Nine new species of Crab Spiders from Africa.

Crab Spiders of the genus Mystaria are found in Africa from Guinea in the west to Ethiopia in the east and south to Cape Province in South Africa. They are ambush hunters, lying in wait for prey on plants in a wide variety of environments, from forest canopies to grasses to coastal wetlands.

In a paper published in the journal Zootaxa on 15 October 2014, Allet Honibull Lewis of the Department of Zoology & Entomology at the University of Pretoria and Ansie Dippenaar-Schoeman of the Department of Zoology & Entomology at the University of Pretoria and the ARC-Plant Protection Research Institute describe nine new species of Crab Spiders from across Africa, eight of them in the genus Mystaria, and one in a new genus, Leroya, which lives exclusively in the rainforest canopy. In addition they contend that the previously described genus Paramystaria is invalid, and move six species from this genus to Mystaria, and one species from Mystaria to Leroya.

The first new species described is named Mystaria budongo, in reference to the Budongo Forest of Uganda, where it was most abundant. The species is described from sixteen specimens collected in Rwanda, Democratic Republic of Congo, Kenya and Uganda. All of the known specimens are male. Mystaria budongo is 2.7-2.9 mm in length, and has a pear-shaped carapace with an orange-yellow median band and horizontal black and brown bands. The legs are yellow. The species lives in the forest canopy.

Mystaria budongo male from Rwanda, Ibanda Makera (dorsal view). Honibull Lewis & Dippenaar-Schoeman (2014).

The second new species described is named Mystaria irmatrix, in honour of Allet Honibull Lewis’ mother. The species is described from 19 specimens collected in Mozambique and South Africa, including members of both sexes and juveniles. Females were 3.15-4.14 mm in length and either orange with black markings or black with orange markings. Males were smaller, at 2.50-3.13 mm in length, and orange or brown with black markings. The species was found living in trees in coastal woodlands and grasslands, along rivers and around sand dunes

Mystaria irmatrix female from Mozambique, Marracuene in antero-dorsal view. Honibull Lewis & Dippenaar-Schoeman (2014).

The third new species is named Mystaria lindaicapensis, honouring Linda Wiese who collected the first specimen, and referring to the Cape region of South Africa where it is found (in both Eastern and Western Cape Provinces). The species is described from one female and two male specimens. The female is 3.9 mm in length and brown with orange markings. The males are 2.78 and 2.87 mm in length, and blackish brown with orange-red markings. Two of the specimens were collected from a garden the third from woodland.

Mystaria lindaicapensis female from South Africa, Jeffreys Bay in antero-dorsal view. Honibull Lewis & Dippenaar-Schoeman (2014).

The fourth new species described is named Mystaria mnyama, meaning ‘black’ in Zulu, a reference to the colouration of areas on the face and around the eyes. The species is described from one male and one female specimen, collected from grass and shrubs in Tembe Elephant Park in KwaZulu-Natal Province, South Africa. The female is 2.64 mm in length and copper-red in colour with dark facial markings and a lighter abdomen with two dark spots. The male is 2.29 mm in length with a dark copper-black body with lighter markings.

Mystaria mnyama female from South Africa, Tembe Elephant Parkinantero-dorsal view. Honibull Lewis & Dippenaar-Schoeman (2014).

The fifth new species described is named Mystaria oreadae, in reference to the Oreads (Mountain Nymphs) of Greek mythology, as the species was found exclusively in mountainous regions. The species is described from four female specimens, three from Nord Province in Rwanda and one from Orientale Region in the Democratic Republic of Congo. The specimens are 2.74-3.53 mm in length, red to orange copper with lighter or darker markings and a pale carapace.

Mystaria oreadae female from Rwanda, Rwankuba in antero-dorsal view. Honibull Lewis & Dippenaar-Schoeman (2014).

The sixth new species is named Mystaria savannensis, meaning ‘Savanah-dweller’. The species is named from 111 specimens collected in Zambia, Botswana, South Africa and Zimbabwe, including males, females and juveniles. The females are 3.15-5.08 mm in length and orange red or dark brown with a pale abdomen with a darker central stripe. The males are 2.50-3.27 mm in length and copper brown in colour with a darker abdomen. The species was found in trees, shrubs and leaf litter across a wide area of southeast Africa.

Mystaria savannensis female from South Africa, Soutpansberg in antero- dorsal views. Honibull Lewis & Dippenaar-Schoeman (2014).

The seventh new species is named Mystaria soleil, meaning ‘Sun’ in French, due to its bright yellow colour. The species is described from 42 specimens collected in Masindi District, Uganda and Western Province, Kenya. The females are 3.13-3.48 mm in length, the males 2.46-2.70 mm, females are pale brown with darker bands and spots and yellow legs, males also have a yellow abdomen.

Mystaria soleil female from Kenya, Kakamega in dorsal view. Honibull Lewis & Dippenaar-Schoeman (2014).

The eighth new species described is named Mystarias takesbyi, in honour of Eduard Stakesby, the husband of Allet Honibull Lewis. The species is described from 15 specimens from Ghana, the Democratic Republic of Congo, Gabon, Liberia, Kenya, Rwanda, Tanzania and Uganda. Females are 2.72-4.07 mm in length and copper-red, orange or brown in colour, usually with a darker central band and lighter patches. Males are 2.34–2.76 mm in length and a uniform dark copper red, with a lighter abdomen with faint black marks. The species was found primarily in the rainforest canopy, but was also found in leaf litter.

Mystaria stakesbyi female from Ghana, Legonin dorsal view. Honibull Lewis & Dippenaar-Schoeman (2014).

The final new species is placed in a new genus, Leroya, named in honour of John and Astri Leroy; John Leroy collected a specimen of Mystaria unicolor, at Rwankwi in the Belgian Congo (now the Democratic Rebulic of Congo) in 1951, when he was six years old, which is one of the specimens used to re-assign this species to the new genus (becoming Leroya unicolor). It is given the specific name Leroya silva, which means forest in Latin. The species is described from nine specimens from the Democratic Republic of Congo, Rwanda and Uganda. Females are 3.89-4.22 mm in length and copper brown in colour with a metallic sheen. The males are 3.04–3.92 mm in length and copper or blackish-turquoise in colour, also with a metallic sheen. The species was found exclusively in the rainforest canopy.

Leroya silva from the Democratic Republic of Congo, Mayombe, male in dorsal view. Honibull Lewis & Dippenaar-Schoeman (2014).

See also…

How an invasive Grass species makes American Toads more vulnerable to Wolf Spiders. 
Invasive plants can significantly modify local habitats, particularly if they lack herbivores in the environments they are colonising, by both...

The subsocial lifestyle of an Australian Crab Spider.

Sociality is rare in Spiders, which are by nature solitary and aggressive. However it is known to have evolved...

A new species of blind Cave Spider from Keloğlan Cave in Denizli Province, Turkey.

Cave Spiders (Nesticidae) are found across the Mediterranean Basin, as well as in the Canary Islands and parts of Asia. They are cave-dwelling...

Follow Sciency Thoughts on Facebook.

The subsocial lifestyle of an Australian Crab Spider.

Sociality is rare in Spiders, which are by nature solitary and aggressive. However it is known to have evolved separately several times in different Spider groups, and this occurrence is considered a good model for the understanding of the evolution of sociality across the animal kingdom, because it involves a switch in behaviour which is apparently strongly against the basic nature of Spiders. Social Spiders gain an advantage over non-social species in that they are able to hunt collectively, thereby often targeting larger prey, and mount a common defence against predators. However they also suffer disadvantages compared to other species, in the form of competition for resources within the nest. 

In the case of Spiders competition for mates can be an important evolutionary driver, as male Spiders are typically only capable of mating with a single female, and the evolution of sociality often comes via the ‘subsocial route’, wherein species go through a subsocial stage, with Spiders living communally during a period of extended maternal care, but dispersing prior to mating, and the switch from subsociality to full sociality (in which Spiders live communally for their entire lives) being also accompanied by a switch from outbreeding (mating between unrelated Spiders) to inbreeding (mating between related Spiders, within the same nest), a switch that tends to trigger other evolutionary changes.

Sociality is known to have arisen separately in at least eight groups of Spiders. The majority of these are web-builders, with the advantages of larger, communally built webs, that are capable of netting larger prey, seems to be important in the development of sociality. However it is also found in two groups of non-web-building Spiders, Huntsman Spiders (Sparassidae) and Crab Spiders (Thomisidae). In both cases this development has been found only in Australia, a continent whose long isolation and harsh climate has led to novel innovations in a wide variety of organisms. 

The social Huntsman Spiders were formerly placed in two genera, Delena and Eodelena, however a recent molecular study of the group has revealed that all are more closely related than previously thought, and all are now placed within the single genus Delena. Three species of social Crab Spiders described to date, all of which have been placed within the genus Diaea.

In a paper published in the journal ZooKeys on 21 July 2014, Jasmin Ruch of the Department of Biological Sciences at Macquarie University and the Zoological Institute and Zoological Museum at Biocenter Grindel at the University of Hamburg, Torben Riehl, also of the Zoological Institute and Zoological Museum at Biocenter Grindel and Peter Michalik of the Zoological Institute and Museum at Ernst-Moritz-Arndt-University, describe the occurrence of subsocial behaviour in a fourth species of Australian Crab Spider, Xysticus bimaculatus from southern Queensland. Xysticus bimaculatus was first described in 1867, but its behaviour has not been studied until now.

Male and female Xysticus bimaculatus. Scale bar is 1 cm. Ruch et al. (2014).

Ruch et al. found that Xysticus bimaculatus builds social nests containing multiple females and their young. The nests were built from leaves in broadleaved forests around Brisbane (all species of Diaea nest exclusively in Eucalyptus trees, and none occur as far north as Brisbane), with the most used tree being the Blackwood (Acacia melanoxylon), which is also the most abundant tree in the area, though the Spiders seemed quite willing to use any tree. The nests were constructed from leaves, with the spiders inhabiting old, brown leaves at the centre of the nest, but continuously adding new green leaves to the outside. 

The Spiders attach leaves with silk to construct a typical nest. Scale bar is 1 cm. Ruch et al. (2014).

Most nests contained a single female and her young, however nests in which multiple adults were found caring for a single brood, and nests in which there was more than one separate brood were also found. The Spiders have an annual life-cycle, and all the young within a nest appeared to be the same age. The likelihood of the females being present with the young decreased as the Spiderlings grew, though whether this was due to matrophagy (the eating of the mother by the young, common in Spiders) or some other factor was unclear.

Prey items found within the nests included mainly Beetles and Ants, however Wasps, Caterpillars and Flies were apparently also consumed. Wooly Scale Insects and Cockroaches were found living in some nests as apparent commensals (species living in the nest of another without harming or benefiting the host), and other species of Spider (potential predators of young Spiderlings) were also found in some nests.

See also…

 A new species of blind Cave Spider from Keloğlan Cave in Denizli Province, Turkey.

Cave Spiders (Nesticidae) are found across the Mediterranean Basin, as well as in the Canary Islands...

 A giant Spider from the Middle Jurassic Daohugou Biota.

In 2011 Paul Seldon of the College of Life Sciences at Capital Normal University in Beijing, the Paleontological Institute and Department of Geology at the University of Kansas and the Natural History Museum in London, along with ChungKun Shih and Dong Ren, also of the College of Life Sciences at Capital Normal University, described a large female Spider...

 The repeated evolution of sociality in a genus of Eresid Spiders.

Social Spiders are unusual in that the females form colonies of hundreds to thousands of individuals, which cooperate in the building of webs, capture of prey, defence of the colony and raising of young. Unlike...

Follow Sciency Thoughts on Facebook.