Thysanina Simon, 1910

Lyle, Robin & Haddad, Charles R., 2006, A revision of the Afrotropical tracheline sac spider genus Thysanina Simon, 1910 (Araneae: Corinnidae), African Invertebrates 47, pp. 95-116 : 97

Thysanina Simon, 1910

Type species: Thysanina serica Simon, 1910 .

Diagnosis: The genus Thysanina differs from the closely related Trachelas in several respects. Thysanina has a darkened eye region and slightly flattened yellow-brown carapace with a finely wrinkled surface, which appears smooth. The abdomen is creamy white to pale yellow, usually with a distinctive chevron marking ( Fig. 1 ). Trachelas often have a raised red-brown carapace with a number of small tubercles covering it, making the surface texture appear granular and rough ( Platnick & Shadab 1974; pers. observ.). The most obvious difference between the two genera is the variation in cusp presence, and the abdomen, which is grey in colour usually without a chevron marking in Trachelas . Thysanina males have ventral peg-like cups with pointed tips present on the tibiae, metatarsi and tarsi of the anterior legs, but cusps are absent in females. The occurrence of cusps is irregular in Afrotropical Trachelas ; some species have cusps in both sexes, others in males only, while some species have a total absence of cusps. When present, the cusps are usually smaller and more robust than those found in Thysanina , and have rounded tips (e.g. Platnick & Shadab 1974, figs 42, 43). The copulatory openings of the female epigyne are situated in the anterior half of the epigyne, and the embolus of the male palp typically originates distally or prolaterally on the tegulum, and may be coiled or straight.

Description: Small to medium sized spiders, 3.0– 5.5 mm in length; male more robustly built than female, with legs and abdomen thicker and more compact than female. Carapace slightly dorso-ventrally flattened, narrowest at ocular region, broader medially and rounded posteriorly ( Fig. 1 ); ocular region darkened with dark rings around eyes; anterior eye row slightly procurved, posterior eye row slightly recurved ( Figs 1 , 2 ); colouration yellow brown to bright orange; covered with fine setae ( Fig. 3 ). Chelicerae usually with three teeth on promargin, and two or three teeth on retromargin; endites 1.5 times longer than wide, sometimes with shallow longitudinal ridge along prolateral margin; straight on anterior and retrolateral margins, rounded on posterior margin; serrula indistinct; labium trapezoidal, slightly longer than wide. Sternum longer than broad, with smooth surface; long and short setae scattered across surface; colouration bright orange to brown, darker towards border. Legs with paired tarsal claws situated in between a dense claw tuft ( Fig. 4 ); cusps present in males and absent in females, found on tibia, metatarsus and tarsus ( Figs 5–8 ); cusps with a peg-like structure and pointed tips ( Fig. 9 ), situated within deep sockets ( Fig. 10 ); leg spines generally absent, but present in T. similis and T. transversa ; legs I to IV typically with grey bands; metatarsi III and IV of both sexes with distal ventral preening comb. Abdomen broader anteriorly and truncated posteriorly; integument with pale yellow to creamy white undertones, with a grey chevron marking usually present, except in T. similis females; chevron more distinct in males; dorsal scutum and inframamillary sclerite absent in both sexes. Female with paired copulatory openings in weakly sclerotised epigyne; epigyne structure varies greatly between species. Male palps vary greatly between species, with considerable variations in size and structure of tibial apophyses.

Figures

Fig. 1. General appearance of Thysanina serica Simon, 1910.

Figs 2–10. Scanning electron micrographs of male Thysanina transversa sp. n.: (2) eye region; (3) fine setae on smooth carapace surface; (4) paired tarsal claws covered by dense claw tuft; (5) metatarsus I with ventral cusps; (6) tibia I with ventral cusps; (7) metatarsus II with larger ventral cusps; (8) tarsus II with ventral cusps, located between dense setae; (9) structure of peg-like cusps found on the anterior legs; (10) cusp socket in integument.