Figures 1 - 7
TYPE MATERIAL
Holotype worker, Madagascar : Prov. Antsiranana , Foret d'Analabe , 30.0 km 72 ENE Daraina , 13 05 ' 00 " S , 049 54 ' 30 " E , 30 m, 27 Nov 2003 , littoral rainforest, (coll. B. L. Fisher et al.) Collection code: BLF 9426 , specimen code: CASENT 0041505 , ( CASC ) Paratypes : 1 worker and 1 dealate queen with same data as holotype but with specimen codes CASENT 0041506 (1 dQ) ( CASC ) and CASENT 0041507 (1 w) ( MCZC ) .
ETYMOLOGY
The specific name is an arbitrary combination, to be treated as a noun in apposition.
DESCRIPTION
Worker Measurements (mm): maximum and minimum based on all specimens, n = 22, (holotype), [paratype].
TL 2.3 - 2.76 (2.5) [2.5], HL 0.55 - 0.64 (0.60) [0.59], HW 0.37 - 0.43 (0.40) [0.40], LHT 0.34 - 0.46 (0.39) [0.39], CI 65 - 75 (67) [67], SL 0.36 - 0.44 (0.37) [0.37], SI 85 - 104 (91) [94], WL 0.69 - 0.87 (0.77) [0.75], PW (w) 0.28 - 0.36 (0.31) [0.31], DPW 0.17 - 0.22 (0.19) [0.19], PNI (w) 56 - 69 (62) [61], PH 0.25 - 0.32 (0.28) [0.27], PNL 0.24 - 0.32 (0.27) [0.28], LPI 86 - 104 (96) [104], PNH 0.20 - 0.23 [0.22], DPNL 0.20 - 0.25 [0.25], LPNI 96 - 117 [117].
Characters of Probolomyrmex worker as described by Brown (1975: 7). In full face view, posterior margin of head straight, lateral margins convex, posterolateral corners rounded. Mandible with apical tooth followed by a series of 6 small denticles. Palp formula 4,2. Eyes absent. Antennae 12 segmented.
General form of mesosoma and petiole as in figure 5. Dorsal outline of mesosoma in profile more or less straight, posterolateral corners of propodeum with blunt angles; posterior declivity of propodeum weakly concave in dorsal view. Dorsal sutures of mesosoma absent. Posterior face of petiolar node in lateral view more or less straight, with only a slight concave impression and enclosed laterally and dorsally by a low carina. Subpetiolar process developed as in figure 2; posteroventral portion projected into an acute angle (shape of posteroventral lamella variable in shape in specimens examined), without an acute tooth.
Cephalic dorsum with distinct punctures that overlay a surface of fine superficial punctures; both sizes of punctures separated by distances about equal to their average diameters. Superficial punctures also present on mesosoma and metasoma but less distinct. Mesosomal dorsum overlain with larger punctures similar in size to those on dorsum of head. Sides of mesosoma, petiole, and abdominal segments III and IV with shallow foveolate punctures. Head, mesosoma, metasoma finely shagreened and moderately shining. Pilosity typical for the genus and limited to opening of metapleural gland and mandibles. Pubescence whitish, extremely fine, adpressed and present over entire body, most abundant on abdominal sternites III and IV, and least developed on dorsum of mesosoma and underside of head. Color reddish brown
Queen measurements (mm): maximum and minimum based on all specimens, n = 3, [paratype].
TL 2.4 - 2.6 [2.6], HL 0.56 - 0.60 [0.60], HW 0.40 - 0.47 [0.42], LHT 0.32 - 0.41 [0.41], CI 67 - 83 [67], SL 0.33 - 0.39 [0.39], SI 80 - 99 [99], WL 0.71 - 0.80 [0.80], MW 0.32 - 0.36 [0.34], DPW 0.16 - 0.23 [0.2], PH 0.27 - 0.31 [0.28], PNL 0.24 - 0.29 [0.29], LPI 82 - 91 [91] PNH 0.19 - 0.24 (0.20) [0.20], DPNL 0.21 - 0.29 (0.24) [0.25], LPNI 101 - 121 (125) [122].
Characters of Probolomyrmex queen as described by Brown (1975: 7). General features as in figures 2, 4, and 6. Eyes large (maximum length of compound eye: 0.10 - 0.12), not convex, situated anterior to the midline of the head. Form of head, mandibles, and petiolar node as in worker. Surface sculpture, pubescence and color developed as in worker. General form of mesosoma as in figure 2. Based on specimen CASENT 0102226 from Berenty, wing venation highly reduced, as in previously described species (Taylor 1965).]
DISTRIBUTION AND BIOLOGY
P. tani is infrequently collected but widespread throughout western Madagascar (Fig. 7). This species has been collected most often in lowland (> 180 m) xeric habitats (littoral rainforest, tropical dry forest, and spiny bush). There are two examples, however, where the species has been collected in mesic forest: rainforest in Manongarivo (780 m) and mountain rainforest in Binara (1100 m). These two localities are nested within the western dry forest ecoregion and are adjacent to dry forest habitats. There are no records of Probolomyrmex from the large block of mesic forest in eastern Madagascar.
The type locality is a littoral forest in northeastern Madagascar. This was chosen as the type locality to draw attention to the importance of littoral forest in Madagascar. The remnant patches of littoral forest habitat along the northeastern coast north of Antalaha, such as Analabe and Ambondrobe, are rich in ant species and contain many endemics, but are highly threatened and without protective status. These forest patches do not harbor important vertebrate taxa and thus have not received priority status for conservation in Madagascar. Their rich arthropod fauna, however, should be recognized as an important component of diversity for reserve design (Simons et al., 2004).
The majority of specimens in this study were collected from sifted litter, but one specimen was obtained from under a stone, and one from a pitfall trap. These data suggest that this species nests and forages in soil or litter in a range of habitats from montane forest to dry spiny bush and rarely forages above ground. Unlike the other leaf litter nesting ants such as Strumigenys that demonstrate high species turnover across the island (Fisher 1999, 2000), Probolomyrmex tani has a wide distribution across many habitats. The subterranean habitat of this species may allow it to survive in a wide range of ecoregions.
DISCUSSION
Two specimens from the southwest of Madagascar (Tsimanampetsotsa: CASENT 0004401 (1 w) and Berenty CASENT 0102226 (1 aQ )) differ from other specimens from the north in lacking distinct shallow punctures on the mesosoma and metasoma. The queen from Berenty is also notably smaller HL 0.56 HW 0.40, LHT 0.32, and SL 0.33. Though the size and sculpture differences are notable, I consider the variation to be intraspecific.
P. tani is most similar to P. guineensis Taylor from Africa in size, and general shape. Workers of P. tani may be easily distinguished from those of P. guineensis by the shape of the posterior margin of the petiolar node in lateral view. In P. tani , the posterior margin is more or less straight, with only a slight concave impression, while in most other species including, P. guineensis , it is distinctly concave. In addition, the lateral and dorsal carina that encloses the posterior face of the petiolar node is more developed in P. guineensis than in P. tani . P. tani is easily distinguished from other ant genera and species in Madagascar by the absence of eyes in worker, and the presence of frontal lobes reduced to a narrow, sharp ridge between antennal sockets with antennal insertions clearly visible when viewed from the front.
OTHER MATERIAL EXAMINED
MADAGASCAR : Prov. Antsiranana , Foret d'Anabohazo , 21.6 km 247 WSW Maromandia , 14 18 ' 32 " S , 047 54 ' 52 " E , 120 m, tropical dry forest, 11 - 16 Mar 2001 (coll. Fisher et al.) - BLF 3338 : CASENT 0458322 (1 dQ), CASENT 0458323 (1 w) ; Foret de Binara , 9.4 km 235 SW Daraina , 13 15 ' 48 " S , 049 36 ' 00 " E , 1100 m, montane rainforest, 5 Dec 2003 (coll. B. L. Fisher et al.) - BLF 98000 : CASENT 0043467 (1 w), CASENT 0043468 (1 w), CASENT 0043471 (1 w) ; Montagne des Francais , 7.2 km 142 SE Antsiranana (= Diego Suarez ), 12 19 ' 22 " S , 049 20 ' 17 " E , 180 m, tropical dry forest, 22 - 28 Feb 2001 (coll. Fisher et al.) - BLF 3123 : CASENT 0004400 (1 w) ; R. S. Manongarivo , 12.8 km 228 SW Antanambao , 13 58 ' 36 " S , 048 25 ' 24 " E , 780 m, rainforest, 11 Oct 1998 (coll. B. L. Fisher et al.) - BLF 1862 (15) - 5 (1 w) Mahajanga , Parc National d'Ankarafantsika , Ampijoroa Station Forestiere , 40 km 306 NW Andranofasika , 16 19 ' 15 " S , 046 48 ' 38 " E , 130 m, tropical dry forest, 26 Mar-1 Apr 2001 (coll. Fisher et al.) - BLF 3522 : CASENT 0465467 (1 dQ), CASENT 0465863 (1 w) ; Parc Nationale d'Ankarafantsika Nationale , Ampijoroa Station Forestiere , 5.4 km 331 NW Andranofasika , 16 17 ' 56 " S , 046 48 ' 47 " E , 70 m (coll. Fisher et al.) - BLF 3571 : CASENT 0469570 (1 w), CASENT 0469571 (1 w), CASENT 0469572 (1 w), CASENT 0469573 (1 w), CASENT 0469574 (1 w), CASENT 0469575 (1 w), CASENT 0469576 (1 w), CASENT 0469577 (1 w), CASENT 0469578 (1 w), CASENT 0469579 (1 w) ;; Parc National Tsingy de Bemaraha , 3.4 km 93 E Bekopaka , Tombeau Vazimba , 19 08 ' 31 " S , 044 49 ' 41 " E , 50 m, 6 - 10 Nov 2001 (coll. Fisher et. al.) - BLF 4232 : CASENT 0477984 (1 w), CASENT 0477985 (1 w), CASENT 0477986 (1 w) ; Toliara , Parc National de Tsimanampetsotsa , Foret de Bemanateza , 20.7 km 81 E Efoetse , 23.0 km 131 SE Beheloka , 23 59 ' 32 " S , 043 52 ' 50 " E , 90 m, spiny forest / thicket, 22 - 26 Mar 2002 (coll. Fisher et. al.) - BLF 6263 : CASENT 0004401 (1 w) ; Toliara , Berenty 12 km N. W. Amboasary, 5 - 15. v. 1983 . (col. J. S. Noyes , M. C. Day ) - BM. 1983 - 201: CASENT 0102226 (1 aQ) .
