Crematogaster sewellii is commonly found in high-altitude grassland, savannah and woodland habitat in the central and south-central highland region (800-1500 m), and at lower elevations (160-600 m) in the Makay massif and the RF Beanka in western Madagascar. The species often co-occurs with Crematogaster mafybe and Crematogaster degeeri, and otherwise with all other species of the C. degeeri-assemblage except Crematogaster malahelo. This species appears to nest exclusively on the ground, either in the soil or under stones. (Blaimer and Fisher 2013)
- 1 Identification
- 2 Distribution
- 3 Biology
- 4 Castes
- 5 Nomenclature
- 6 References
A member of the Crematogaster degeeri group. Blaimer and Fisher (2013) - Crematogaster sewellii can be identified with the following unique combination of characters: very large eyes (OI 0.24-0.29), antennal scapes usually long (SI 0.77-0.87) and surpassing head margin, propodeal spines reduced to small denticles, and distinct bicoloration with head and thorax yellowish to dark orange and metasoma with abdominal segments four to seven black.
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Distribution based on Regional Taxon Lists
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The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.
- sewellii. Crematogaster inermis r. sewellii Forel, 1891b: 196, pl. 6, fig. 9 (w.) MADAGASCAR. Combination in C. (Crematogaster): Wheeler, W.M. 1922a: 844; in C. (Acrocoelia): Emery, 1922e: 148; in C. (Crematogaster): Bolton, 1995b: 166. Raised to species: Dalla Torre, 1893: 86; Mayr, 1895: 138; Emery, 1895f: 342. Current subspecies: nominal plus acis, marnoi.
Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.
Blaimer and Fisher (2013):
(n = 20) HW 0.72-0.99; HL 0.66-0.89; EL 0.18-0.23; SL 0.56-0.70; WL 0.75-1.01; SPL 0.01-0.04; PTH 0.15-0.21; PTL 0.20-0.28; PTW 0.24-0.33; PPL 0.12-0.19; PPW 0.22-0.29; LHT 0.54-0.73; CI 1.08- 1.13; OI 0.24-0.29; SI 0.77-0.87; SPI 0. 01-0.05; PTHI 0.68-0.87; PTWI 1.07-1.32; PPI 1.54-1.92; LBI 1.30-1.45.
Masticatory margin of mandibles with four teeth; head shape fairly quadrate or slightly wider than long (CI 1.08-1.13); posterior margin of head in full-face view laterally subangular or rounded, often slightly medially depressed; occipital carinae distinct; antennal scapes usually reaching or surpassing head margin; midline of eyes situated distinctly above midline of head in full-face view; eyes large (OI 0.24-0.29) and strongly protruding. Pronotum laterally angular; promesonotal suture indistinct; mesonotum usually forming a flat plane with respect to pronotum; mesonotum usually with a short posterior face; mesonotum angular laterally, posterior face carinate, distinctly set off from propodeum; posterior face of mesonotum sloping steeply into metanotal groove; metanotal groove fairly shallow, laterally constricted and bordered by carinae; propodeal spines reduced to small denticles (SPI 0.01-0.05); dorsal face of propodeum short, but distinct; posterior face of propodeum gently sloping; petiole in dorsal view broadly oval, dorsolaterally rounded, without posterolateral tubercules or denticles; subpetiolar process variable; postpetiole bilobed with a broad median impression; subpostpetiolar process absent. Head sculpture aciculate; mesosoma, petiole, helcium and postpetiole reticulate; face usually with six to eight erect longer setae, and regular shorter, appressed pubescence; erect pilosity on promesonotum abundant, usually > ten setae; otherwise promesonotum dorsally with regular appressed to subdecumbent pubescence; propodeum laterally with two to four erect setae; petiole and postpetiole usually with a pair of long, erect setae posterolaterally, and shorter appressed pubescence; abdominal tergites and sternites four to seven with abundant short erect pilosity, and regular appressed to decumbent pubescence throughout. More or less bicolored: head, mesosoma, petiole and postpetiole reddish-orange to yellow, rest of metasoma black.
(n = 1) HW 1.25; HL 1.18; EL 0.40; SL 0.80; MSNW 1.13; MSNL 1.08; WL 1.97; SPL 0.00; PTH 0.33; PTL 0.42; PTW 0.47; PPL 0.30; PPW 0.47; LHT 0.93; CI 1.06; OI 0.34; SI 0.68; MSNI 1.04; SPI 0.00; PTHI 0.79; PTWI 1.14; PPI 1.59; LBI 2.12.
Small size (HW 1.25, WL 1.97). With worker characters, except as follows. Masticatory margin of mandibles with five teeth; antennal scapes surpassing level of lateral ocelli; eyes large (OI 0.34), situated at midline of head in full-face view; head shape square (CI 1.06); posterior margin straight. Mesoscutum in dorsal view as wide as long (MSNI 1.04); dorsal face of propodeum long and set off at right angle to posterior face; propodeal spines or tubercules absent; petiole moderately flared, postpetiole merely impressed behind; subpetiolar process variable. Sculpture aciculate throughout; face with eight longer erect setae (n = 1!) and abundant shorter erect to suberect pilosity; mesonotum with abundant short and scattered longer erect setae; petiole and postpetiole with dense short suberect pilosity, and postpetiole with additional longer dorso-posterior setae; abdominal tergites and sternites four to seven with abundant erect pilosity and appressed pubescence. Color as in workers; wings clear.
(n = 1) HW 0.57; HL 0.46; EL 0.22; SL 0.11; MSNW 0.69; MSNL 0.61; WL 1.24; SPL 0.00; PTH 0.17; PTL 0.22; PTW 0.22; PPL 0.14; PPW 0.24; LHT 0.60; CI 1.23; OI 0.47; SI 0.24; MSNI 1.14; SPI 0.00; PTHI 0.77; PTWI 0.99; PPI 1.64; LBI 2.07.
Small (HW 0.57, WL 1.24). Mandibles very short and reduced, blunt and edentate; clypeus fairly flat; eyes fairly large (OI 0.47) and protruding, midline of eyes situated well below midline of head, almost extending to clypeal margin; antennae 12-segmented; head wider than long (CI 1.23); in full-face view ocellar triangle situated at posterior head margin and elevated with respect to rest of face; occipital carinae distinct. Mesoscutum in dorsal view as wide as long (MSNI 1.14), scutellum in dorsal view broadly tapering from anterior to posterior end, dorsoposterior part rounded; metanotum not protruding from below scutellum; dorsal face of propodeum almost as long as posterior face; propodeal spines absent; petiole in dorsal view oval, laterally rounded, in lateral view anteriorly greatly tapering; subpetiolar process absent; postpetiole fairly flat and short, lacking median impression. Head sculpture reticulate; mesoscutum with very fine longitudinal carinulae; otherwise sculpture more or less shiny to aciculate; regular appressed to decumbent pubescence, and a few longer setae on face, mesoscutum, and scutellum; remaining pilosity as in queen. Color brown.
- Lectotype (designated by Blaimer & Fisher, 2013: 51), worker, Fianarantsoa, Madagascar, Dr. Besson, CASENT0101599, Musee d'Histoire Naturelle Genève.
- Paralectotype (designated by Blaimer & Fisher, 2013: 51), 5 workers, Fianarantsoa, Madagascar, Dr. Besson, Musee d'Histoire Naturelle Genève.
- Blaimer, B.B. & Fisher, B.L. 2013. Taxonomy of the Crematogaster degeeri-species-assemblage in the Malagasy region (Hymenoptera: Formicidae). European Journal of Taxonomy 51: 1-64 (DOI 10.5852/ejt.2013.51).
- Dalla Torre, K. W. von. 1893. Catalogus Hymenopterorum hucusque descriptorum systematicus et synonymicus. Vol. 7. Formicidae (Heterogyna). Leipzig: W. Engelmann, 289 pp. (page 86, Raised to species.)
- Emery, C. 1895g. Mission scientifique de M. Ch. Alluaud dans le territoire de Diego-Suarez (Madagascar-nord) (Avril-août 1893). Formicides. Ann. Soc. Entomol. Belg. 39: 336-345 (page 342, Raised to species)
- Emery, C. 1922c. Hymenoptera. Fam. Formicidae. Subfam. Myrmicinae. [part]. Genera Insectorum 174B: 95-206 (page 148, Combination in C. (Acrocoelia))
- 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 196, pl. 6, fig. 9 worker described)
- Mayr, G. 1895. Afrikanische Formiciden. Ann. K-K. Naturhist. Mus. Wien 10: 124-154 (page 138, raised to species)
- 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 (page 844, Combination in C. (Crematogaster))