07 March 2020
Invertebrates of Kalahari (Series 2) — Arachnids I (Spiders)
Printer: Southern Colour Print, New Zealand
Artist: Baboloki Somolekae
Graphic Designer: Monkgogi Samson
Process: CMYK – Four Colour Process
Sheet: 2 x 12 panes with gutter
Stamp Size: 45mm x 38mm x 38mm
Souvenir Sheet: Die-cut miniature sheet 120mm x 105mm
FDC: 220mm x 140mm
Denominations: 0.50t, P1.00, P2.00, P5.00, P7.00, P10.00
Material: NovaStamp Non-Phosphor Gummed 105gsm
Date of Issue: 7th March 2020
Period of sale: 2 years
This is the 2nd stamp issue in the Invertebrates of the Kalahari Stamp series. The stamps showcase the 6 different spiders found in the Kgalagadi area. Spiders are commonly known as “Segokgo” in Setswana language.
1. Ceratogyrus darlingi
Commonly known as East African Horned Baboon spiders, or African rear-horned baboon spider, this species belongs to the spider family Theraphosidae. This spider is native to southern Africa, being distributed across Botswana, Mozambique, Namibia, Zimbabwe and South Africa. They are common in the Central Kalahari Game Reserve.
They reach a body length of about 130 mm and are ash gray, mud-brown to black. The carapace features a black foveal horn. Females and juveniles live in silk-lined burrows usually made in lightly wooded grassland and open clearings, sparsely covered with grass. The opening of the burrow is frequently found in an open area near grass tufts. The diameter of the entrances varies from 20-25 mm and the depth 240-400 mm. Some burrows are wider at the surface but taper inwards. Most burrows are J-shaped but shapes vary depending on the pre-existing cavities. Food is usually pulled in and eaten inside the burrow. Molting also occurs inside the burrow.
Although they can give a very painful bite that can last for a number of hours, their bites are not fatal.
2. Stegodyphus domicola
Commonly known as African social spider (as well as velvet spiders), this species belongs to the spider family Eresidae. It is native to Southern Africa (specifically Angola, Botswana, Mozambique, Namibia, Zimbabwe and South Africa). Individuals live in large family groups, or colonies, in spectacular silken nests with tunnels and broad chambers, surrounded by capture webs that can be very large.
This is one of the very few species of spiders that are social. The spiders in the nest share the tasks of nest building and maintenance, prey capture, and care for the young. Only some females mate and lay eggs but all females, including the unmated “virgin spiders”, share in childcare duties. When the nest becomes too hot inside, the females take the egg sacs out of the broad chamber and hung them in the shade below the nest. When the young emerge from the eggsacs, they are fed by the females by regurgitation. The females eventually sacrifice themselves for the young by allowing the young to feed on them while alive, a behavior called matriphagy.
3. Seothyra fasciata
Commonly known as buckspoor spiders, buck spoor spiders or just spoor spiders, this species belongs to a sand-dwelling burrowing genus of spiders in the family Eresidae. This genus is endemic to the arid, sandy flats and grassland areas of southern Africa. They construct burrow retreat-webs consisting of a burrow lined with silk. The entrance is covered with a lobed silk flap that serves as a signal web. The upper part of the silk flap is covered with sand and resembles a hoofprint (spoor of a buck) in the sand. These spiders are sexually dimorphic. The males imitate velvet ants in their appearance and habits, while the females live in and hunt from their characteristic burrows.
The female spends her whole life in the burrow, but may relocate it when damaged or in response to extreme climatic conditions. The female is a sit-and-wait predator that senses surface vibration using a single thread in the burrow. She takes an upside down position under the silk flap (sheet web that covers the burrow entrance) and will first venture to the underside of the sheet web before she strikes and eventually disentangle her prey. Prey are usually ants, and their remnants are left at the bottom of the burrow. A daily food intake, which equals 1% of their body mass, is sufficient to sustain their slow metabolism.
4. Kima africana
Kima spiders are free-living spiders that move around on the vegetation. They belong to the jumping spider family Salticidae. Jumping spiders have large front eyes and very good eyesight. This species mimics the large Camponotus ants both in morphology and behavior, hence its common name Ant mimic spider.
Morphological adaptations to resemble ants include the elongated carapace with a median depression, modified shape of the abdomen, long legs, and the yellow-grey setae that cover the entire body. They generally move slowly and move their legs up and down to imitate the antenna movements of ants – a behavior that is typical of many salticid ant mimics.
5. Trichonephila senegalensis
Females are much larger than males. Females have a bright yellow to orange red sternum and extremely long banded legs clothed with silver hairs. They make a large orb-web, varying from 40-50 cm in diameter, of strong yellow silk, in the open or amongst trees. The spiders make use of the same web over a long period of time, replacing only the viscid lines. In older spiders the web is only half a circle, while in the younger individuals the orb is more complete. The female hangs in the center of the web and the much smaller males on the edge. These spiders are common during the summer months.
6. Ammoxenus psammodronus
Commonly known as the sand-diving spiders or termite-eating spiders. This species belongs to the spider family Ammoxenidae. All species of the genus Ammoxenus specialize in feeding exclusively on termites, a fact that makes the species unique among spiders (spiders in general feed on a broad range of prey species).
Their chelicerae are modified, with the main portion curving downwards and covered with numerous obtuse spines that help to dive into the soil. The legs in dead specimens curl up. The color pattern varies greatly between specimens of the same species. Some specimens, especially males, have a rich velvety reddish color.
Ammoxenus species are agile, free-running, ground-living spiders. They have the ability to dive headfirst into the sand by using their modified chelicerae while holding their legs close to their bodies, hence the common name sand divers. They are usually found in areas where harvester termites are active. During inactive periods they are found concealed in a sac-like retreat in the soil dumps of the harvester termites, or buried in the sand. The egg sac is a cup-shaped cocoon buried in the sand of the termite soil dump.
Mr. Baoloki Somolekae is a young artist born in Molepolole. He recently graduated from University of Botswana, with a Bachelor in Industrial Design. This is his 3rd set of stamps, and his 2nd set in the Invertebrates of Kalahari stamp series, with Insects being the 1st.
Born in Palapye, graduated with a B-Tech Degree in Graphic Design from the Cape Peninsula University of Technology, South Africa. He has been working as a Visual and Brand Communications designer for over 10 years, designing for corporates, non-profits, academia, governments and the private sector. This is his 3rd stamp issue.