''Triaeris stenaspis'' is a species of

spider Spiders (order (biology), order Araneae) are air-breathing arthropods that have eight limbs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude spider silk, silk. They are the largest order of arachnids and ran ...

in the family

Oonopidae Oonopidae, also known as goblin spiders, is a family (biology), family of spiders consisting of over 1,600 described species in about 113 genus, genera worldwide, with total species diversity estimated at 2000 to 2500 species. The type genus of th ...

, with a pantropical distribution. It is also found in

Iran Iran, officially the Islamic Republic of Iran (IRI) and also known as Persia, is a country in West Asia. It borders Iraq to the west, Turkey, Azerbaijan, and Armenia to the northwest, the Caspian Sea to the north, Turkmenistan to the nort ...

and has been introduced into Europe. A very small spider, with a maximum body length of under , it has been shown to prey successfully on

springtail Springtails (class Collembola) form the largest of the three lineages of modern Hexapoda, hexapods that are no longer considered insects. Although the three lineages are sometimes grouped together in a class called Entognatha because they have in ...

s. Only females have ever been found, and the species may be

parthenogenetic Parthenogenesis (; from the Greek + ) is a natural form of asexual reproduction in which the embryo develops directly from an egg without need for fertilization. In animals, parthenogenesis means the development of an embryo from an unfertiliz ...

, being able to produce female offspring from unfertilized eggs.

Description

The male of the species is unknown. The female is generally pale orange or yellowish brown, with a body about long. Like most members of the family Oonopidae, ''T.stenaspis'' has only six eyes. Adults, but not immature stages, have hardened, darker plates or scuta on the abdomen. On the upper surface, the dorsal scutum covers most of the abdomen. On the lower surface, the ventral scutum is divided into two halves by the

epigastric furrow The anatomy of spiders includes many characteristics shared with other arachnids. These characteristics include bodies divided into two tagmata (sections or segments), eight jointed legs, no wings or antennae, the presence of chelicerae and pedi ...

, so that sources variously describe it as one or two scuta, making two or three scuta in total. A diagnostic character of the genus ''Triaeris'' is the long

patella The patella (: patellae or patellas), also known as the kneecap, is a flat, rounded triangular bone which articulates with the femur (thigh bone) and covers and protects the anterior articular surface of the knee joint. The patella is found in m ...

; the patella of the first leg of ''T.stenaspis'' is almost as long as the tibia. In adults, the first leg has three pairs of spines on the ventral surface of the patella and five pairs on ventral surface of the tibia. Immatures have fewer spines. The genitalia are complex, occupying most of the ventral scutum.

Taxonomy

The species was first described by

Eugène Simon Eugène Louis Simon (; 30 April 1848 – 17 November 1924) was a French naturalist who worked particularly on insects and spiders, but also on birds and plants. He is by far the most prolific spider Taxonomy (biology), taxonomist in history, ...

in 1891, based on a specimen collected in the West Indian island of Saint Vincent. It is the

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

of the genus. Simon also noted that it had been found in Venezuela. The generic name ''Triaeris'' is derived from the

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

word ', meaning "three rows of oars" (as in

trireme A trireme ( ; ; cf. ) was an ancient navies and vessels, ancient vessel and a type of galley that was used by the ancient maritime civilizations of the Mediterranean Sea, especially the Phoenicians, ancient Greece, ancient Greeks and ancient R ...

); the specific epithet ''stenaspis'' here means "with a narrow carapace".

Distribution and habitat

''Triaeris stenapis'' has a wide distribution in tropical and subtropical areas of the world, including the Americas from the southern United States south to Argentina, central Africa and Madagascar, Taiwan, Queensland in Australia, and isolated islands such as the Galápagos, Hawaii, the Marquesas and the Cook Islands. In Europe, it has been introduced in heated greenhouses, including those in Finland, Britain, France, Belgium, the Czech Republic and Slovakia. In larger European cities that are warmer than the surrounding countryside, it has also been found in more natural habitats. The species is primarily an inhabitant of

leaf litter Plant litter (also leaf litter, tree litter, soil litter, litterfall, or duff) is dead plant material (such as leaves, bark, needles, twigs, and cladodes) that has fallen to the ground. This detritus or dead organic material and its constituen ...

; most collections of the genus ''Triaeris'' have been obtained by sifting leaf litter.

Prey

There have been few studies of the prey taken by ''Triaeris stenaspis'' in the wild;

s and

ant Ants are Eusociality, eusocial insects of the Family (biology), family Formicidae and, along with the related wasps and bees, belong to the Taxonomy (biology), order Hymenoptera. Ants evolved from Vespoidea, vespoid wasp ancestors in the Cre ...

s have been suggested as possible prey. In a laboratory study conducted on ''T.stenaspis'' using spiders and potential prey collected in the botanical garden of the

Masaryk University Masaryk University (MU) (; ) is the second largest university in the Czech Republic, a member of the Compostela Group and the Utrecht Network. Founded in 1919 in Brno, it now consists of ten faculties and 35,115 students. It is named after To ...

in the Czech Republic, it was found that springtails were strongly preferred. They were captured by a grasp-and-hold strategy. Prey was bitten behind the head and was rapidly immobilized, although about 10% of the prey were able to jump once, during which time the spider held on. The authors of the study suggest that ''T.stenaspis'' may be a specialist predator on springtails.

Parthenogenesis

As males have never been found, the species is thought to be

, although this has only been demonstrated in spiders kept under laboratory conditions. Individuals were reared from eggs and kept alive on a diet of

s until they died. After hatching, they passed through three juvenile stages (instars), each lasting about a month and followed by a

moult In biology, moulting (British English), or molting (American English), also known as sloughing, shedding, or in many invertebrates, ecdysis, is a process by which an animal casts off parts of its body to serve some beneficial purpose, either at ...

during which they increased in size. Adults lived on average about six months. All the spiders were female and, although kept in isolation, laid fertile eggs that developed into females, thus demonstrating parthenogenesis (more specifically,

thelytoky Thelytoky (from the Ancient Greek, Greek θῆλυς ''thēlys'' "female" and τόκος ''tókos'' "birth") is a type of parthenogenesis and is the absence of mating and subsequent production of all female diploid offspring as for example in aph ...

References

{{Taxonbar, from=Q2182443 Oonopidae Pantropical spiders Spiders described in 1891 Spiders of Africa Spiders of Asia Spiders of Australia Spiders of Central America Spiders of Europe Spiders of North America Spiders of South America Unisexual animals