Crematogaster tricolor Gerstäcker, 1859

Blaimer, Bonnie B. & Fisher, Brian L., 2013, Taxonomy of the Crematogaster degeeri-species-assemblage in the Malagasy region (Hymenoptera: Formicidae), European Journal of Taxonomy 51, pp. 1-64 : 55-59

Crematogaster tricolor Gerstäcker, 1859 stat. rev.

Figs 22-23

Crematogaster tricolor Gerstäcker, 1859: 263 (w.) [also described as new by Gerstäcker 1862: 515].

Crematogaster tricolor – Forel 1887: 388 (q.m.).

Crematogaster tricolor , junior synonym of Crematogaster castanea – Mayr 1907: 16. — Emery 1915: 12. — Wheeler 1922a: 830.

Crematogaster castanea tricolor – Arnold 1920: 489. — Emery 1922: 145. — Santschi 1926: 213.

C. (Acrocoelia) tricolor – Emery 1922: 145.

Diagnosis

The tricoloration of this species (see Fig. 22B, C ) 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. Sequence divergence between C. tricolor stat. rev. and the remaining species ranges from 16.6 - 22.2 % ( Table 3 ).

Type material examined

( ZMHB): MOZAMBIQUE: Tete (S. Peters), one worker; lectotype worker by present designation: CASENT0104590, image on AntWeb.

Other material examined

( BBBC, CASC, MCZC, PSWC, ZMHB): refer to Supplementary Material 1.

Worker

Measurements

(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.

Description

( Fig. 22A - C ) 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

Measurements

(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.

Description

( Figs 22D - F ) 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

Measurements

(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.

Description

( Fig. 23A, C ) 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.

Distribution and biology

MADAGASCAR, COMOROS, MAYOTTE, MOZAMBIQUE [East Africa?]. Crematogaster tricolor stat. rev. was originally described from Mozambique (see comments), but we limit ourselves here to its description in the Malagasy region. The species has been recently collected in scrublands of coastal areas and urban and disturbed habitats in northern, eastern and central Madagascar, and in Comoros and Mayotte, occuring at elevations from 0 m to 1240 m ( Fig. 23B ). Collections in native habitat have been made in dry forest and littoral forest in northern Madagascar. Crematogaster tricolor stat. rev. co-occurs usually with C. dentata stat. nov., C. maina sp. nov. and C. lobata , and at a few localities also with C. sewellii , C. mafybe sp. nov. and C. masokely sp. nov. Very few colonies have been collected from dead twigs above ground, indicating that this species has an arboreal nesting habit.

Comments

We raised Crematogaster tricolor from subspecies to species status considering the following points.

1) We examined the syntype specimens of C. castanea tricolor in ZMHB and found them to be conspecific to our recent collections from the Malagasy region.

2) We examined images of syntype specimens of C. castanea Smith , which are available on AntWeb (CASENT0102953), and found them to be a good match for specimens one of us (B. Blaimer) had received from a colleague collected in Mozambique.

3) Both this C. castanea material and the C. tricolor material from Madagascar were included in a molecular biogeographic study on Crematogaster ants ( Blaimer 2012b), where the sequences of these specimens proved to be divergent and clearly not conspecific.

In this study, we limit ourselves to describing the presence of C. tricolor stat. rev. in the Malagasy region, although the species should still occur on the African mainland. Recent ant collections from Mozambique are poor, and historic collections are in such disarray for this genus that they would be only manageable to cite in a large scale taxonomic project on African Crematogaster , which is not the focus of this project. Moreover, apart from C. tricolor stat. rev., there are 18 further subspecies currently listed by Bolton (2012) for C. castanea , described from all over East and Central Africa, that would need to be revised during such a comprehensive undertaking.

The predominant occurrence of this species in urban and disturbed habitats, and the two distinct clades in the mitochondrial data with different affinities to the Comoros and Mayotte populations ( Fig. 2 , see above) suggest that this species was only recently introduced to Madagascar.

Figures

Fig. 22. Crematogaster tricolor Gerstäcker, 1859 stat. rev., worker and queen. A-C. Worker (CASENT0120944). A. Full-face. B. Profile. C. Dorsal. D-F. Queen (CASENT0120949). D. Full-face. E. Profile. F. Dorsal.

Fig. 23. Crematogaster tricolor Gerstäcker, 1859 stat. rev., male and distribution. A, C. Male (CASENT0136505). A. Full-face. C. Profile. B. Species distribution.

Fig. 2. Relatedness of populations between Madagascar and the wider Malagasy region. Subsets of the same phylogeny as shown in Fig. 1, with broad geographical origin of sequenced individuals mapped onto the tree for: A. Crematogaster maina sp. nov. B. Crematogaster dentata stat. nov. C. Crematogaster tricolor stat. rev. Support values in black represent posterior probabilities (pp), those in blue ML bootstrap values> 70 and those in red ML bootstrap values <70. Values pp <0.96 are not shown; nodes not present in the ML analysis are represented by a dash instead of a bootstrap value. The scale bar shows nucleotide changes per base pair. Distance between Madagascar and Islands is not drawn to scale. Appended numbers on taxon labels represent CASENT#’s of respective voucher specimens.