The November Spider of the Month (SOTM) is this juvenile horned bark spider (Caerostris sexcuspidata) in the orb-web spider family (Araneidae), photographed by Kyle Thomas in Magoebaskloof, Limpopo.
Regarding this find, Kyle said:
“This hot and dry spring has made subjects very difficult to find, even in these misty mountains. The cooler night walks as usual provided much better results. I managed to find a rather nice diversity of spiders. Among them was this very small C. sexcuspidata at only 3 mm in diameter. I am extremely happy with how this image turned out and really appreciate all the kind remarks.”
This species is also known as the common bark spider in Southern Africa, but “horned” bark spider is a more fitting name because of the “horns” on its back. They mostly have two horns, but can also have one, three, or even a “crown” of horns. These horns can also vary in shape and length. It’s not certain how many of these variations belong to the same species, or other similar but undescribed species.
They are cryptic spiders that hide on bark during the day. They sit very flat against the bark, with their legs pulled in, and rely on their leathery, bark-like texture for camouflage. Most species remove their web during the day before they go into hiding, but some of them, especially in dark forests, don’t remove their webs.
They build very large orb webs between vegetation, mostly trees. The largest orb web in the world belongs to Darwin’s bark spider (Caerostris darwini), found in Madagascar, and these webs often span rivers, with a bridge line of up to 25 metres long.
There are 18 recorded Caerostris species in the world, with four recorded species in South Africa. Most species occur in Africa and its surrounding islands, especially Madagascar. Only two species are found elsewhere, in Asia. C. sexcuspidatacan be found from Cameroon to Ethiopia and to South Africa, Seychelles, Comoros, and Madagascar.
This species (originally Aranea sexcuspidata) was described 231 years ago, in 1793, by Danish zoologist Johan Christian Fabricus. As far as species descriptions go, this is very long ago, and only 40 years after Carl Linnaeus’ Species Plantarum, which formalised binomial nomenclature as we know it today. This makes it our fifth oldest “native” spider species, after Argiope lobata (1772), Cyrtophora citricola (1775), Nephilingis cruentata (1775), and Pycnacantha tribulus (1781).
I have no idea what Caerostris means (if anyone knows, please enlighten us). The specific epithet sexcuspidata means six-pointed, from the Latin sexus, meaning six, and the Latin cuspidatus, meaning “having a cusp/tip/point”. I’m not sure if this refers to six “points” on the abdomen, or elsewhere.
This is Kyle’s third SOTM. Out of 173 people who voted, his photo received 81 (47%) votes. Congratulations, Kyle, and thanks for all the awesome photos!
