Thaumatomyrmex fraxini

Colonies of this species inhabit small cavities in the leaf litter, with a preference for snail shells. This very small species is not a strict predator of Penicillata (Myriapoda, Diplopoda), but also capture specimens of Collembola (Hexapoda, Insecta), not so much small comparatively to its size. This species forms very small colonies without queen.

Identification
D’Esquivel et al (2017) - Differs from all other known species by the unique combination of the following characters:

1. Head in dorsal view, with cephalic capsule subquadrate, slightly longer than wide (CI = 88.1-98.3).

2. Maximal width of head less than 1,5 times the maximal width of pronotum (PI = 130-147.4).

3. Maximal width of frons greater than that of pronotum.

4. Mesosoma in lateral view, with outline of the dorsal face of mesonoto-propodeal complex drawing a single convexity (metanotal groove and suture absent), weak and symmetrical.

5. Mesosoma in lateral view, with outline of the dorsal face of mesonoto-propodeal complex separated from that of the postero-lateral margin of propodeum by a nearly right angle.

6. Propodeum with postero-lateral margins sharply marked and straight, nearly angulated but without defining any carinae.

7. Segment abdominal 2 (petiole) in lateral view, with the node not differentiating a dorsal face, the outline of anterior face meeting that of posterior face in an acute angle.

8. Mandible with a proximal tooth well differentiated (triangular shaped, as long as wide basally).

9. Mandibles slightly shorter than the maximal head width in front of eyes (MI3 = 86.8-98.2).

10. Mandibles slightly shorter or longer than the maximal length of femur (MI2 = 88.9-111.1).

11. Median part of clypeus smooth and shining.

12. Lateral parts of clypeus with longitudinal carinae.

13. Frontal lobes with longitudinal carinae.

14. Front mostly smooth and shining, except its more anterolateral parts at the posterior end of frontal carinae with dense longitudinal rugulae.

15. Vertex smooth and shining.

16. Genae smooth and shining, except the supra-ocular areas with some longitudinal microrugulae.

17. Mesosoma smooth and shining.

18. Metasoma smooth and shining.

19. Clypeus with two pair of erect setae (long, slightly curved, forward directed, thin, only apically acute) situated at lateral margin of anterior half of clypeus, the most anterior being one third longer.

20. Postero-lateral margins of propodeum with two erect setae (long, strongly curved, inward directed, thin, only apically acute).

If using the taxonomic identification key of Kempf (1975), Thaumatomyrmex fraxini differs from Thaumatomyrmex contumax and Thaumatomyrmex mutilatus by its diagnostic characters 1, 11, 13, 14, 15, 16, 17, 18 and 19 (see dichotomy 1 and 2). Moreover, T. fraxini also differs from these species by its diagnostic characters 5 and 6. Also, T. fraxini differs from Thaumatomyrmex cochlearis Creighton, 1928 by its diagnostic characters 11, 14, 16, 17, 18 and 20 (see dichotomy 1 and 2). Finally, T. fraxini may not be any one of the species keyed at dichotomy 4 (Thaumatomyrmex atrox; Thaumatomyrmex ferox; Thaumatomyrmex manni, Thaumatomyrmex paludis and Thaumatomyrmex zeteki) because of its diagnostic character 5 and 6. Moreover, T. fraxini differs from T. atrox, T. ferox and T. manni by its diagnostic characters 1 and 4. Also, T. fraxini differs from T. zeteki by its diagnostic characters 4.

Considering the Thaumatomyrmex species described posteriorly to the revision of Kempf (1975), T. fraxini differs from Thaumatomyrmex bariay by its diagnostic characters 1, 5, 7 and 14. Also, T. fraxini differs from Thaumatomyrmex mandibularis by its diagnostic characters 1, 5, 7 and 14. Thaumatomyrmex fraxini differs from Thaumatomyrmex nageli by its diagnostic characters 5 and 7. Thaumatomyrmex fraxini differs from Thaumatomyrmex soesilae by its diagnostic characters 1 and 2.

We attempted to attribute Thaumatomyrmex fraxini to one of the species groups proposed by Kempf (1975). We concluded that this new species may not belong to the mutilatus or cochlearis groups, since it exhibits several incoherence’s with their respective definition. Thus, T. fraxini differs from the members of the mutilatus group by the following morphological characteristics: different patterns for the sculpture (diagnostic characters 11 to 18) and chaetotaxy (diagnostic characters 19 and 20). Also, T. fraxini differs from members of the cochlearis group by the following morphological characteristics: a different petiolar shape (diagnostic character 7); a different pattern for the sculpture (diagnostic characters 11, 14 and 15); a different pilosity on propodeum (character 20). Moreover, the small denticle present at basis of apical tooth of mandible in T. fraxini lacks in all species of the cochlearis group. Finally, we could attribute this new species to the ferox group since it morphology agrees with the definition of this (see diagnostic characters: 4, 7,11, 13-18, 19, 20). Inside the ferox group, it should be noted that T. fraxini is morphologically more similar to T. paludis and T. zeteki (subgroup 1 sensu Kempf (1975)) than to other members since it shares exclusively with these two species a subquadrate head shape (diagnostic character 1; CI [95] {88,1-98,3}), a similar interfrontal index (IFI [70,2] {64,3-75}), a more similar petiole in scalelike shape (diagnostic character 7) and some mandibles with apex not noticeably projecting laterad beyond genae when in closed position. After all, T. fraxini seems to be more related to Thaumatomyrmex paludis since these two species share exclusively a mesosomal shape without a metanotal suture and transverse groove (see diagnostic character 4).

Finally, beside the morphological peculiarities of this new species above discussed, the comparison of its morphometrical pattern with all other valid species reveals that T. fraxini is the smaller species of the genus.

Distribution
Thaumatomyrmex fraxini is only known from the states of Bahia and Sergipe in Brazil, with a geographic distribution limited to a latitudinal range between 11°21’S - 16°15’S and a longitudinal range between 37°25’W - 40°43’W. Its altitudinal distribution reaches 1010m. It is encountered in several types of native forests in the Central corridor of the Atlantic Forest biome where it may be locally sympatric either with Thaumatomyrmex mutilatus or Thaumatomyrmex contumax. Also, T. fraxini may be found in agroecosystem like cocoa plantation, and in others anthropic environments.

Distribution based on Regional Taxon Lists
Neotropical Region: Brazil.

Nomenclature

 *  mutilatus. Thaumatomyrmex mutilatus D'Esquivel & Jahyny, in D'Esquivel et al., 2017: 161, figs. 1-4 (w.) BRAZIL.

Worker
here we provide some complementary descriptive elements of the morphology of this new species through the presentation of high resolution microphotographs (see figures 1-12) and the following morphometric data: Data for holotype given in [brackets]; means with standard deviations for paratypes (n=15) given in (parenthesis); maximum range for paratypes (n=15) given in {brace}. EL [0.17] (0.16±0.01) {0.14 – 0.18), GL [1.11] (1.10±0.14) {0.95 – 1.47), HFL [0.50] (0.52±0.03) {0.45-0.57}, HL1 [0.60] (0.59±0.02) {0.55-0.62}, HL2 [0.58] (0.55±0.02) {0.52-0.58}, HW1 [0.57] (0.55±0.02) {0.52–0.59}, HW2 [0.57] (0.56±0.02) {0.54–0.60}, IFW [0.40] (0.39±0.02) {0.36-0.42}, ML [0.52] (0.51±0.03) {0.46-0.57}, PTH [0.55] (0.46±0.05) {0.40-0.55}, PTL [0.32] (0.26±0.02) {0.23-0.32}, PTW [0.52] (0.48±0.03) {0.44-0.54}, PW [0.41] (0.40±0.01) {0.38-0.42}, SL [0.43] (0.41±0.02) {0.40-0.45}, TL [2.86] (2.77±0.17) {2.57-3.19}, WL [0.83] (0.81±0.03) {0.73-0.86}. Indices: CI [95] {88.1- 98.3}, IFI [70.2] {64.3-75}, MI1 [86.7] {79.3-95}, MI2 [104] {88.9-111.1}, MI3 [91.2] {86.8-98.2}, PI [139] {130-147.4}.

Type Material
Type material. Holotype: one worker deposited in and labeled:  LBSA_SA_14015217, Brazil: Bahia, Belmonte, Barrolândia, CEPLAC/EGREB, 16°5’33.04”S, 39°12’17.64”W, elev. 109 m and Col. S. Lacau, L.B. Godinho, M.R. da Silva Jr, M.L. Oliveira, 05.09.2008. Paratypes (n=28): 2 workers with the same data as Holotype, in CPDC (LBSA_SA_14015192, LBSA_SA_14015582); 1 worker Brazil: Bahia, Ilhéus, and Col. J. Maia, 07.06.1996, in CPDC (LBSA_SA_14015569); 1 worker Brazil: Bahia, Ilhéus, CEPEC and Col. P. Terra, 14.04.1987, in CPDC (LBSA_SA_14015570); 1 worker Brazil: Bahia, Ilhéus, Cacaual and Col. J.C.S. Carmo, 05.1998, in CPDC (LBSA_SA_14015572); 1 worker Brazil: Bahia, Ilhéus, CEPEC and Col. J.C.S. Carmo, 04.1996, in CPDC (LBSA_SA_14015573); 1 worker Brazil: Bahia, Ilhéus, CEPEC, Zoologia and 10.07.1998, in CPDC (LBSA_SA_14015580); 2 workers Brazil: Bahia, Ilhéus, Banco do Pedro, 144051 S, 0391524 W and Col. J.R.M. Santos, J.C.S. do Carmo, 12.01.1998, in CPDC (LBSA_SA_14015571, LBSA_SA_14015583); 2 workers Brazil: Bahia, Ilhéus and Col. J.C.S. Carmo, 06.1997, in CPDC (LBSA_SA_14015574, LBSA_SA_14015575); 3 workers Brazil: Bahia, Ilhéus, Olivença and Col. V.R.L. Mello, 06-09.08.1996, deposited in CPDC (LBSA_ SA_14015576, LBSA_SA_14015577),  (LBSA_ SA_14015578) and  (LBSA_SA_14015579); 2 workers Brazil: Bahia, Camacan and Col. J.R.M. dos Santos, 27.08.1999, in CPDC (LBSA_SA_14015592, LBSA_SA_14015593); 2 workers Brazil: Bahia, Una and Col. J.R.M. dos Santos, 24.08.1998, in CPDC (LBSA_ SA_14015612, LBSA_SA_14015613); 1 worker Brazil: Bahia, Mascote and Col. J.R.M. dos Santos, 18.06.1999, in CPDC (LBSA_SA_14015562); 2 workers Brazil: Bahia, Canavieiras, Oiticica and Col. J.R.S. Carmo, 30.03.1998, in CPDC (LBSA_SA_14015563, LBSA_SA_14015564); 3 workers Brazil: Bahia, Canavieiras, Oiticica, Col. J.C.S.Carmo, J.R.M. Santos, 09.10.1998, in CPDC (LBSA_ SA_14015565), MZSP (LBSA_SA_14015566) and MPEG (LBSA_SA_14015567); 3 workers Brazil: Bahia, Itapebi and Col. J.R.M Santos, 16.07.1997, in CPDC (LBSA_SA_14015609, LBSA_SA_14015610, LBSA_ SA_14015611); 1 worker Brazil: Bahia, Santa Cruz Cabrália, 455321 S, 8203867 W and Col. J.R.M. Santos, J.C.S. Carmo, 08.08.2006, in CPDC (LBSA_SA_14015568).

Etymology
This species is named in honor to the Professor Dominique Fresneau, a French ethologist who devoted his life studying the behavior of Neotropical ponerines. The specific name “fraxini” is the genitive of Fraxinus, the Latin genus name of the ash tree (Oleaceae) described by Linnaeus, 1753. The family name Fresneau is an old French name for these trees.