Anochetus siphneus

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Anochetus siphneus
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Ponerinae
Tribe: Ponerini
Genus: Anochetus
Species: A. siphneus
Binomial name
Anochetus siphneus
Brown, 1978

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Specimen Labels

So far as known, Anochetus siphneus is restricted to the West African forest belt, where it is found in the leaf litter or humus of the forest floor, and in rotten wood on the ground (Brown 1978).

Identification

Brown (1978) - Formerly, I had thought this species might be the same as Anochetus jonesi, but a direct comparison of type material shows that jonesi is larger, has relatively larger eyes, and has a blunter, more narrowly rounded petiolar apex as seen from the side. Perhaps A. siphneus has been confused in the past also with Anochetus talpa; I suspect that the A. talpa recorded by Santschi 1914b: 331 from Ibadan, Nigeria, may really be A. siphneus, but I have not studied Santschi's specimen. A. talpa (syntypes in Musee d'Histoire Naturelle Genève) is likewise a very small yellow species with dot-like eyes of perhaps 7 facets, but the petiolar node is only feebly tapered apicad as seen from the side, and its summit is considerably more broadly rounded even than in A. jonesii.

A. siphneus is perhaps most closely related to Anochetus grandidieri and allies, but within this group, ties are obscure. It differs from Anochetus punctaticeps, which is similar in color, by its smaller eyes, slightly larger body size, narrow transverse mesonotal disc, emarginate nodal apex, and by the more abundant erect hairs on the gastric dorsum.

Keys including this Species

Distribution

Known from Ivory Coast, Nigeria and Ghana.

Distribution based on Regional Taxon Lists

Afrotropical Region: Ethiopia, Ivory Coast (type locality).


Distribution based on AntMaps

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Distribution based on AntWeb specimens

Check data from AntWeb

Biology

Not much is known about the the biology of Anochetus siphneus but we can presume that its biology is similar to other Anochetus species. The following account of Anochetus biology is modified from Brown (1968):

Habitat. The places where Anochetus live are varied. Where they penetrate into the temperate zone, most species excavate nests in the earth. Occasionally the nest is dug under a covering rock. In the tropics, many nests are also dug in the soil, but in moist forested areas, a common site is the soil beneath a rotting log or other large mass of rotting wood, with extensions of the nest into the log itself. Another frequent nesting site in tropical forest is in the humus and leaf litter at the base of large trees, particularly between buttress roots. Anochetus species of medium or small size often nest in small pieces of rotting wood or bark, or even small rotting twigs or seeds and nuts lying in or on the forest litter. Some species tend to choose more arboreal nest sites.

Diet. Foraging for living animal prey takes place on the soil surface, within the soil-humus-log mold matrix, or on the trunks, branches and foliage of trees and plants wherever these are available. Fragmentary evidence indicates that most epigaeically foraging tropical Anochetus tend to do their foraging at dusk, at night, or during dawn hours. I found Anochetus africanus walking on tree trunks only at night in the Ivory Coast. Some species, particularly those with red heads or other aposematic coloration, apparently forage in the open more during the day. No systematic comparative study has yet been made of foraging hours for different species.

The food of Anochetus consists principally of living arthropods caught and killed or incapacitated by the ants. The smaller and more delicate species Anochetus inermis has been observed by me in a laboratory nest. The colony came from a piece of rotten wood from the floor of a wet ravine near Bucay in western Ecuador. The colony was fed with small tenebrionid beetle larvae (Tribolium castaneum), comparable in size to the A. inermis workers, and the latter attacked the prey with their mandibles in the familiar snapping manner, but very cautiously and nervously, with stealthy approach, extremely rapid strike, and instant recoil-retreat. After several attacks of this kind, with intervening periods of waiting, during which the beetle larvae fled, rested, or writhed about in distress, an ant would finally attack with its mandibles and hold them closed on the prey for long enough to deliver a quick sting in the intersegmental membrane. After this, the prey appeared to be paralyzed, or at least subdued, and sooner or later was carried off by the ant to the nest, and eventually placed on an ant larva.

Frequent delays and excursions before the prey are finally immobilized and brought to the ant larvae in the nest may well have the function of allowing time for protective allomones of the prey to dissipate. Many tenebrionid adults, including Tribofium, possess potent quinonoid defensive allomones, but the larva is not known to possess quinones in this genus.

Nuptial flight. Although males of different species of Anochetus are commonly taken at light, other species are not. Stewart and Jarmila Peck gave me Malaise trap samples taken in western Ecuador that contained males of several species, but Malaise traps capture both day- and night-flying insects.

Defense. When a nest of any of the larger Anochetus species is breached, some of the workers immediately hide beneath leaves or other objects, while other workers rush about with open jaws, which they snap at foreign objects, or even at leaves and twigs, with an audible tick. On human skin or clothing, a worker will snap her jaws and hold fast to the surface with them, at the same time quickly bringing her gaster around to sting. The sting is long and strong, and to me the effect is shocking and quickly painful.

Most of the smaller and medium-sized Anochetus species feign death when disturbed, crouching flat against the surface, or rolling themselves into a ball and remaining still, often for a minute or more. Only when held do they sting. Their stings can be felt in most cases, but the effect is usually trifling.

Castes

Queen and male unknown.

Nomenclature

The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.

  • siphneus. Anochetus siphneus Brown, 1978c: 608, figs. 11, 19 (w.) IVORY COAST.

Description

Worker

Holotype, worker: TL 4.4, HL 1.12, HW 0.96, ML 0.52, WL 1.27, scape L 0.84, eye L 0.06 mm; CI 86, MI 46.

Paratypes, 3 workers: TL 4.0-4.5, HL 1.04-1.14, HW 0.92-1.00, ML 0.50-0.55, WL 1.24-1.35, scape L 0.80-0.86, eye L 0.06-0.10 mm; CI 86-91, MI 46-49.

Medium yellow; middle of dorsum of head slightly darker.

A small member of the grandidieri group with eyes reduced to dots of only about 7-15 facets, filling less than half the length of the orbital fossa. Scape fails to reach posterior border of occipital lobe by about the length of the first funicular segment (less in 2 paratypes); segments II, III and IV of funiculus longer than broad, subequal in length, together longer than I. Mandibles robust; preapical excision feeble, preapical angle low, rounded. Posteromedian impression wide and deep, shining, almost impunctate; nuchal carina in full-face view broadly V-shaped, with rounded apex.

Frontal striation continuing back onto the vertex for only a short distance beyond the midlength of the head, but replaced on the posterior disc of the vertex by dense, sometimes contiguous, coarse and fine punctures that surround the posteromedian impression; head otherwise smooth and shining.

Trunk compact, with the 2 sutures deeply impressed and longitudinally costulate at bottom. Pronotum with the usual fine margin around its anterior slope, paralleled by a narrow belt of fine, irregular rugulation or striation. Mesonotal disc narrow, straplike, about 3 times as broad as long. Dorsum of propodeum finely rugulose, weakly shining anteriad, otherwise opaque; discs of pro- and mesonotum and sides of trunk generally smooth and shining, as are also petiolar node and gastric dorsum. Node as in fig. 19; the paratypes are like this also except for the specimen from Gambari, Nigeria, which has the apical margin almost straight, with only a faintly concave tendency as seen from the front.

Pubescence short, appressed, moderately abundant on head, appendages and gaster, sparse and dilute on pronotum; the usual pair of erect hairs on the front of the pronotum, also 4 pairs of short, erect hairs straddling the cephalic midline: 2 pairs on frontal carinae, and 2 pairs on vertex. Gaster with up to about 25 coarse, stiff, pasteriorly-inclined, pointed hairs on the dorsum, 6-8 of these on first tergum.

Type Material

Holotype a single worker (Museum of Comparative Zoology) from the gallery forest of the Bandama River at the Station Scientifique de Lamto, south central Ivory Coast, in a berlesate of leaf litter and humus, W. H. Gotwald and R. Schaefer.

Paratypes (MCZC, The Natural History Museum) 3 workers: Ivory Coast, Banco Forest, near Abidjan, W. L. Brown; Ghana, Tafo, on mud under dead leaf, B. Bolton; Nigeria, Gambari, under fallen banana stem, B. Bolton.

References

  • Brown, W. L., Jr. 1978c. Contributions toward a reclassification of the Formicidae. Part VI. Ponerinae, tribe Ponerini, subtribe Odontomachiti. Section B. Genus Anochetus and bibliography. Stud. Entomol. 20: 549-638 (page 608, figs. 11, 19 worker described)