Myrmarachne lagarosoma Yamasaki, 2018

Yamasaki, Takeshi, Hashimoto, Yoshiaki, Endo, Tomoji, Hyodo, Fujio, Itioka, Takao & Meleng, Paulus, 2018, New species of the ant-mimicking genus Myrmarachne MacLeay, 1839 (Araneae: Salticidae) from Sarawak, Borneo, Zootaxa 4521 (3), pp. 335-356 : 342-346

Myrmarachne lagarosoma Yamasaki sp. nov.

( Figs 23–33 )

Type material. Holotype: male ( FRCS; LMy20120910_4ha), Lambir Hills National Park , Sarawak, Borneo, 10.IX.2012, Katayama leg. Paratype: 1 female ( MNHAH; LMy20090223_E6), same locality as in the holotype, 23.II.2009, T. Endo leg.

Etymology. The specific name, a noun in apposition, is derived from Greek adjective “lagaros” and noun “soma”, meaning a narrow body, referring to the spider general shape.

Diagnosis. Slender species with very long pedicel; in external appearance, carapace, pedicel, and abdomen all approximately equal in length. Male and female of M. lagarosoma sp. nov. are clearly distinguishable from other Asian Myrmarachne species, except M. leptosoma sp. nov. (described below), M. cornuta Badcock, 1918 and M. tintinnabulum sp. nov. (described below), by the very long pedicel. Myrmarachne lagarosoma sp. nov. is distinguishable from M. cornuta and M. tintinnabulum by pedicel with long posterior sclerite (lorum), much longer than anterior lorum, and distinguishable from M. leptosoma by the absence of swollen structure on anterior dorsal plate of pedicel.

Male ( Figs 23–26 ). Carapace slender, strongly constricted between cephalic and thoracic parts. Cheliceral paturon slightly shorter than carapace; prolateral and retrolateral margins of fang furrow not distinctly separated, with eleven teeth on fang furrow. Fang without tooth-like apophysis. Pedicel very long; anterior part (lorum) much longer than posterior part. Abdomen strongly constricted at anterior part, pear-shaped; dorsum mostly covered with scutum.

Male palp ( Figs 27–29 ). Cymbium oval, without distinct apical macrosetae. Tegulum oval, with spermophore along margin. Embolus coils and tegulum occupying nearly half of venter of cymbium. RTA as a long spine, apically curving inward.

Leg macrosetae. Femur I pd 1, rd 0; tibia I pv 5, rv 5; metatarsus I pv 2, rv 2; femur II pd 1, rd 0; tibia II pv 1, rv 2; metatarsus II pv 2, rv 2; femur III pd 1, rd 0; leg IV with no macrosetae.

Coloration and setation ( Figs 23–25 ). Carapace dark brown, covered with long setae; lateral surface of constriction area densely covered with white setae. Chelicera brown, covered with fine setae. Endite and labium brownish cream. Sternum brown. Pedicel dark brown. Abdomen covered with fine setae; dorsum dark brown; venter gray except for dark brown epigastric area and median light brown area running longitudinally from epigastric furrow.

Female ( Figs 30–32 ). Carapace and pedicel almost the same as in male, except for short cheliceral paturon. Abdomen slender, slightly constricted at anterior part; dorsum as in male.

Epigyne ( Fig. 33 ). Each copulatory atrium small, circular, and placed laterally. Sclerotized copulatory duct beginning from outer edge of posterior margin of copulatory atrium, extending along margin of atrium, connected to spermatheca without twists. Spermatheca spherical. Triangular flattened plate-like median pocket present in front of epigastric furrow.

Leg macrosetae. Patella I pv 0, rv 1; tibia I pv 6, rv 6; metatarsus I pv 2, rv 2; tibia II pv 3, rv 3; metatarsus II pv 2, rv 2; legs III and IV with no macrosetae.

Coloration and setation ( Figs 30–32 ). Almost same as in male, except for white surface of weakly constricted cephalic/thoracic junction. The abdomen is slightly tinged with yellow (this might be due to dye from yellow paper preserved with the specimen.) Also with dorsal abdominal scutum, but not covering entire dorsum.

Measurements (Male/female). Total length 7.0/7.8. Carapace length 2.25/2.53, width 1.06/1.09. Length of cheliceral paturon of male 2.03. Width of eye row I 1.07/1.14: II 0.95/1.03; III 1.08/1.18. ALE–PLE 0.80/0.88. ALE–PME 0.40/0.45. Eye size: AME 0.38/0.40; ALE 0.19/0.21; PME 0.06/0.08; PLE 0.20/0.21. Pedicel length 2.00/2.53. Abdomen length 3.15/3.05.

Distribution. Known only from Borneo.

Remarks. Myrmarachne lagarosoma sp. nov. was collected from the canopy area in a primary forest.

The conspecificity of the male and female was established on the basis of the morphology. The male and female specimens share the same structure of the pedicel, which does not have the swollen dorsum like that of M. leptosoma sp. nov.

In our unpublished results of molecular analyses on mitochondrial gene CO1 and nuclear gene 28S rRNA, M. lagarosoma sp. nov. falls in a clade with M. malayana Edmunds & Prószyński, 2003, M. shelfordii Peckham & Peckham, 1907, M. thaii Żabka, 1985 and M. exasperans ( Peckham & Peckham, 1892) (Yamasaki et al. unpublished). Although the appearance is very different among them, they are very similar in structures of the male palp and epigyne. Therefore, the revival of Emertonius Peckham & Peckham, 1892, as proposed in Prószyński & Deeleman-Reinhold (2010), is worthy of reconsideration from both morphological and molecular approaches.

Figures

FIGURES 23–29. Myrmarachne lagarosoma sp. nov., holotype male (LMy20120910_4ha). 23 dorsal view; 24 lateral view; 25 ventral view; 26 left cheliceral paturon and fang, ventral view; 27 left palp, ventral view; 28 retrolateral view; 29 left palpal tibia, dorsal view. Scales: 23–25: 1 mm; 26: 0.5 mm; 27–29: 0.25 mm.

FIGURES 30–33. Myrmarachne lagarosoma sp. nov., paratype female (LMy20090223_E6). 30 dorsal view; 31 ventral view; 32 lateral view; 33 epigyne, cleared, ventral view. Scales: 30–32: 1 mm; 33: 0.1 mm.