Myopias

Myopias is a moderately large genus (more than 40 described species) restricted to Southeast Asia and Australia. Relatively little is known about its habits, but at least some are specialist predators of millipedes. They are known to nest in rotten wood on the ground and form large midden piles containing beetle parts and millipede segments.

Identification
Schmidt and Shattuck (2014) - Workers of Myopias are distinctive and unlikely to be mistaken for any other genus. Diagnostic characters of the genus (in combination) include: linear mandibles, blunt medial clypeal projection (absent in some species), round propodeal spiracles, nodiform petiole, strong gastral constriction, and simple tarsal claws. The clypeal projection and simple tarsal claws separate Myopias from Leptogenys, the morphologically most similar (and phylogenetically closest) genus. Buniapone and Paltothyreus also have blunt medial clypeal projections, but they differ in many other characters and are unlikely to be confused with Myopias.

Probst et al. (2015) - Males Among Palearctic and Indomalayan Ponerinae, Myopias may be recognized by the following combination of characters: 1) Antennal sockets situated high on head, about two socket diameters from posterior clypeal margin; 2) compound eyes nearly circular in profile view; 3) hindwing anal cell shorter than maximum basal cell width; 4) jugal lobe absent; 5) notauli present; and 6) abdominal tergum VIII apex not spiniform.

Distribution
Probst et al. (2015) - The genus Myopias occurs in most of the Oriental, Indo-Australian, and Australasian regions, ranging from northern India (Jammu & Kashmir state) to Tasmania in Australia. The genus is particularly diverse in New Guinea (17 described species) and some Indonesian islands (Sumatra, 9 species) with some species known only from the Mentawei islands (M. maligna punctigera and M. papua). Myopias is much more widespread than previously thought (Ogata, 1992), in particular for continental Asia and the Indian sub-continent, the western part of Australia, or the Solomon Islands. However, much work on this genus remains to be done before a complete picture is attained of its distribution and diversity within different regions as illustrated by the lack of records of Myopias in several countries (Cambodia, Laos, Vietnam) or Chinese provinces (Guangdong, Guangxi, Hainan) where it might possibly occur. A recent review of Ponerinae of Vietnam did not mention any collection of the genus, but Myopias still figured as a potential genus to be found in the generic key provided therein (Eguchi et al., 2014). More species are also in need of description as shown by the four Myopias morphospecies recorded from the Solomon Islands (Sarnat et al., 2013) or from other regions.

Species by Region
Number of species within biogeographic regions, along with the total number of species for each region.

Biology
Schmidt and Shattuck (2014) - Myopias is a poorly known genus, probably due to its cryptic nesting and foraging habits. Most of what is known about its ecology and behavior comes from anecdotal observations. Nests are generally constructed in rotting wood, though some species are subterranean nesters (Wheeler, 1923b; Willey & Brown, 1983). Reported colony sizes are typically less than 100 workers, and often much less (Wilson, 1959a; Willey & Brown, 1983; Gobin et al., 2006). At least some species are polygynous, and ergatoid queens (in conjunction with normal dealate queens) occur in at least two species (Myopias concava and an undescribed Indonesian species; Willey & Brown, 1983; Gobin et al., 2006). Workers of Myopias emeryi are obligately sterile (Gobin et al., 2006). Males have apparently never been reported for any Myopias species, which could simply be a reflection of the paucity of observations of any kind for this genus, or may suggest an unusual reproductive strategy. The feeding habits of most species are unknown, but some species are specialist predators of millipedes (Wilson, 1959a; Willey & Brown, 1983) and M. delta is a specialist predator of ants (especially myrmicines but also other ponerines). Gobin et al. (2003b) identified subepithelial glands in M. emeryi and Myopias maligna which may function in hydrocarbon production. Abdominal glands within a number of Myopias species were examined by Billen et al. (2013), leading to the discovery of several glands which were previously unknown in ants.

Probst et al. (2015) - Probably due to cryptic behavior, almost all information about Myopias natural history comes from circumstantial observations (Schmidt & Shattuck, 2014). Ecological information on Myopias species is thus scarce and scattered within the literature. Colonies are relatively small, with less than a hundred workers, and occur in rotten logs in rainforests or in the soil next to rocks in sclerophyll woodlands (Billen et al., 2013). Gyne number observed in collected nests varies and some species could be considered as polygynous (e.g., M. chapmani, M. concava, M. emeryi, M. maligna) (Willey & Brown, 1983; Billen et al., 2013) although formal investigation of functional polygyny is still necessary at this point. Wheeler (1923) argued that the highly vestigial eyes in the workers of these ants could indicate subterranean habits. In his study of the New Guinea ant communities, Wilson (1959) included Myopias species (n=6) as ground-stratum nesters, allocating them to the category of “residents of small pieces of rotting wood”, but it should be noted that some species are known as subterranean nesters (Wheeler, 1923; Willey & Brown, 1983). Wilson (op. cit.) also presented reasons why this microhabitat is favored by ants; for example, pieces of wood tend to maintain uniform and favorable conditions of temperature and humidity. In the Lower Basu River of the Huon Peninsula, New Guinea, Wilson (1976) found that Myopias together with genera Odontomachus, Leptogenys, Cerapachys, Myrmecina, Cardiocondyla, Pristomyrmex, Triglyphothrix (=Tetramorium), and Leptomyrmex, constitute 10–15% of all colonies found in what he called the ground zone, which includes soil nesters (ants nesting exclusively or extending their nests from the soil into rotting logs) plus residents of small pieces of wood.

Little is known about the feeding habits of Myopias, but some species are considered specialist predators of millipedes (Schmidt & Shattuck, 2014). Wilson (1959) classified two New Guinea species of Myopias (possibly M. concava and M. julivora) as millipede predators and estimated colony sizes as 60 and 40-70 workers, respectively. Wilson generalized that specialist predators tend to have the smallest colonies as a function of diversity and local abundance of food supply. Billen et al. (2013) studied Myopias emeryi, Myopias maligna, and “M. sp.1”, all species from Padang, Indonesia, and Ulu Gombak, Malaysia, and classified them as millipede predators, although the authors didn’t give any information on feeding habits or nest remains of these species. In their revision of Myopias, Willey and Brown (1983) gave some information on the behavior of these ants. They suggested that M. gigas could be a millipede predator, based on the long mandibles and large size. Two nests of M. julivora were found with remains of millipedes in the brood chamber and nest galleries; the prey all seemed to belong to the same group. For M. concava, the authors mentioned that one colony inside bark contained an unidentified insect larva and a live adult beetle, possibly a cucujoid. Unfortunately, the residue from Wilson’s collection was lost. Regarding M. tenuis, the most common and widespread species (see Table 1), a worker carrying an entomobryid collembolan and a nest having cuticular fragments of an unidentified arthropod are mentioned by Willey and Brown (1983). Myopias delta is reported as a specialist predator of ants and according to Willey and Brown (1983), Wilson’s notes mentioned a colony with a small decapitated worker of a Leptogenys species and the remains of at least two myrmicine genera. Again, those food remains were lost in transit. Recruitment to collect food resources has never been reported to the best of our knowledge, but has been hypothesized for M. emeryi and M. maligna based on the presence of subepithelial glands, which are associated with recruitment in ants (Gobin et al., 2003), and on trail-following behavior observed in M. maligna and an undescribed species (Billen et al., 2013).

Nomenclature

 *  MYOPIAS [Ponerinae: Ponerini]
 * Myopias Roger, 1861a: 39. Type-species: Myopias amblyops, by monotypy.
 * Myopias junior synonym of Pachycondyla: Snelling, R.R. 1981: 389.
 * Myopias revived from synonymy: Willey & Brown, 1983: 249.
 * Myopias senior synonym of Trapeziopelta, Bradyponera: Willey & Brown, 1983: 249.
 * BRADYPONERA [junior synonym of Myopias]
 * Bradyponera Mayr, 1886c: 362. Type-species: Ponera nitida (junior primary homonym in Ponera, replaced by Trapeziopelta mayri), by monotypy.
 * [Bradyponera Smith, F. 1873: viii. Nomen nudum, attributed to Mayr.]
 * Bradyponera junior synonym of Pachycondyla: Snelling, R.R. 1981: 389 (error).
 * Bradyponera junior synonym of Trapeziopelta: Emery, 1911d: 93 (provisional synonym); Donisthorpe, 1932c: 468.
 * Bradyponera junior synonym of Myopias: Willey & Brown, 1983: 249].
 * TRAPEZIOPELTA [junior synonym of Myopias]
 * Trapeziopelta Mayr, 1862: 715. Type-species: Ponera maligna, by monotypy.
 * Trapeziopelta senior synonym of Bradyponera: Donisthorpe, 1932c: 468.
 * Trapeziopelta junior synonym of Pachycondyla: Snelling, R.R. 1981: 390.
 * Trapeziopelta revived status as genus: Wheeler, G.C. & Wheeler, J. 1985: 256.
 * Trapeziopelta junior synonym of Myopias: Willey & Brown, 1983: 249; Bolton, 1994: 164.

Worker
Small to large (TL 2.8–16.9 mm) ants with the standard characters of Ponerini. Mandibles usually narrow and moderately curved (triangular in Myopias delta), with only a few teeth, often without a distinct basal angle, and with a strong basal groove. Clypeus very shallow, the frontal lobes reaching or surpassing the anterior clypeal margin, which usually has a small blunt anterior projection. Eyes very small to moderate in size (rarely absent), located far anterior of the head midline. Mesopleuron not divided by a transverse groove (though sometimes with a row of foveae giving the impression of a groove). Metanotal groove shallow to deep. Propodeum broad dorsally. Propodeal spiracles small and round. Metatibial spur formula (1s, 1p). Petiole nodiform, widening posteriorly and dorsally. Gaster with a strong girdling constriction between pre- and postsclerites of A4. Presence of stridulitrum on pretergite of A4 variable. Head and body foveolate or smooth and shining, sometimes with lateral striations on the mesosoma. Head and body with scattered pilosity and little to no pubescence. Color variable, yellow to black.

Queen
Similar to worker but usually slightly larger (sometimes smaller, as in M. chapmani), alate and with the other caste differences typical for ponerines (Willey & Brown, 1983). Ergatoid queens occur in at least some species, e.g. Myopias concava.

Male
Probst et al. (2015) - 1) Lateral hypostomal margin unmodified.

2) Palpal formula 6,3; 5,3; 4,3.

3) Antennal toruli situated high on head, at least two antennal socket diameters from posterior clypeal margin.

4) Compound eye subspherical

5) Occipital carina present, short.

6) Notauli strongly impressed, meeting or nearly meeting at body midline, not extending posteriorly after meeting.

7) Oblique mesopleural sulcus present.

8) Epimeral lobe present, completely obscuring meso-spiracle.

9) Propodeal spiracle small, circular to elliptical.

10) Propodeal lobe present, variably developed.

11) Metacoxal cavities closed.

12) Tibial spur formula 2(1s-b,1b-p),2(1s-b,1p).

13) Pretarsal claws well-developed, hooked, edentate.

14) Costal region of forewing margin linear.

15) Venation Ogata type I or IIa (submarginal cells 1 and 2 closed, Mf2 may be reduced to absence).

16) Pterostigma well-developed.

17) Costal vein present.

18) Rs+M and Rsf2+3 tubular (submarginal cell 1 closed).

19) 2rs-m and Mf3+ tubular (submarginal cell 2 closed).

20) Marginal cell 1 closed, somewhat short: Length only slightly greater than that of submarginal cell 1.

21) 1m-cu present (discal cell 1 closed).

22) Subdiscal cell 1 closed or open.

23) Hindwing venation somewhat reduced, free abscissae R, Rs, M, and Cu spectral to absent. (When apical-most portion of free M absent, basal cell enclosed distally by 1rs-m+M).

24) Hindwing subbasal cell shorter than maximum basal cell width.

25) Jugal lobe absent.

26) Hindwing claval region reduced.

27) Petiole subfusiform to nodiform, apex of node at or posterior to petiole midlength.

28) Petiolar sternum linear in profile view, with anteroventral denticle.

29) Helcium infraaxial, narrow.

30) Prora of abdominal sternum III transverse, with variable longitudinal carinae extending from posterior margin.

31) Cinctus between abdominal pre- and post-sclerites IV distinct.

32) Striduletrum of abdominal pretergite IV present.

33) Abdominal tergum VIII visible in situ, apical margin linear to convex, not spiniform.

34) Abdominal sternum VIII visible in situ.

35) Abdominal sternum IX ligulate, apex linear to convex.

36) Pygostyles present.

Comments on diagnosis 

The diagnostic characters presented above are derived from intergeneric comparison of Myopias with Ponerinae on a global scale, with many characters evaluated due to value recognized in a treatment of the New World males (Boudinot in prep.). At the specific level, while some male-based morphospecies of Myopias are more easily differentiated than others it seems that Myopias males are character-rich and should be relatively easy to delimit with sufficient sampling. Each character provided here and for the male of Myopias darioi is derived from comparison with the eight morphospecies and the males of Myopias chapmani, Myopias maligna, and ''Myopias tenuis, and should serve as a scaffold for parsing species-level boundaries. Additional subtle variation was observed during this study but was not characterized due to the limited scope of this work.

A general picture of male interspecific variation is here developed based on comparative study of the eight morphospecies and three species. The examined species and morphospecies differ in coloration (whole body, wings and veins), body size and eye size, head shape, details of venation, mesonotum features, propodeal sculpture, size and shape of the petiole, genitalia, and characters of the metasoma. Of these body regions the petiole, propodeum, and genitalia vary most significantly. Body form of male Myopias seems relatively stable, with the mesosoma not undergoing drastic modification interspecifically. Additionally, setation seems quite stable, being most variable on the head and legs; no or only very sparse appressed pubescence was observed on the morphospecies. Variation of propodeal sculpturation took these forms: A) Propodeum smooth with posteropropodeum delimited by an arcing carina (with infraspecific variation where this carina may be obliterated by stronger longitudinal carinae on the posterior face that do not extend to the metasoma) (most common form found); B) Propodeum weakly to strongly rugose, in the weakly rugose morphospecies the rugulae extend slightly up the dorsopropodeum from the posteropropodeum, while in the strongly rugose morphospecies the entire propodeum is covered; C) Dorsopropodeum with a pair of longitudinal weakly arcuate carinae extending from the metanotum to the posterior propodeal face, which is delimited by an arching carina (characteristic of one morphospecies). The propodeum also varies in shape and size; other variation occurs, but these features were observed to have most separatory value. The petiole varies from low, long, and asymmetrically fusiform (spindle-shaped), to very small with a distinct node and short peduncle. In one morphospecies the petiolar node is strong and swollen appearing, with the anterodorsal and dorsal surfaces evenly and strongly convex, nearly overhanging the posterior tergal face. Variation of the petiole is not as discrete, however, as in the propodeum. All genitalic sclerites showed characteristic variation in the species and morphospecies examined.

Larva
Larvae of some Myopias species have been described by Wheeler & Wheeler (1964, 1976).

Etymology
Myopias (mi-op" i-as) Gr. myopias 'a short-sighted person' (Wheeler, G.C. 1956)