spider systematics

With their astonishingly precise spiral webs, orb-weaving spiders are the arachnid analogy of first-class mathematicians, note the researchers behind the study

Despite being considered as one of the best-studied spiders in the Palearctic, the orb-weaver spiders (family Araneidae) remain poorly known in the central parts of the ecozone. To bridge the knowledge gaps, an international research team of researchers took to the Caucasus, Middle East and Central Asia to study two of those genera: Araniella and Neoscona.

As a result, in their article, recently published in the open-access scientific journal ZooKeys, arachnologists Alireza Zamani (University of Turku, Finland), Yuri M. Marusik (Institute for Biological Problems of the North RAS, Russia) and Anna Šestáková (The Western Slovakian Museum, Slovakia) describe three new-to-science species, where one: Araniella villanii – carries the name of the flamboyant French mathematician and spider aficionado Cédric Villani, who has been dubbed the “Lady Gaga of Mathematics”. Even if unknown until now, the species turned out to have a wide distribution, ranging from south-western Iran to eastern Kazakhstan and northern India.

A female specimen of the newly described orb-weaver species *Araniella villanii* on its web (Kazakhstan)
Photo by Alireza Zamani

“It’s a well-known fact within the arachnological community that spiders are masters of mathematics and architecture. Orb-web spiders, in particular, tend to build beautiful and architecturally aesthetic webs, some of which are formed in spirals in line with the repetitive pattern of the golden ratio,”
explains lead author of the study Alireza Zamani.

The web of the garden orb-web spider Araneus diadematus, for example, usually has 25 to 30 radial threads forming an astonishingly precise angle of about 15°, which the spider carefully measures using its front legs. According to scientific observations, if the front legs are removed, the regularity of the angles between adjacent radial threads is impaired.

For these and many other reasons, spiders must have been an inspiration for mathematicians like Cédric Villani, who has publicly shown a mysterious love for these arachnids. Awarded the Fields Medal (some say it is the Mathematics equivalent of the Nobel Prize) in 2010 and having served as the director of Sorbonne University‘s Institut Henri Poincaré from 2009 to 2017, the Frenchman’s love for spiders is quite evident, thanks to the constant presence of a spider brooch on his lapel. Although he has never explained the reason behind his appreciation of these eight-legged wonders, now he has a real, even scientifically sound connection to them in the real world.

Apart from Araniella villanii, whose scientific name honours the prominent scientist and recognises his love for spiders, the other two newly-described species also have a story behind their names. One of them: Neoscona isatis, discovered in central Iran, was named after the historical name of its type locality; and Araniella mithra, known from north-western, central and south-western Iran, was named after Mithra, the god of light in the ancient Indo-Iranian mythology.

Curiously, spiders in the genus Araniella are green in colour due to certain bile pigments (biliverdin) that make them very difficult to spot in their natural habitat, as they live mostly on leaves.

French mathematician and spider aficionado Cédric Villani (left) with lead author and discoverer of the three new-to-science orb-weaver spiders Alireza Zamani (right) in Iran (2015)

“I met Mr. Villani in May 2015 at University of Tehran, where he was an invited speaker. We got to briefly talk about our shared interest in spiders, and I had the opportunity to present him an Iranian wolf spider as a souvenir!”
recalls Zamani.

“It’s important to note that, with the efforts of taxonomists, new species are being discovered and described with an average rate of 18,000 species per year, but simultaneously both known and undescribed species go extinct due to human activities, with the current rate being within or even higher than the range of the newly described ones. A first step towards conservation of biodiversity includes taxonomic research to document species and to define hotspots of species diversity in order to protect such carefully selected habitats,”
he points out.

A female specimen of the newly described orb-weaver species Araniella villanii in its natural habitat (Kazakhstan)
Photo by Anatoliy Ozernoy

“However, with the current situation of low funding for taxonomic research, the number of students doing taxonomic research is in severe decline and the current average ‘shelf life’ (between discovery and description) of a new species remains at about 21 years. Araniella villanii is a great example of how much we don’t know about our biodiversity.”

Despite being discovered all the time, new species mostly have very restricted ranges and are only known from a few nearby localities. Orb-weaver spiders have very good dispersal abilities and it is relatively uncommon to detect new species of them.

“Araniella villanii is known from a few localities in southwestern Iran, eastern Kazakhstan and northern India, a distribution range covering at least ten countries, and yet the species was unknown to science until now. I think that the message that this particular discovery implies is that while there are such widely-distributed undescribed species out there, we need more and more taxonomic research, both in the field and in the natural history museum collections, which house a considerable number of undescribed species, in order to preserve the remaining biodiversity on earth, before it’s too late”.

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Original source:

Zamani A, Marusik YM, Šestáková A (2020) On Araniella and Neoscona (Araneae, Araneidae) of the Caucasus, Middle East and Central Asia. ZooKeys 906: 13-40. https://doi.org/10.3897/zookeys.906.47978

A new to science species of tarantula with a peculiar horn-like protuberance sticking out of its back was recently identified from Angola, a largely underexplored country located at the intersection of several Afrotropical ecoregions.

Collected as part of the National Geographic Okavango Wilderness Project, which aims to uncover the undersampled biodiversity in the entire Okavango catchment of Angola, Namibia and Botswana, thereby paving the way for sustainable conservation in the area, the new arachnid is described in a paper published in the open-access journal African Invertebrates by the team of Drs John Midgley and Ian Engelbrecht.

Although the new spider (Ceratogyrus attonitifer sp.n.) belongs to a group known as horned baboon spiders, the peculiar protuberance is not present in all of these species. Moreover, in the other species – where it is – the structure is completely sclerotised, whereas the Angolan specimens demonstrate a soft and characteristically longer ‘horn’. The function of the curious structure remains unknown.

The new tarantula’s extraordinary morphology has also prompted its species name: C. attonitifer, which is derived from the Latin root attonit– (“astonishment” or “fascination”), and the suffix –fer (“bearer of” or “carrier”). It refers to the astonishment of the authors upon the discovery of the remarkable species.

“No other spider in the world possesses a similar foveal protuberance,” comment the authors of the paper.

*Individual of the newly described species in defensive posture in its natural habitat. Photo by Kostadine Luchansky.*

During a series of surveys between 2015 and 2016, the researchers collected several female specimens from the miombo forests of central Angola. To find them, the team would normally spend the day locating burrows, often hidden among grass tufts, but sometimes found in open sand, and excavate specimens during the night. Interestingly, whenever the researchers placed an object in the burrow, the spiders were quick and eager to attack it.

The indigenous people in the region provided additional information about the biology and lifestyle of the baboon spider. While undescribed and unknown to the experts until very recently, the arachnid has long been going by the name “chandachuly” among the local tribes. Thanks to their reports, information about the animal’s behaviour could also be noted. The tarantula tends to prey on insects and the females can be seen enlarging already existing burrows rather than digging their own. Also, the venom of the newly described species is said to not be dangerous to humans, even though there have been some fatalities caused by infected bites gone untreated due to poor medical access.

In conclusion, the researchers note that the discovery of the novel baboon spider from Angola does not only extend substantially the known distributional range of the genus, but can also serve as further evidence of the hugely unreported endemic fauna of the country:

“The general paucity of biodiversity data for Angola is clearly illustrated by this example with theraphosid spiders, highlighting the importance of collecting specimens in biodiversity frontiers.”

Apart from the described species, the survey produced specimens of two other potentially new to science species and range expansions for other genera. However, the available material is so far insufficient to formally diagnose and describe them.

*The newly described baboon spider species (Ceratogyrus attonitifer), showing the peculiar soft and elongated horn-like protuberance sticking out of its back. Photo by Dr Ian Enelbrecht.*

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Original source:

Midgley JM, Engelbrecht I (2019) New collection records for Theraphosidae (Araneae, Mygalomorphae) in Angola, with the description of a remarkable new species of Ceratogyrus. African Invertebrates 60(1): 1-13. https://doi.org/10.3897/afrinvertebr.60.32141

Tag: spider systematics

French mathematician and spider aficionado Cédric Villani honoured with a new orb-weaver

With their astonishingly precise spiral webs, orb-weaving spiders are the arachnid analogy of first-class mathematicians, note the researchers behind the study

New tarantula species from Angola distinct with a one-of-a-kind ‘horn’ on its back

“No other spider in the world possesses a similar foveal protuberance,” comment the authors of the paper.

“The general paucity of biodiversity data for Angola is clearly illustrated by this example with theraphosid spiders, highlighting the importance of collecting specimens in biodiversity frontiers.”