Tetramorium latreillei Forel,

Hita Garcia, F. & B. L. Fisher, 2012, The ant genus Tetramorium Mayr (Hymenoptera: Formicidae) in the Malagasy region - taxonomic revision of the T. kelleri and T. tortuosum species groups., Zootaxa 3592, pp. 1-85 : 69-71

Tetramorium latreillei Forel, 1895

(Figs. 16, 23, 126, 127, 128, 142)

Tetramorium (Xyphomyrmex) latreillei Forel, 1895:247. Lectotype worker [designated here] MADAGASCAR, est Imerina ("eastern Imerina") (Sikora) (BMNH: CASENT0102340) [examined]. Paralectotypes, two workers with same data as lectotype (MHNG: CASENT0101291, CASENT0101292) [examined].

[Note: Bolton (1979) noted that all syntypes were located in the Forel collection in MHNG. However, we also found one syntype (the newly designated lectotype) in BMNH with the additional information "remounted B. Bolton 1975".]

Diagnosis

Tetramorium latreillei is clearly recognisable within the T. smaug complex because it is the only species without any standing hairs on the first gastral tergite.

Description

HL 1.05-1.06 (1.06); HW 1.06-1.08 (1.07); SL 0.82-0.85 (0.84); EL 0.23-0.24 (0.24); PH 0.52-0.55 (0.53); PW 0.72-0.76 (0.74); WL 1.37-1.40 (1.38); PSL 0.54-0.56 (0.55); PTL 0.34-0.35 (0.35); PTH 0.41-0.43 (0.42); PTW 0.27-0.30 (0.29); PPL 0.30-0.32 (0.31); PPH 0.43-0.45 (0.44); PPW 0.40-0.44 (0.42); CI 100-101 (101); SI 77-79 (79); OI 22 (22); DMI 53-55 (54); LMI 38-39 (39); PSLI 50-53 (52); PeNI 38-39 (39); LPeI 81-85 (83); DPeI 79-86 (83); PpNI 55-58 (56); LPpI 70-72 (71); DPpI 132-138 (134); PPI 141-148 (145) (three measured).

Head as long as wide to weakly wider than long (CI 100-101); posterior head margin strongly concave. Anterior clypeal margin medially impressed. Frontal carinae strongly developed, diverging posteriorly, and ending at corners of posterior head margin. Antennal scrobes well-developed, moderately deep, but narrow, and without defined posterior and ventral margins. Antennal scapes short, not reaching posterior head margin (SI 77-79). Eyes of moderate size (OI 22). Mesosomal outline in profile flat, moderately marginate from lateral to dorsal mesosoma; promesonotal suture and metanotal groove absent; mesosoma comparatively stout and high (LMI 38-39). Propodeal spines massively developed with very broad base, extremely long, and acute (PSLI 50-53); propodeal lobes short and rounded. Petiolar node in profile rectangular nodiform, around 1.2 times higher than long (LPeI 81-85), anterior and posterior faces approximately parallel, anterodorsal and posterodorsal margins approximately at same height, dorsum slightly convex; node in dorsal view between 1.1 to 1.3 times longer than wide (DPeI 79-86). Postpetiole in profile subglobular, weakly anteroposteriorly compressed, approximately 1.4 times higher than long (LPpI 70-72); in dorsal view around 1.3 to 1.4 times wider than long (DPpI 132-138). Postpetiole in profile appearing less voluminous than petiolar node, in dorsal view about 1.4 to 1.5 times wider than petiolar node (PPI 141-148). Mandibles distinctly longitudinally rugose; clypeus longitudinally rugose, with three to five rugae; cephalic dorsum between frontal carinae with 9 to 12 longitudinal rugae, most rugae running unbroken from posterior head margin to anterior clypeus, few rugae interrupted or with cross-meshes; lateral and ventral head longitudinally rugose, rarely with cross-meshes. Mesosoma laterally and dorsally distinctly longitudinally rugose. Forecoxae with very distinct and pronounced longitudinal rugae. Waist segments longitudinally rugose, rugae on waist segments weaker than on head and mesosoma, especially dorsally. Gaster completely unsculptured, smooth, and shining. Ground sculpture generally faint to absent everywhere on body. Head with abundant standing hairs; mesosoma with up to two pairs restricted to pronotal dorsum; remainder of mesosoma, waist segments, and first gastral tergite without standing hairs; first gastral tergite with moderately dense appressed pubescence. Anterior edges of antennal scapes with appressed hairs. Body a uniform very dark brown to black colour.

Notes

Unfortunately, no modern material is available. The original type series is from "eastern Imerina" (Forel, 1895), which might be located in central-eastern Madagascar. The exact type locality remains unknown, making it difficult to resample new material. It is surprising, though, that no more specimens have been collected in the last 120 years, especially considering the large sampling effort undertaken by the Malagasy ant inventory project (Fisher, 2005).

Within the species complex, T. latreillei is the only species lacking standing hairs on the first gastral tergite, and is thus easily identifiable. Even without cons idering this character, it cannot be misidentified with T. adamsi due to the petiolar node of the latter, which has the posterodorsal margin higher than the anterodorsal margin. Shorter antennal scapes separate T. latreillei from T. nazgul (SI 89-93), and the very dark brown to black colouration distinguishes it from T. marojejy, which is of orange colour. However, T. latreillei is very close to T. sabatra and T. smaug. All three species share the same morphometric range, and superficially possess a similar overall habitus. They have massively constructed, extremely long propodeal spines, reduced hairiness, and very dark brown to black colouration. This character combination clearly separates these three species from the remainder of the complex. As noted above, T. latreillei can be easily separated from T. sabatra and T. smaug by the pilosity/pubescence on the first gastral tergite. The latter two have only very sparse, short pubescence and few to many long, standing hairs on the first gastral tergite, whereas T. latreillei does not have a single standing hair, but instead a moderately dense, appressed pubescence.

It is possible that all three species are conspecific, and that the differences in pilosity/pubescence represent geographical variation. The overall morphological similarity might support this hypothesis, as well as the fact that none of the three species was found in sympatry. However, our own studies (Hita Garcia et al., 2010; Hita Garcia & Fisher, 2011, 2012), as well as previous studies on Tetramorium (Bolton, 1976, 1977, 1979, 1980), concur that pilosity and pubescence patterns are generally very species-specific. The hairs on the mesosoma and first gastral tergite represent a particularly good diagnostic character. Tetramorium latreillei, T. sabatra and T. smaug all seem to be relatively rare, making them unlikely to be found in the same locality. The distribution ranges of the three, however, strongly overlap. We currently consider all three distinct species that can be well separated, although the species delimitations presented herein might change with additional material.

Material examined

MADAGASCAR: Imerina (Sikora).