syscena.

5. The outline of the mesosomal dorsum in loi (fig. 53) is slightly indented at the mesometanotal suture, where it is straight and uninterrupted in syscena. The mesometanotal suture of loi, unlike that of syscena, is represented by a fairly marked transverse impression, which is accompanied by a fine and indistinct incised sutural trace in some specimens.

Queen

3 dealate paratypes collected by Swezey and Zimmerman in 1940 have the following dimensions: HL 0.71-0.73 mm; HW 0.60-0.63 mm; SL 0.50-0.55 mm; CI 85-86; SI 83-87; PW 0.50-0.53 mm; PNL 0.21-0.23 mm; PH 0.46-0.50 mm; DPW 0.38-0.40 mm; PNI 75-76; maximum diameter of eye 0.20; ocular index 32-33. Conforming to the general plan of queen structure for the genus, and differing from the workers in the usual characters of full sexuality. Medium clypeal denticle distinctly developed, as in the worker, and the apices of the scapes are almost exactly contiguous with the median occipital border.

Females of loi are distinguished from related species by the same characters differentiating the workers. The unique known Ponera colaensis queen is smaller, with a proportionately wide petiolar node (HW 0.54 mm; PNI 82), and woodwardi queens have narrower heads and longer scapes (CI 80-84; SI 99-102).

Type Material

Holotype and paratypes (worker and queen) in Museum of Comparative Zoology collection. Paratypes in Bernice P. Bishop Museum, The Natural History Museum, Australian National Insect Collection, Forel Coll. and National Museum of Natural History.

References