Pseudomyrmex penetrator

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Pseudomyrmex penetrator
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Pseudomyrmecinae
Genus: Pseudomyrmex
Species: P. penetrator
Binomial name
Pseudomyrmex penetrator
(Smith, F., 1877)

Pseudomyrmex penetrator casent0902883 p 1 high.jpg

Pseudomyrmex penetrator casent0902883 d 1 high.jpg

Specimen Labels

Synonyms

P. penetrator is associated with Tachigali, making its nests within and foraging upon plants of this genus.

Identification

Distribution

Widely distributed in the east/central Amazon basin and adjacent Guianas.

Distribution based on Regional Taxon Lists

Neotropical Region: Brazil (type locality), Guyana, Suriname, Venezuela.

Distribution based on AntMaps

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Distribution based on AntWeb specimens

Check data from AntWeb

Biology

Fonseca (1993) provides information on the biology of this ant (under the name P. nigrescens).

Castes

Nomenclature

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

  • penetrator. Pseudomyrma penetrator Smith, F. 1877b: 66 (q.) BRAZIL. Combination in Pseudomyrmex: Kempf, 1958: 435. Junior synonym of concolor: Kempf, 1967c: 5. Revived from synonymy and senior synonym of coronata Wheeler (and its junior synonym coronata Enzmann), nigrescens: Ward, 1999b: 499.
  • nigrescens. Pseudomyrma latinoda var. nigrescens Forel, 1904c: 38 (w.) BRAZIL. Combination in Pseudomyrmex: Kempf, 1961a: 400. Raised to species: Ward, 1990: 485. Junior synonym of penetrator: Ward, 1999b: 500.
  • coronata. Pseudomyrma latinoda var. coronata Wheeler, W.M. 1942: 167 (w.m.) GUYANA. Combination in Pseudomyrmex: Kempf, 1961a: 400. Senior synonym of coronata Enzmann: Brown, 1949a: 42. Subspecies of concolor: Ward, 1989: 436. Raised to species: Ward, 1990: 484. Junior synonym of penetrator: Ward, 1999b: 500.
  • coronata. Pseudomyrma latinoda var. coronata Enzmann, E.V. 1944: 88 (w.) GUYANA. [Unresolved junior primary homonym of coronata Wheeler, above.] Junior synonym of coronata Wheeler: Brown, 1949a: 42.

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

Ward (1999) - This is a ‘dark form’ very closely related to, and possibly conspecific with, Pseudomyrmex concolor. The circumstances are complicated. In a number of localities the two color forms occur sympatrically and appear to retain their distinctness. Studies in the Manaus region even indicate that the two morphs are ecological differentiated, with P. penetrator (= P. nigrescens) occupying older Tachigali plants than P. concolor and achieving larger colony sizes (Fonseca, 1993). Yet elsewhere, the morphological distinctions are blurred, and one collection from 100 km E Humaita in southeastern Amazonas (leg. F. Rickson) contains both dark and light workers within a single nest series. The queen of this nest series is mostly dark brown, but has a contrastingly light head and patches of orange-brown coloration on the pronotum, mesoscutum, and anepisternum. There are also morphologically intermediate individuals in collections made by Benson, Brandao, and others in the Serra do Carajas, Para. In the Carajas samples some workers and queens appear to be typical dark-bodied P. penetrator, but others are more problematic: these have a lighter orange-brown coloration on all or parts of the mesosoma, petiole and postpetiole, and in a few workers the light coloration even extends to the fourth abdominal (first gastric) segment. Finally, the colour differences between the type queens of P. penetrator and P. concolor, both from Sao Paulo de Olivenca in western Amazonia, are less pronounced than in populations from eastern Amazonia and the Guianas, although this might be due to a loss of colour difference with time.

Similar patterns of colour variation, involving light- and dark-coloured individuals, occur in the related species Pseudomyrmex insuavis and Pseudomyrmex malignus, but in those cases the variation is clearly intraspecific. The situation in P. concolor/P. penetrator is more intriguing, and suggests reproductive isolation between the forms in some regions but not others. Besides the breakdown in colour as a diagnostic character in peripheral (southeastern) populations, another observation indicating gene flow between populations of P. concolor and P. penetrator is the occurrence of concordant geographical variation in morphology. For example, the type queens of P. concolor and P. penetrator, from the same locality in western Amazonia, are both exceptionally large (HW 1.39) with elongate heads (CI 0.79). Conversely, queens of P. concolor and P. penetrator from Guyana and Venezuela tend to have broader (CI 0.84–0.87) and less shiny heads (owing to the greater development of fine striolate-reticulate sculpture on the frons) than their eastern Amazonian counterparts (CI 0.79–0.86). Of course, an alternative explanation for such concordant variation is similar selection pressures on queen morphology in two sibling species. The situation calls for a detailed genetic analysis. I could find no consistent differences between P. concolor and P. penetrator in the form of the male genitalia, and this contrasts with the typical situation in the viduus group in which the male genitalia provide species-diagnostic characters.

Description

Worker

Ward (1999) - Measurements (n=24). HL 0.97–1.23, HW 0.89–1.13, MFC 0.093–0.136, LHT 0.70–0.93, CI 0.86–0.97, REL 0.36–0.42, REL2 0.38–0.44, FCI 0.09–0.13, SI 0.39–0.43, FLI 0.97–1.44, FI 0.39–0.46, PLI 0.77–0.92, PWI 0.75–0.89, PPWI 1.48–1.82.

Very similar to Pseudomyrmex concolor (q.v.) in size, shape, sculpture and pilosity (MSC 28–53; HTC 8–16), differing primarily in colour. Gaster, and usually also mesosoma, petiole and postpetiole, dark brown; head concolorous brown or a contrasting orange-brown, with variable amounts of infuscation (especially around the ocellar triangle). Antennae, tarsi and (sometimes) tibiae lighter yellow-brown. Petiole tending to be perhaps lower (compare PLI values), with a smaller subpetiolar process, and postpetiole tending to be broader (compare PPWI values), but these differences, if real, are slight and not diagnostic.

Type Material

Ward (1999):

Syntype alate queen, “St. Paul” [Sao Paulo de Olivenca], Amazonas, Brazil (The Natural History Museum) [Examined].

Pseudomyrma latinoda var. nigrescens Forel, 1904a:38. Syntype workers, Para, Brazil (Goldi) (Museum of Comparative Zoology, Musee d'Histoire Naturelle Genève) [Examined].

Pseudomyrma latinoda var. coronata Wheeler, 1942:167. Syntype workers, Kamakusa, Guyana (H. O. Lang) (MCZC) [Examined]. One worker here designated as Lectotype.

Pseudomyrma latinoda var. coronata Enzmann, 1944:88. Syntype workers, Mouth of Merume, Guyana (H. O. Lang) (MCZC) [Examined]. One worker here designated as Lectotype.

References

  • Kempf, W. W. 1958f. Estudos sôbre Pseudomyrmex. II. (Hymenoptera: Formicidae). Stud. Entomol. (n.s.) 1: 433-462 (page 435, Combination in Pseudomyrmex)
  • Kempf, W. W. 1967c. Estudos sôbre Pseudomyrmex. IV (Hymenoptera: Formicidae). Rev. Bras. Entomol. 12: 1-12 (page 5, Junior synonym of concolor)
  • Smith, F. 1877b. Descriptions of new species of the genera Pseudomyrma and Tetraponera, belonging to the family Myrmicidae. Trans. Entomol. Soc. Lond. 1877: 57-72 (page 66, queen described)
  • Ward, P. S. 1999b. Systematics, biogeography and host plant associations of the Pseudomyrmex viduus group (Hymenoptera: Formicidae), Triplaris- and Tachigali-inhabiting ants. Zool. J. Linn. Soc. 126: 451-540 (page 499, Revived from synonymy and senior synonym of coronata Wheeler (and its junior synonym coronata Enzmann) and nigrescens)