Crematogaster tricolor

Identification
A member of the Crematogaster degeeri group. The tricoloration of this species serves to uniquely identify this species from all other Crematogaster species in the C. degeeri-assemblage. Beyond the color, the mostly very long propodeal spines (SPI 0.10-0.26) are also useful diagnostic characters. (Blaimer and Fisher 2013)

Key to Crematogaster degeeri group workers /  queens

Distribution based on Regional Taxon Lists
Afrotropical Region: Comoros, Kenya, Mozambique. Malagasy Region: Mayotte.

Nomenclature

 *  tricolor. Crematogaster tricolor Gerstäcker, 1859: 263 (w.) MOZAMBIQUE. [Also described as new by Gerstäcker, 1862: 515.] Forel, 1887: 388 (q.m.). Combination in C. (Acrocoelia): Emery, 1922e: 145. Junior synonym of castanea: Mayr, 1907b: 16; Emery, 1915g: 12; Wheeler, W.M. 1922a: 830. Revived from synonymy as subspecies of castanea: Arnold, 1920a: 489; Emery, 1922e: 145; Santschi, 1926b: 213. Raised to species: Blaimer & Fisher, 2013: 55.

Description
Blaimer and Fisher (2013):

Worker
(n = 20) HW 0.71-1.27; HL 0.65-1.14; EL 0.16-0.26; SL 0.54-0.88; WL 0.73-1.37; SPL 0.08-0.30; PTH 0.16-0.30; PTL 0.20-0.37; PTW 0.23-0.47; PPL 0.11-0.25; PPW 0.18-0.39; LHT 0.54-0.96; CI 1.10- 1.19; OI 0.21-0.25; SI 0.77-0.83; SPI 0.10-0.26; PTHI 0.60-0.80; PTWI 1.07-1.26; PPI 1.46-1.85; LBI 1.30-1.45.

Small to large size (0.71-1.27, WL 0.73-1.37), usually large. Masticatory margin of mandibles with four teeth; head shape usually wider than long (CI 1.10-1.19); posterior margin of head in full-face view laterally subangular, medially depressed; occipital carinae distinct; antennal scapes reaching or surpassing head margin; midline of eyes situated above midline of head in full-face view; eyes fairly large (OI 0.21-0.25) and strongly protruding. Pronotum laterally angular; promesonotal suture indistinct; mesonotum often slightly raised with respect to pronotum, and with a median tubercule or carinae; mesonotum usually with a short posterior face; laterally mesonotum angular, 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 short to medium-sized (SPI 0.10-0.26), straight and moderately diverging; dorsal face of propodeum as long as posterior face; posterior face of propodeum gently sloping; petiole in dorsal view moderately flared and concave, dorsolaterally rounded, without posterolateral tubercules or denticles; subpetiolar process variable; postpetiole narrowly bilobed with a sharp median impression; subpostpetiolar process absent. Head and mesosomal sculpture areolate; petiole, helcium and postpetiole dorsally and ventrally reticulate; erect pilosity on face scarce, usually less than four erect longer setae, and regular, shorter, appressed pubescence; erect pilosity on promesonotum scarce, usually only two to four humeral setae; otherwise promesonotum dorsally with regular appressed to subdecumbent pubescence; petiole and postpetiole usually with a pair of short, erect setae posterolaterally, and shorter appressed pubescence; abdominal tergites four to seven with sparse, short, erect pilosity, more abundant and longer on sternites four to seven, and abundant appressed to decumbent pubescence throughout. Distinctly tricolored: Head and mesosoma reddish-orange, first half of abdominal segment four yellow, rest black.

Queen
(n = 8) HW 1.61-1.77; HL 1.38-1.49; EL 0.44-0.49; SL 0.98-1.10; MSNW 1.20-1.45; MSNL 1.32-1.46; WL 2.43-2.69; SPL 0.00-0.04; PTH 0.38-0.44; PTL 0.42-0.57; PTW 0.57-0.67; PPL 0.36-0.40; PPW 0.57-0.64; LHT 1.13-1.30; CI 1.14-1.21; OI 0.31-0.33; SI 0.69-0.74; MSNI 0.85-1.04; SPI 0.00-0.02; PTHI 0.72-1.05; PTWI 1.18-1.53; PPI 1.41-1.69; LBI 1.98-2.30.

Medium size (HW 1.61-1.77, WL 2.43-2.69). With worker characters, except as follows. Masticatory margin of mandibles with five teeth; antennal scapes reaching or surpassing level of lateral ocelli; eyes fairly large (OI 0.31-0.33), situated at midline of head in full-face view; head distinctly wider than long (CI 1.14-1.21), tapering from anterior to posterior margin; posterior margin straight. Mesoscutum in dorsal view longer than wide, or as wide as long (MSNI 0.85-1.04); dorsal face of propodeum short; propodeal tubercules present; petiole moderately flared, postpetiole merely impressed behind; subpetiolar process variable. Sculpture carinulate on face and propodeum, otherwise aciculate throughout; face usually with > six longer erect setae 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 often with additional, longer dorso-posterior setae; abdominal tergites and sternites four to seven with abundant appressed pilosity and sparse, short, erect pilosity. Tricoloration is similar to workers, but less distinct; wings clear.

Male
(n = 3) HW 0.73-0.82; HL 0.54-0.60; EL 0.27-0.31; SL 0.10-0.15; MSNW 0.80-0.95; MSNL 0.77-0.91; WL 1.40-1.78; SPL 0.00; PTH 0.21-0.24; PTL 0.25-0.29; PTW 0.27-0.31; PPL 0.18; PPW 0.28-0.35; LHT 0.73-0.91; CI 1.32-1.36; OI 0.50-0.53; SI 0.19-0.26; MSNI 1.01-1.04; SPI 0.00; PTHI 0.80-0.83; PTWI 1.05-1.10; PPI 1.59-1.91; LBI 1.92-2.00.

Small (HW 0.73-0.82, WL 1.40-1.78).

Mandibles short (not touching when closed) with two regular-sized teeth; clypeus fairly flat; eyes large (OI 0.50-0.53) and protruding, midline of eyes situated well below midline of head, almost extending to clypeal margin; antennae 12-segmented; head wider than long (CI 1.32-1.36); 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 1.01-1.04); scutellum in dorsal view broadly tapering from anterior to posterior end, dorsoposterior part rounded; metanotum protruding from below scutellum; dorsal face of propodeum almost as long as posterior face; propodeal spines absent; propodeal spiracle situated in a margined depression on propodeum; 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 to carinulate; mesoscutum with very fine longitudinal carinulae; otherwise sculpture more or less shiny to aciculate; abundant, short, erect pilosity, but very few longer setae on face, mesoscutum, and scutellum; remaining pilosity as in queens. Color brown.

Additional References

 * 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).
 * [[Media:Gerstacker 1859.pdf|Gerstäcker, A. 1859. [Untitled. Introduced by: "Hr. Peters berichtete über sein Reisewerk, von dem die Insecten bis zum 64., die Botanik bis zum 34. Bogen gedruckt sind und theilte den Schluss der Diagnosen der von Hrn. Dr. Gerstäcker bearbeiteten Hymenopteren mit."]. Monatsber. K. Preuss. Akad. Wiss. Berl. 1858: 261-264 PDF]]