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Species: Leptanilla palauensis   (Smith, 1953) 

Classification:
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Taxonomic History (provided by Barry Bolton, 2019)

Probolomyrmex palauensis Smith, 1953c PDF: 128, figs. 1, 2 (m.) PALAU IS. Oceania. AntCat AntWiki HOL

Taxonomic history

Combination in Leptanilla: Taylor, 1965d PDF: 363.
See also: Petersen, 1968 PDF: 596.

Distribution:

  Geographic regions (According to curated Geolocale/Taxon lists):
    Oceania: Micronesia, Palau
  Biogeographic regions (According to curated Bioregion/Taxon lists):
    Oceania

Taxonomic Treatment (provided by Plazi)

Treatment Citation: Taylor, R. W., 1965, A monographic revision of the rare tropicopolitan ant genus Probolomyrmex Mayr (Hymenoptera: Formicidae)., Transactions of the Royal Entomological Society of London 117, pp. 345-365

VI. A Species Properly Excluded from ProbolomyrmexHNS: (?) Leptanilla palauensis (M. R. Smith)HNS, comb. n.

Probolomyrmex palauensis M. R. SmithHNS, 1953, J. N. Y. ent. Soc. 61: 127 - 129, figs. 1 - 2. [[ male ]]. Type locality: S. W. of Ulimang, Babelthaup I., Palau Islands, Micronesia. Holotype: United States National Museum (examined).

This species was described from a single male collected without associated workers or queens. The general habitus is somewhat like that of the female castes of ProbolomyrmexHNS, but knowledge of the male of P. greavesiHNS precludes the possibility that palauensisHNS belongs in that genus.

A completely satisfactory generic assignment for palauensisis not possible at present. Inclusion in the Formicidae is acceptable on the basis of the nodal form and other general characters, although metapleural glands are not visible on the specimen. The presence of these organs is apparently a universal and definitive character in female ants, but their presence among the males has never been objectively surveyed. A spot check in the Museum of Comparative Zoology collection shows that metapleural glands are lacking, or externally indiscernible, in the males of many genera. Placement in the subfamily PonerinaeHNS is not tenable, since all known ponerine ants, of all castes, have the tergum and sternum of the second post-petiolar (fourth true abdominal) segment fused laterally to form a strong tubular structure and this is not so in the holotype of palauensisHNS.

I have concluded that a queried assignment to the genus LeptanillaHNS (subfamily LeptanillinaeHNS) provides the best placement for palauensisHNS. A number of male-based species have been described in LeptanillaHNS or in the possibly synonymous genus PhaulomyrmaHNS by Santschi (1907, 1908) and by G. C. & E. W. Wheeler (1930). However, none of the known leptanilline males were collected in definite association with workers, and until such specimens are available the status of the Wheeler and Santschi species must be questioned. The only presumed leptanilline male available here for comparison with palauensisHNS is the holotype of Phaulomyrma javana WheelerHNS and Wheeler. The two specimens agree sufficiently well for relationship between them to be reasonably assumed: if PhaulomyrmaHNS is truly a leptanilline ant, then palauensisHNS probably is also.

The holotype of palauensisHNS resembles the presumed Leptanilla-Phaulomyrma males in the following features:

(1) The structure of the head, mandibles, frontoclypeal region, antennae, eyes and ocelJi. The oral palpi are unfortunately not visible in palauensisHNS.

(2) The torn wing fragments appear to have had extremely reduced venation, as in the leptanillines.

(3) The presence of one apical spur on the middle tibia and two on the posterior one, a feature characteristic of several of the described " LeptanillaHNS " males.

(4) Fusion of the lateral mesosomal sclerites is more marked in palauensisHNS than in the leptanillines, but the form of this tagma and of the petiole and gaster, is similar.

(5) The apparent absence of metapleural glands, which are not visible in the slidemounted type of PhaulomyrmaHNS, even under phase-contrast examination.

(6) Workers and queens of available LeptanillaHNS species do not have the sclerites of the fourth abdominal segment fused laterally. This is so in the PhaulomyrmaHNS male, and apparently also in the described LeptanillaHNS males, as well as in the type of palauensisHNS.

(7) The peculiar structure of the terminalia, especially that of the much enlarged non-retractile genital capsule, with its greatly elongated aedeagus. Wheeler & Wheeler (1930: fig. 2 c) show a ventral view of the genital capsule of PhaulomyrmaHNS. In the specimen illustrated the apices of the gonoforceps are folded inwards in an apparently unnatural position; if they were unfolded the genital apex would closely resemble that of palauensisHNS, as shown in Smith's figure 2. A similar folding of the gonoforceps evidently occurred in the specimens illustrated by Santschi, and with appropriate correction they too would resemble palauensisHNS.

According to the diagnoses of Wheeler & Wheeler (1930), palauensisHNS appears closer to PhaulomyrmaHNS in some features than to LeptanillaHNS. However, placement of this species in LeptanillaHNS seems sensible in view of the uncertainty surrounding the status of all these forms.



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