Crematogaster grevei

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Crematogaster grevei
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Crematogastrini
Genus: Crematogaster
Species: C. grevei
Binomial name
Crematogaster grevei
Forel, 1891

Crematogaster grevei casent0101558 profile 1.jpg Crematogaster grevei casent0101558 dorsal 1.jpg Specimen labels

Fisher et al. frequently collected this species nesting in dead twigs on and above the ground, in rotten logs, from leaf litter samples, and also found it occasionally nesting under stones or in stems of live plants. The two colour variants of C.grevei have nearly allopatric distributions. The nature of these distributions suggests that the orange variant is associated with the spiny forests of the far south and southwest parts of Madagascar, while the brown or black variant is adapted to western dry and western subhumid forest habitats. Very likely some environmental variables play a role in stabilizing this colour dimorphism, at the moment however too little is known about the ecology of the species to make further assumptions. (Blaimer 2010)

Identification

Crematogaster grevei is recognizable by a combination of the following characters. The lateral portions of the promesonotum are raised with respect to the median portion and end in postero-lateral carinate denticles. Lateral carinae border the metanotal groove. The petiole has postero-lateral tubercles dorsally that each bear a single, stiff and long erect seta; the postpetiole is distinctly bilobed and broadly medially impressed, and also bears a pair of dorso-posterior stiff, long erect setae. Further noteworthy are the short and straight spines, the erect pilosity on abdominal tergites 4–7, and the mandibles that possess only 4 teeth. (Blaimer 2010)

Keys including this Species

Distribution

Crematogaster grevei occurs throughout the seasonally dry forests and spiny forests of western and southwestern Madagascar. Among

Distribution based on Regional Taxon Lists

Malagasy Region: Madagascar (type locality).


Distribution based on AntMaps

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Distribution based on AntWeb specimens

Check data from AntWeb

Biology

Castes

Apart from colouration, the two variants of C.grevei exhibit slight variations in head sculpture. Some size polymorphism is exhibited in the workers of this species. Larger workers that have a disproportionately larger mesosoma than head are often found among colony samples of normal-sized workers. (Blaimer 2010)

Worker

Nomenclature

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

  • grevei. Crematogaster grevei Forel, 1891b: 183, pl. 6, fig. 8 (w.) MADAGASCAR. Blaimer, 2010: 16 (q.). Combination in C. (Decacrema): Forel, 1910a: 18; Forel, 1910f: 9. See also: Blaimer, 2010: 14.

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

Description

Worker

Blaimer (2010) - Measurements (n=12). HW 0.82–0.89; HL 0.72–0.78; EL 0.16–0.21; SL 0.66–0.74; WL 0.79– 1.07; SPL 0.13–0.18; PTH 0.18–0.22; PTL 0.24–0.29; PTW 0.26–0.31; PPL 0.15–0.20; PPW 0.27–0.32; LHT 0.57–0.63; CI 1.11–1.18; OI 0.21–0.27; SI 0.92–0.98; SPI 0.13–0.22; PTHI 0.74–0.79; PTWI 1.01–1.20; PPI 1.43–1.84; LBI 1.29–1.71.

Small species (HW 0.82–0.89, WL 0.79–1.07).

Masticatory margin of mandibles with 4 teeth; posterior margin of head in full-face view with subangular corners, sometimes medially depressed; antennal scapes surpassing posterior margin of head easily; midline of eyes situated well above midline of head in full face view.

Promesonotum medially depressed and laterally with raised shoulders, these transitioning into lateral carinae and terminating in small denticles that abruptly demarcate promesonotum from propodeum; in lateral view outline of promesonotum flat; promesonotal suture absent; promesonotum without a distinct posterior face medially; propodeal spines small-medium sized (SPI 0.13–0.22), length roughly a third of the width between their bases, quickly tapering, in lateral view more or less straight, in dorsal view almost parallel and barely diverging; petiole in dorsal view suboval, with dorso-lateral margins carinate, terminating in small postero-lateral tubercules; subpetiolar process developed as broad, rounded protuberance; postpetiole distinctly bilobed and broadly medially impressed.

Head sculpture reduced aciculate to aciculate-reticulate, more pronounced in darker coloured form than in orange-red variety; mesosoma with promesonotum dorsally irregularly carinulate-reticulate; meso- and metapleuron carinulate-areolate; propodeum with dorsal face carinulate and first half of posterior face reticulate, otherwise shiny; legs shiny to reticulate; dorsal face of petiole mostly reticulate, centrally shiny; postpetiole dorsally feebly reticulate; lateral and ventral face of petiole and postpetiole coarsely reticulate; helcium dorsally shiny or reticulate, at most feebly carinulate; promesonotum with 4-8 erect humeral setae, rarely with 2 additional setae on lateral carinae; petiole with single stiff, long erect setae on each postero-lateral tubercle; postpetiole with a pair of erect dorso-posterior setae; abdominal tergites 4–7 with scattered erect pilosity.

Two distinct colour variants: first variant distinctly bi-coloured, with pale to bright orange-red head, mesosoma, legs, petiole and postpetiole that contrast with a brown to almost black gaster; second variant (to which the lectotype belongs) uni-coloured, from reddish brown to brown to dark brown, to entirely black.

Queen

Blaimer (2010) - Measurements (n=3). HW 1.26–1.33, HL 1.06–1.15, EL 0.36–0.39, SL 0.87–0.93, MSNW 0.92–1.05, MSNL 1.71–1.93, PTH 0.31–0.36, PTL 0.41–0.42, PTW 0.48–0.53, PPL 0.30–0.34, PPW 0.46–0.53, SPL 0.03–0.08, WL 2.06–2.23, LHT 0.88–0.96, CI 1.11–1.26, OI 0.32–0.37, SI 0.76–0.83, MSNI 0.51–0.55, PTHI 0.74–0.87, PTWI 1.15–1.28, PPI 1.54–1.58, SPI 0.01–0.04, LBI 2.33–2.38.

Small (HW 1.26–1.33, WL 2.06–2.23). With worker characters, except as follows. Antennal scapes just barely surpassing posterior margin of head; eyes situated at midline of head in full face view; posterior margin of head straight.

Mesosoma slender (MSNI 0.51–0.55, WL 2.06–2.23); mesoscutum in dorsal view oval, about half as wide as long; mesopleuron with episternal groove carinulate to broadly carinate; in lateral view mesepisternum meeting pronotum at an oblique angle; postscutellum with posterior face rounded to flattened; propodeal suture deep and laterally reaching until level of propodeal spiracle; dorsal face of propodeum short, about one third of the size of posterior face; propodeal spines reduced, ranging from tubercule to denticles to very sharp points; petiole and postpetiole as in worker, but less prominently shaped and dorso-posterior tubercule on petiole lacking; antero-ventral subpetiolar tooth present, but reduced with respect to worker.

Propodeum with vertical carinulae on dorsal and posterior face; petiole reticulate throughout; postpetiole feebly reticulate throughout; face with 10–12 erect setae and abundant appressed pilosity; mesonotum with 20–26 erect setae; petiole and postpetiole with dorso-posterior setae and further with appressed pilosity throughout.

Colour brown to dark brown, or orange-red with gaster dark brown or black.

Type Material

Blaimer (2010) - Syntypes, 2 workers, Morondava (Greve) (Musee d'Histoire Naturelle Genève) [examined] [CASENT0101572, CASENT0101558]. One syntype (CASENT0101572) hereby designated lectotype. One of the MHNG syntypes carries matching locality data and collector information with the type description and is hence chosen as the lectotype.

References

  • Bonnie B. Blaimer 2010. Taxonomy and Natural History of the Crematogaster (Decacrema)-group (Hymenoptera: Formicidae) in Madagascar. Zootaxa. 2714:1–39. PDF
  • Forel, A. 1891c. Les Formicides. [part]. In: Grandidier, A. Histoire physique, naturelle, et politique de Madagascar. Volume XX. Histoire naturelle des Hyménoptères. Deuxième partie (28e fascicule). Paris: Hachette et Cie, v + 237 pp. (page 183, pl. 6, fig. 8 worker described)
  • Forel, A. 1910a. Glanures myrmécologiques. Ann. Soc. Entomol. Belg. 54: 6-32 (page 18, Combination in C. (Decacrema))
  • Forel, A. 1910e. Zoologische und anthropologische Ergebnisse einer Forschungsreise im westlichen und zentralen Südafrika ausgeführt in den Jahren 1903-1905 von Dr. Leonhard Schultze. Vierter Band. Systematik und Tiergeographie. D) Formicidae. Denkschr. M (page 9, Combination in C. (Decacrema))
  • Wheeler, W. M. 1922k. Ants of the American Museum Congo expedition. A contribution to the myrmecology of Africa. IX. A synonymic list of the ants of the Malagasy region. Bull. Am. Mus. Nat. Hist. 4 45: 1005-1055 (see also)