Simopone

Garcia, Wiesel and Fischer (2013) - The recent revision by Bolton and Fisher (2012) places the taxonomy of the genus in excellent condition. Good identification keys are available for workers and queens. Simopone seem to be rare, arboreal ants and presumably are nocturnal (Bolton, 1973a; Brown, 1975; Kutter, 1977; Bolton & Fisher, 2012). Knowledge about the natural history is very limited but from some species it is known that they are specialised predators of other ants (Brown, 1975; Bolton & Fisher, 2012).

Identification
Key to Malagasy Simopone Species

Distribution
Simopone is distributed in the Afrotropical, Malagasy, Oriental, and Indo-Australian regions although most are are found in the Afrotropical and Malagasy regions.

Species richness
Species richness by country based on regional taxon lists (countries with darker colours are more species-rich). View Data



Nomenclature

 *  SIMOPONE [Cerapachyinae: Cerapachyini]
 * Simopone Forel, 1891b: 139. Type-species: Simopone grandidieri, by monotypy.
 * Simopone subgenus of Cerapachys: Forel, 1892l: 243.
 * Simopone revived status as genus: Dalla Torre, 1893: 17.

Bolton and Fisher (2012):

Worker
Shared characters of the genera Simopone, Vicinopone and Tanipone - As well as the 20 features that are exhibited by all members of Cerapachyini these three genera share the following suite of seven characters in the worker caste. None of the characters is claimed as synapomorphic for the three, or for any two of the three.

1 Pretarsal claws with a single preapical tooth, at least on the metatarsus.

2 Mesotibial spurs absent (at most a setiform vestige may remain that cannot be distinguished by light microscopy from other setae at the tibial apex).

3 Metatibial spur single, pectinate.

4 Eyes present and conspicuous, always large (EL/HW 0.30–0.53).

5 Apical antennomere subcylindrical, not inflated and bulbous.

6 Ventrolateral margin of head without a continuous longitudinal carina that commences close to anterior margin below the mandible and extends the entire length of the head to the posterior margin (a carina is present posterolaterally that usually extends onto the ventral surface).

7 Frontal lobes widely separated by the relatively broad clypeus; frontal lobes not or only slightly elevated laterally on each side of the clypeus (never closely approximated and vertical).

Predominantly arboreal cerapachyine ants (workers occasionally found foraging on ground or in rotten wood). Workers of most (perhaps all) species exhibit considerable size variation. With the shared characters of Cerapachyini and also with the following combination of characters. Two undoubted apomorphies of the genus are in italics.

1 Palp formula 6,4 or 5,3. Maxillary palp of moderate length: with mouthparts retracted the apex of the maxillary palp, when extended back on underside of head, does not reach beyond the level of the posterior margin of the eye.

2 Mandibles triangular, either edentate, bluntly denticulate, or with small, low, blunt crenulations at least on the basal half; mandibles without a basal groove and without a basal pit.

3 Antenna with 11 segments, gradually incrassate apically; apical antennomere large but subcylindrical, not swollen and bulbous, its maximum width generally no greater than that of the preapical segment.

4 Scape short (SI 33–56); when laid straight back in full-face view the scape apex merely reaches the level of the anterior margin of the eye or slightly beyond.

5 Eyes large (EL/HW 0.30–0.53), located from slightly in front of, to distinctly behind, the midlength of the head.

6 Ocelli present; usually distinct but may be small, inconspicuous and flush with the surface of the head.

7 Clypeus broad and more or less flat across; broadly inserted between frontal lobes.

8 Frontal lobes and carinae present; frontal lobes at most only weakly elevated and in full-face view conceal at least the inner margins of the antennal sockets; frontal carinae usually extend back to at least the level of the anterior margins of the eyes; frontal carinae never abruptly truncated posteriorly and never terminated immediately behind the frontal lobes.

9 Parafrontal ridges variably developed, sometimes absent.

10 Head capsule without a differentiated vertical posterior surface above the occipital foramen; instead the vertex slopes evenly down to the upper margin of the occipital foramen, which is visible in full-face view.

11 Head capsule, in ventral or ventrolateral view, with a carina that extends down the posterolateral margin and onto the ventral surface, where it terminates or fades out well before meeting the ventral midline; this carina is anterior to, and separate from, that which borders the occipital foramen.

12 Mesosoma dorsally with at least a transverse vestige of promesonotal suture; metanotal groove usually absent, although sometimes vestigially present to obvious.

13 Pronotum in dorsal view bluntly angulate to carinate anteriorly between anterior surface and dorsum; propodeum rounded to carinate between dorsum and declivity.

14 Mesosoma laterally usually with an impression or pit near the metapleural-propodeal junction, on approximately the same level as the propodeal spiracle.

15 Midpoint of metanotal groove (or midpoint of dorsum at that level if groove absent) with a pit or impression.

16 Mesotibia without spurs.

17 Metatibia with a single, pectinate spur.

18 Metatibial gland absent (at least no external orifice or indication is present).

19 Metabasitarsus ventrally with a longitudinal glandular groove that occupies at least the basal half of the tarsomere length.

20 Pretarsal claws of all legs with a single preapical tooth on the inner surface of each claw.

21 Propodeal lobe in profile broad-based, bluntly triangular or rounded apically.

22 AII (petiole) flattened or shallowly convex dorsally; angulate to marginate laterally in dorsal view; often with a longitudinal carina on the side above the level of the spiracle.

23 AIII broadly postpetiolate, more voluminous than AII (petiole) but usually smaller than AIV.

24 Prora of AIII a simple curved cuticular rim or carina that separates the anterior face of the poststernite from its lateral and ventral surfaces.

25 Pretergite of AIV in dorsal view strongly constricted with respect to posttergite of AIV.

26 Cinctus of AIV smooth, without cross-ribs.

27 Tergite of AIV without a pair of subovate glandular patches on the posterior half.

28 Pygidium variable in structure at its apex: either apical margin evenly curved and equipped with a row of 4–6 minute denticles; or apex with one or two pairs of somewhat enlarged teeth that are flanked by smaller teeth; or apex with a short but stout, bifid cuticular fork that is much more strongly developed than any other teeth on the margin.

Comments on worker characters (Numbers correspond to character numbers above)

1 Palp formula 6,4 was established by dissection in workers of conradti, dux, nonnihil, rex, sicaria, silens, trita and wilburi, and by in situ counts of everted mouthparts in grandis, latiscapa, marleyi, miniflava and persculpta. Palp formula 5,3 was established by dissection in elegans and grandidieri. In some other species the palp formula could be estimated even though the mouthparts were retracted (e.g. PF 6,4 in annettae, brunnea, dryas) but in some, and especially in specimens mounted flat on card, the mouthparts were obscured and PF could not be counted.

3 In most species all funicular segments except the apical are conspicuously broader than long, but in laevissima and some extralimital species of the grandidieri group segments 4–6 appear at least as long as broad.

4 SI range includes all directly measured Afrotropical and Malagasy species. Among the extralimital species, chapmani has SI 33 (holotype measured), bakeri has SI 37 (MCZC gyne measured), oculata has SI ca 42 (estimated from Radchenko, 1993: 46, fig. 5) and gressitti has SI ca 41 (estimated from Taylor, 1965: 4, fig. 2).

5 In the schoutedeni group many conspicuous short setae arise between the ommatidia of the eye. Elsewhere in the genus such setae are much more sparse and usually indistinct, but in most species a few can be detected at high magnification.

7 In most members of the emeryi group the clypeus is very obviously strongly reflexed, so that the true anterior clypeal margin, at the clypeo-labral junction, is considerably below and behind the apparent anterior clypeal margin as seen in full-face view. The lateral portions of the clypeus, in front of the antennal sockets, tend to be flattened or evenly rounded in members of the grandidieri group, the schoutedeni group, and in grandis and persculpta of the emeryi group. In the remainder of the emeryi group the margin is produced anteriorly as a rounded lobe or short, blunt triangle in front of each socket, but these projections are reduced in trita and silens.

9 Parafrontal ridges (sensu Wilson, 1964, Borowiec, 2009; = genal carinae sensu Bolton, 2003) are usually distinctly present in the grandidieri group and the schoutedeni group, where they appear as fine carinae that extend back almost to the eye. In the emeryi group their development is more variable. They may be entirely absent or represented only by a slight tumulus immediately behind the clypeus (e.g. conradti, marleyi, rex, silens), or weakly present but short and inconspicuous (e.g. dignita, latiscapa, merita, persculpta, victrix). They are never extended backwards to near the anterior margin of the eye.

11 In direct contrast to the situation in Simopone, in both other genera treated here, Tanipone and Vicinopone, the carina extends to the ventral midline.

12 Promesonotal suture is sometimes vestigial or mostly absent from the dorsum (elegans, grandidieri), or it may be merely a weak impression or a fine, slightly incised line (consimilis, dignita, emeryi, marleyi); most often its track is indicated by a row of short cuticular ribs or linked punctures across the dorsum, which may be conspicuous or very faint (conradti, laevissima, latiscapa, rex and the schoutedeni group). The metanotal groove is sometimes absent, but often it is represented by a weak to vestigial transverse line (conradti, grandis, inculta, latiscapa, rex); only very rarely is it obviously, though shallowly, impressed (chapmani, laevissima).

13 Anterodorsally the pronotum may be merely angulate between its anterior and dorsal surfaces (rex, silens) but in most it is distinctly marginate to carinate. However, the pronotal dorsum never rounds broadly and evenly into its anterior surface.

14 This impression or pit perhaps represents the last visible trace of the metapleural spiracle on the surface of the mesosoma. It is quite conspicuous in the majority of species but is small and indistinct, or even absent, in the Afrotropical laevissima and the Malagasy species elegans, emeryi, fera, grandidieri, merita and nonnihil.

15 The median pit is usually distinct but may be small and inconspicuous in conradti and grandis, and may be difficult to distinguish from the predominant sculpture in those species of the schoutedeni group that have dense foveolate punctures on the dorsal mesosoma.

16 Apex of the mesotibia usually has one to several setae that are roughly aligned in the direction of the long axis of the shaft. It is probable that one of these represents the last vestige of a spur.

18 The metatibia, at the base of the pectinate spur, usually shows a small translucent patch of cuticle, or a small cuticular vesicle. This appears to be associated with the articulation of the spur and is not part of a metatibial gland structure. In large, strongly sclerotised species such as rex and silens, the small translucent patch is usually not apparent.

19 The ventral metabasitarsal groove is conspicuous in all species. It varies from a narrow slit to a broad trench that occupies well over half the width of the tarsomere and is often filled with white to yellowish flocculent material. Elsewhere in Formicidae a similar groove is exhibited only by Paraponera (Paraponerinae), Myrmecia and Nothomyrmecia (Myrmeciinae), and Tetraponera and Myrcidris (Pseudomyrmecinae) (summarised in Bolton, 2003).

20 The preapical tooth on each pretarsal claw is conspicuous on all legs in larger species, but may be small and more difficult to see in small species, especially on the forelegs, but is always present.

22 Tergite of abdominal segment AII (petiole) shows a wide range of structures. Transverse carinae may be present anterodorsally, posterodorsally, or both, where the dorsum meets the anterior and posterior surfaces. The lateral surface of AII often has a curved longitudinal carina that extends its length. This carina is located below the dorsolateral margination but above the level of the spiracle. In the grandidieri group it is sometimes short and confined to the area in front of and above the spiracle (elegans, grandidieri) but it is entirely absent in bakeri, chapmani and laevissima. In the emeryi group it is usually present but is weak in conradti and marleyi, and absent in dignita, dux, sicaria and victrix. In the schoutedeni group it is universally present and generally strongly developed. The posterior corners of AII are frequently extended into lobes or teeth that project posteriorly or laterally.

24 In a few species, for instance grandidieri, laevissima and some members of the schoutedeni group, the prora is only feebly developed ventrally.

25 In dorsal view the maximum width of the pretergite of AIV is 0.52–0.69 × the maximum width of the posttergite of the segment. The ratio in Vicinopone falls within the same range (0.62–0.64) but the pretergites of Tanipone species are relatively much wider, 0.76–0.89. This ratio has not yet been investigated in other cerapachyine genera.

28 Pygidial armament varies among the three species groups recognised within the genus. In the grandidieri group the posterior pygidial margin is lined with an arc of small, usually peg-like denticles that are all approximately the same size, without an enlarged pair apically. In the schoutedeni group the posteromedian pair or two pairs of denticles on the arc are somewhat enlarged, immediately above the sting. In the emeryi group the margin of the pygidium is produced posteriorly into a short but stout cuticular fork that is very obviously larger and more strongly developed than any marginal denticle.

Queen
Known queens are entirely worker-like except that the mesosoma has a full complement of flight sclerites. Therefore all the worker characters listed above, except for numbers 12 and 15, are duplicated here. Queens are known for the Afrotropical species annettae, conradti, latiscapa, marleyi, matthiasi, miniflava, persculpta, wilburi, and for the extralimital species bakeri; most specimens are dealate. No queen recognisable by external morphology has been seen in any Malagasy species, the queens of which are suspected to be remarkably ergatoid, or perhaps even replaced by gamergates, but proof of this must await dissection of reproductive systems to assess the presence of spermathecae and enlarged ovaries. For venation, see discussion of character 15 under males.

Male
Of the Malagasy species males are known for dux, mayri, nonnihil, rex, silens and seven unassociated forms of the emeryi group, and also for grandidieri of the grandidieri group. The males of two species are known from the Afrotropical region, marleyi and an unassociated male of the schoutedeni group. No males have been recorded for any of the extralimital taxa.

1 Palp formula 6,4 or 5,3.

2 Mandibles triangular and edentate, masticatory margins straight to shallowly concave, meeting at full closure.

3 Antenna 12-segmented, filiform; funicular segments 3 to apex longer than broad; apical segment the longest, tapering apically and not swollen, longer than funicular segment 11 but no broader.

4 Eyes large and very conspicuous.

5 Ocelli present.

6 Frontal lobes and frontal carinae present and strongly developed; lobes somewhat elevated on each side of the relatively broad clypeus but concealing at least the inner margins of the antennal sockets in full-face view.

7 Head capsule, in ventral or ventrolateral view, with a carina that extends down the posterolateral margin and onto the ventral surface, where it terminates or fades out well before meeting the ventral midline.

8 Pronotum slightly to very conspicuously visible in dorsal view.

9 Notauli present.

10 Parapsidal grooves present.

11 Propodeal lobes present and conspicuous.

12 Mesotibia without spurs.

13 Metatibia with a single, pectinate spur.

14 Pretarsal claws each with a preapical small tooth.

15 Venation as discussed below.

16 Prora present as a transverse cuticular flange.

17 AIII postpetiolate, with AIV > AIII > AII.

18 Pygidium with posterior margin not denticulate.

Comments on male characters

Too few males are known to give as detailed a diagnosis as the workers, but the listed characters should serve to successfully isolate Simopone males from other cerapachyines. Numbers below correspond to character numbers above.

1 PF 6,4 has been confirmed by dissection or in situ count in dux, marleyi, rex, silens and three unassociated Malagasy species; PF 5,3 was confirmed by in situ count of grandidieri.

3 In all males except the one from the schoutedeni group the length of funicular segment 4 is equal to or > 3 > 2 > 1; in the schoutedeni group male funiculus segment 4 is about equal to 3, and 2 is about equal to 1, with 1 and 2 shorter than 3 and 4. The scape in all known Malagasy species of the emeryi group has a flange-like or broadly tooth-like prominence apically, in front of the insertion of the first funicular segment. This is not developed in marleyi, grandidieri, or the schoutedeni group male.

4 In the schoutedeni group male the short, bristly setae that arise between the ommatidia, which are so obvious in workers and queens, are absent.

8 Two quite distinct degrees of pronotal exposure are exhibited. In all the known Malagasy males the pronotum, in dorsal view, merely forms a narrow collar in front of the mesoscutum, as is also the case in Tanipone. But in the Afrotropical marleyi and in the unassociated male of the schoutedeni group the visible pronotum forms an extensive, transverse sclerite in front of the mesosocutum. The midline length of the pronotum (its narrowest point) is 0.25 (marleyi)–0.35 × the midline length of the mesoscutum. By contrast, in Malagasy males the pronotum is only 0.10–0.15 × the mesoscutum midline length.

15 Wing venation is best represented in larger males, such as those of mayri, rex and silens. Diagnostically, on the forewing the pterostigma is large and pigmented, usually strongly so; C is absent; R1•f3 is a short stub or absent distal of the pterostigma; 2rs-m is absent; Rs•f2-3 is faint, sometimes spectral, detached basally from Rs+M so that its base floats freely in the membrane; 2r-rs and Rs•f4-5 are usually weakly developed and sometimes very faint indeed, and the latter does not distinctly meet the wing margin; 2r-rs may occasionally be absent; 1m-cu is usually present but may be very faint; cu-a arises from M+Cu (before it splits into M•f1 and Cu•f1); M fades out distally. In smaller males and in the only known alate queen (annettae) the forewing venation shows reduction from this pattern until the wing is veinless from a point well proximal of the pterostigma to the margin except for Sc+R1, linked to the pterostigma. On the hindwing rs-m is always absent.