Myrmarachne biseratensis Badcock, 1918

Yamasaki, Takeshi & Ahmad, Abdul Hamid, 2013, Taxonomic study of the genus Myrmarachne of Borneo (Araneae: Salticidae), Zootaxa 3710 (6), pp. 501-556 : 512-514

Myrmarachne biseratensis Badcock, 1918

( Figs 8 A–G, 9A–F)

Myrmarachne biseratensis Badcock, 1918: 312 , Fig. 10 ; Edmunds & Prószyński, 2003: 309, Figs 53–55.

Type material examined. Holotype male (BMNH), Biserat, [MALAY PENINSULA], Annandale & Robinson leg.

Non-type material examined. BORNEO: 1 male, UMS, Sabah, 20 III 2008, H. Takizawa leg.; 1 male, Kota Kinabalu Wetland Center, Sabah, 22 X 2010, T. Yamasaki leg.; 2 males and 1 female, Inobong, Crocker Range Park, Sabah, 16–17 XI 2010, T. Yamasaki leg.

Diagnosis. Constriction between cephalic and thoracic parts narrow and deep. In males, chelicera in dorsal view almost parallel-sided but in lateral view apically swollen; Basal half of fang strongly arched ( Fig. 8 C). In females, copulatory atria round; spermathecae elongate-oval; anterior part of sclerotised copulatory ducts complexly twisted; median pocket with anteromedian indentation present in front of epigastric furrow ( Figs 9 E–F).

Measurements (male/female). Carapace length 2.35–(2.85)/2.75, width 1.48–(1.90)/1.48. Abdomen length 2.15–2.50/2.25. Chelicera length 2.00–2.60. Sternum length 1.40–1.63/1.55. Width of eye row I 1.22–(1.36)/1.32; II 1.14–(1.26)/1.20; III 1.34–(1.50)/1.42. ALE–PLE 1.02–(1.10)/1.06; ALE–PME 0.46–0.50 (0.48)/0.48. Eye size: AME 0.41–0.44 (0.40)/0.43, ALE 0.19–0.21 (0.20)/0.20, PME 0.06–(0.08)/0.06, PLE 0.21–(0.24)/0.21.

Male ( Figs 8 A–G). Cephalic part almost flat or weakly convex dorsally. Constriction between cephalic and thoracic parts narrow and deep. Thoracic part convex dorsally, and sloping downward abruptly in posterior part. Chelicera in dorsal view nearly parallel-sided but in lateral view apically swollen, and with three or four prolateral and 13 to 14 small retrolateral teeth. Basal half of fang strongly arched. Sternum slender, slightly overlapped by coxa II and III. Abdomen oval with broad dorsal scutum that is incised on each lateral outline anteriorly.

Palp ( Figs 8 E–G). Tegulum very small and round, with strongly curved seminal reservoir in retrolateral part of tegulum. Embolus forming two small round coils; embolus coils occupying less than half of venter of cymbium. With palp in dorsal and ventral views curving of RTA not distinct, but in lateral view RTA strongly curved. Flange of RTA moderately developed.

Leg spination. Femur I md 1, pd 1, rd 1; tibia I pv 4–5, rv 4–5; metatarsus I pv 2, rv 2; femur II md 1, pd 1, rd 0–1; tibia II pv 2–3, rv 2–3; metatarsus II pv 2, rv 2; femur III pd 1, rd 0–1; femur IV md 0–1, pd 1, rd 1.

Coloration and pilosity. Coloration variable, especially in abdomen. Carapace entirely covered with white hairs; cephalic part black; thoracic part brown to black. Chelicera brown to dark brown. Maxilla, labium and sternum pale brown to dark brown. Coxa I dark brown or pale brown and coxae II, III and IV blackish brown or pale brown tinged with black. Abdomen covered with white hairs dorsally; scutum light brown to dark brown; integument except for scutum cream to dark grey.

Female ( Figs 9 A–F). Cephalic part almost flat dorsally. Constriction between cephalic and thoracic parts deep and narrow. Thoracic part strongly convex dorsally. Chelicera short (but relatively long compared with those of other females), with six prolateral and 13 retrolateral teeth. Sternum almost as in males. Abdomen oval with indistinct dorsal scutum that is not sclerotised.

Epigyne ( Figs 9 D–E). Copulatory atria containing openings round. Spermathecae elongate-oval; anterior part of sclerotised copulatory ducts twisted, extending from spermathecae to lower margins of copulatory atria. Median pocket with anteromedian indentation present in front of epigastric furrow.

Leg spination. Tibia I pv 5, rv 4; metatarsus I pv 2, rv 2; tibia II pv 3, rv 3; metatarsus II pv 2, rv 2. Coloration and pilosity. Carapace black to dark brown, covered with white short hairs overall. Chelicera brown. Maxilla, labium and sternum pale brown. Coxa I white; coxae II, III and IV tinged with black. Abdomen greyish brown, covered with white short hairs dorsally.

Distribution. Malay Peninsula (Badcock 1918), Penang island (Edmunds & Prószyński 2003), Borneo.

Remarks. The female of M. biseratensis is recorded for the first time in the present paper (but see the illustration of the female; Prószyński 2012). The species shows colour variation especially in the abdomen, light brown to dark brown. In the field the colour of the abdomen looks to be pink, red or black depending on individuals. The dentition of the male chelicera is very similar to that of M. opaca , but they are distinguished by the shapes of the chelicera and the fang; chelicera of M. biseratensis in dorsal view almost parallel-sided and basal half of fang strongly arched, but chelicera of M. opaca apically swollen and fang weakly curved.

Biology. The species is arboreal, and often occurs in gardens and forest edges. In colour pattern, the wet specimens which have a pale brown dorsal scutum (in the field the abdomen looks pale pink) resemble Polyrhachis bicolor F. Smith , and the individuals which have dark red abdomen resemble P. armata Le Guillou or P. abdominalis F. Smith. The varieties of M. biseratensis and these ant species sometimes occur at the same sites, but no interaction is observed.

Figures

FIGURE 8. M. biseratensis, male. A, body, dorsal view; B, chelicera and carapace, lateral view; C, chelicera and fang, ventral view; D, maxillae, labium, sternum and coxae; E, palp, ventral view; F, palp, lateral view; G, palpal tibia, dorsal view. (Scales. A – D: 1 mm; E – F: 0. 25 mm)

FIGURE 10. M. borneensis, male. A, chelicera and carapace, dorsal view; B, abdomen, dorsal view; C, chelicera and carapace, lateral view; D, maxillae, labium, sternum and coxae; E, chelicera and fang, ventral view; F, cymbium, embolus and tegulum; G, palpal tibia, ventral view. (Scales. A – E: 1 mm; F – G: 0.25 mm)

FIGURE 9. M. biseratensis, female. A, body, dorsal view; B, body, lateral view; C, maxillae, labium, sternum and coxae; D and F, internal structure of epigyne, ventral view; E, internal structure of epigyne, dorsal view. (Scales. A – C: 1 mm; D – E: 0.25 mm; F: 0.10 mm)