Sphinctomyrmex

Brown, W. L., 1975, Contributions toward a reclassification of the Formicidae. V. Ponerinae, tribes Platythyreini, Cerapachyini, Cylindromyrmecini, Acanthostichini, and Aenictogitini., Search: Agriculture; Cornell University Agricultural Experiment Station 15, pp. 1-115 : 31-33

Sphinctomyrmex

> Sphinctomyrmex Mayr, 1866: 895, [[ queen ]]. Type: Sphinctomyrmex stali , 1866, monobasic. ----- Borgmeier, 1957: 104, [[ worker ]] ', discussion of S. stali .

[[ ... ]] Cerapachys : Forel, 1893: 461, not F. Smith.

> Eusphinctus Emery, 1893, Ann. Soc. Entomol. France, 61 (1892): cclxxv, [[ worker ]]. Type: Eusphinctus furcatus , 1893, by original designation, monobasic. ----- 1895 a: pl. 14, fig. 4, [[ male ]]: genitalia.

> Sphinctomyrmex subgenus Eusphinctus : Emery, 1894 b: 457. ----- 1911: 7, [[ worker ]] [[ queen ]], species list.

> Eusphinctus : Wheeler, 1918: 219, 224, review of Australian spp. with key.

> Eusphinctus subgenus Eusphinctus : Wheeler, 1918: 219, diagnosis; 224 - 231, review of Australian spp. with key.

> Eusphinctus subgenus Zasphinctus Wheeler, 1918: 219, 233. Type: Eusphinctus (Zasphinctus) turneri Forel, monobasic.

> Euphinctus subgenus Nothosphinctus Wheeler, 1918: 219, 225, 233 - 239, diagnosis and review of Australian spp. with key. Type: Sphinctomyrmex froggatti Forel , by designation of Donisthorpe, 1943, Ann. Mag. Natur. Hist., (11) 10: 675.

> Aethiopopone Santschi, 1930: 49, a. Type: Sphinctomyrmex rufiventris Santschi , monobasic.

Worker: With characters of Cerapachys , but gastric segments IV, V, and VI separated by distinct constrictions and (except for S. furcatus and S. taylori ) nearly equal in length. Eyes reduced to very small size or altogether lacking (except in s. turneri , which has fairly large, convex eyes). Antennae with 11 or 12 segments; palpi usually segmented 3,3. Sculpture of round piligerous foveolae, sparse or crowded, with smooth or finely roughened interspaces. Hairs short, simple, sparse to fairly dense; pubescence sometimes present on petiole, postpetiole, or succeeding gastric segments. Color black, brown, red, or yellow.

Queen: A morphocline ranges from perfect winged (or dealate) females with large eyes, ocelli, etc., to blind subdichthadiiform queens that are workerlike except for larger size and broader head and petiole, and sometimes vestigial eyes and 1 ocellus. Intermediates exist in, e. g., S. steinheili and S. asper ; these may have compound eyes of modest size and 3 ocelli, but workerlike trunk. It seems likely that the species with subdichthadiiform queens have monogynous colonies, while at least some of the dealate or intermediate forms are found several (to more than 20) to a single colony. It is not known whether the multiple queens are all functional reproductives.

Male: Differs from Cerapachys male by the distinctly constricted subequal segments of the gaster, and even here a difficulty exists because some American Cerapachys have narrowed bases to the main gastric segments. The male of S. furcatus , like its worker, has the gastric segments unequal, with the first much the largest. Antennal segments 13, rarely ( S. furcatus ) 12.

Aside from s. furcatus , males of Sphinctomyrmex divide into 2 classes. The first class, associated in a few cases with workers and / or queens ( S. steinheili , S. turneri , S . asper ) has slender males with triangular mandibles, and usually distinct notauli. The second class, consisting of males taken at light, probably belongs with the species having subdichthadiiform queens (froggatti group); these have long, tapered, falcate mandibles and lack distinct notauli; they tend to be larger and relatively robust, and have denser, softer, more regularly arranged pilosity, particularly on head and mandibles (figs. 97, 98); see also fuller discussion at [67].

The genus Sphinctomyrmex was first described by Mayr (1866: 895) from a single dealate queen with 12 - segmented antennae ( S. stali ) from southeastern Brasil. Although at least one winged queen of Sphinctomyrmex had already been collected in West Africa in the last century [70], the genus was not to be reported in print from that continent again until Santschi's record of 1915. Forel described forms from Australia (as Cerapachys ) in 1893 and 1895, and in 1895 Emery introduced the new generic name Eusphinctus for a worker from Burma with 11 - segmented antennae that he named E. furcatus . New Eusphinctus species were added from New Guinea by Emery (1897) and from India and Australia by Forel, who both saw that workers of some species had 11, others 12, antennal segments, and therefore regarded Eusphinctus only as a subgenus of Sphinctomyrmex . Andre (1905) noted that the Indo-Australian species known at the time differed from the lone neotropical species, S. stali , in that they had ergatoid queens, whereas the S. stali queen had well-developed thoracic sclerites and had obviously once borne wings. On this basis, he recommended that Sphinctomyrmex and Eusphinctus be recognized as separate genera. Emery, in his 1911 ponerine fascicle of the Genera Insectorum, kept Eusphinctus at subgeneric level. In 1918, however, Wheeler not only embraced Andre's generic separation, but went on to subdivide Eusphinctus into 3 subgenera:

1. Eusphinctus s. str. Workers and females with 11 - jointed antennae, with entire or emarginate pygidium, the workers blind, the females with eyes and ocelli. Habits hypogaeic.

2. Nothosphinctus subgen. nov. Workers and females with 12 - jointed antennae; the former blind and with entire pygidium, the latter with emarginate pygidium and either blind or with very minute eyes and the anterior ocellus. Habits hypogaeic.

3. Zasphinctus subgen. nov. Workers large, dark colored, with 12 - jointed antennae and well developed eyes, but without ocelli. Females unknown. Habits probably epigaeic.

Meanwhile, Santschi (1915) had described a species of Sphinctomyrmex from males taken at light in West Africa. Wheeler (1918) dismissed Santschi's generic assignment as " open to doubt. " But when Santschi read Wheeler's 1918 revision, he displayed his carefree notion of generic-level taxonomy by making S. rufiventris the type of a new genus, Aethiopopone , and justified his action as follows (Santschi En 1915, quand je decrivis cette espece en la rapportant au genre Sphinctomyrmex , l'habitat de celui-ci etait considere comme etant le Bresil, l'Australie et l'Indie, et le S etait encore inconnu. Or, le [[ male ]] de S. rufiventris avec ses caracteres de Prodorylinas, surtout ses segments abdominaux etrangles, son habitat intermediaire, me fit risquer une identification pareille a celle que firent Forel et Emery en rapportant a ce genre les Eusphinctus du vieux monde. Ce n'est du reste qu'en 1918 que Wheeler fit la distinction generique, ne considerant plus que comme Sphinctomyrmex la [[ queen ]] S. stali Mayr du Bresil. En elevant au rang de genre le sous-genre Eusphinctus Em. pour les especes indo-australiennes, il le divise en trois sous-genres: Eusphinctus , Notosphinctus et Zasphinctus . Cela etant donne, je me vois oblige de creer un nouveau genre pour l'espece africaine. Les caracteres de celle-ci tiennent das G. Sphinctomyrmex , Cerapachys et Simopone .

This house of cards should have been fluttered away in 1923 by Clark when he described Eusphinctus occidentalis from Western Australia. This species turned out to have a dealate queen with 11 - segmented antennae associated with blind workers much like those of the eastern Australian E. steinheili and E. duchaussoyi .

Further discoveries were the worker caste of S. stali (Borgmeier, 1957) [69] and the winged Sphinctomyrmex queen collected long ago by Afzelius in West Africa [70], already mentioned above, and also workers of Sphinctomyrmex dug out of the Ivorian savanna by Jean Levieux [70]. Now another species has been found by Gotwald in rotting wood in Gabon (unpublished).

It seems from a survey of all the old and new material that we are dealing with a single genus in which the functional queens vary, according to species, from " normal " winged (when virgin) to ergatoid or even dichthadiiform types. This arrangement has already been tacitly accepted by Wilson (1957), and it would be well to deal with the diagnostic characters (Wheeler, 1918: 219) one at a time.

Specialization of queen. The most primitive kind of queen (Africa, Brasil, Western Australia) has wings that are lost, presumably in the usual fashion, before the colony is founded, or at least before the queen joins an established colony. Queens of species such as S. steinheili , S. asper , and S. duchaussoyi are wingless and ergatoid in thoracic structure, but have 3 distinct ocelli and a pair of compound eyes. In imbecilis , the queen has undergone further specialization; the head is broadened and its sides rounded, the ocelli are reduced to one, and the compound eyes are reduced to minute vestiges; this ant is clearly on its way towards becoming a dichthadiiform, and it is important to note that the development of wings and pterothorax is not the only criterion on which the queens may be sorted.

Habits " hypogaeic " vs. " probably epigaeic. " Wheeler's use of this ethological character, even as stated, is obviously speculative. The meager evidence available fails to support his classification. I found S. steinheili travelling aboveground in full daylight during a raid on a nest of Stigmacros in Victoria, Australia, although the raiders used cracks in the soil for some parts of their trail (Wilson, 1958: 136). On the other hand, I collected a worker of S. turneri foraging under leaves in dark rain forest in northern Queensland. At the very least, the distinction between these two species and their respective subgenera on hypogaeic vs. epigaeic foraging habits must be considered as blurred. In fact, Wheeler's classification is based on the presence or absence of worker eyes, a trait that may no more reflect foraging habits than it does in the true army ants. By the same token, it is possible, even probable, that some of the species with blind workers really are hypogaeic in foraging habits.

Antennae 12 - merous vs. 11 - merous in worker and queen. This character was weak to begin with, because the workers of forms with winged / dealate queens can have either 12 or 11 segments, S. furcatus , though not very close to the Australian " Eusphinctus s. str., " has 11 segments in worker and queen. Now we have S. asper , which is very close to the Australian Eusphinctus s. str. but has 12 antennal segments instead of 11. As in Cerapachys , antennal segment number apparently has undergone independent reductions that make it a poor group character.

Pygidium notched vs. entire. Wheeler (1918: 219) noted that: the worker of E. cribratus Emery of New Guinea has an entire pygidium and belongs with the Australian species in Eusphinctus s. str., but the workers of the Indian species E. furcatus Emery and taylori Forel have a notched pygidium. Should future investigation show that the pygidial characters are correlated with other peculiarities or with different types of female, it may be advisable to restrict the subgenus Eusphinctus to the two Indian species and to suggest a new subgeneric name for the Australian and Papuan forms with 11 - jointed antennae. The emarginate pygidium itself is not a very impressive group character, since it is partly linked to size. " Zasphinctus " turneri has it in the worker, and " Nothosphinctus " queens have it, while workers do not. Also, emargination occurs to different degrees among the species that have it, and even the angle of view affects its distinctiveness.

The Indian species furcatus [68] has now been found to possess an ergatoid female with eyes modestly larger than the minute ones of its worker, although its overall body size hardly differs from that of the worker in the same colony. The differences in the proportions of the gastric segments between furcatus (fig. 100) and other Sphinctomyrmex seem not to have attracted much notice, though they weaken the separation between Sphinctomyrmex and Cerapachys . Now that we have the presumed males of furcatus , we note another difference in that this specimen has only 12 antennal segments, whereas all other known cerapachyine males have 13. The furcatus male also has the gastric segments proportioned about the same as in the worker, and its terminalia are fairly distinctive (although terminalia for related species are poorly known).

Forgetting about the emarginate pygidium, then, we might still make a fair case for separating furcatus and taylori into a genus Eusphinctus apart from both Sphinctomyrmex and Cerapachys , but it seems unwise to do this in a group so poorly known as Sphinctomyrmex , in which males have yet to be matched up to workers or queens in most species, and in which many species doubtless remain undescribed from any caste. It seems that problems in this group will best be solved by rearing live colonies to get the males in association with the female castes.

bionomics: Discussed previously under the tribe.

distribution: Sphinctomyrmex is best represented in numbers of species, and is decidedly more common, in Australia than in other parts of the world, but the genus also occurs in New Guinea, New Caledonia, and southern Asia.

At least 2, and probably more, species exist in west and central Africa, where the 2 were originally described from males, and 2 distinctly different, undescribed species are known in the worker caste, plus 1 undescribed form known from a winged queen. Elsewhere, Sphinctomyrmex is represented only by a single rare species from southeastern Brasil.