Myrmarachne assimilis Banks, 1930

Yamasaki, Takeshi & Ahmad, Abdul Hamid, 2013, Taxonomic study of the genus Myrmarachne of Borneo (Araneae: Salticidae), Zootaxa 3710 (6), pp. 501-556 : 510-512

Myrmarachne assimilis Banks, 1930

( Figs 6 A–H, 7A–F)

Myrmarachne assimilis Banks, 1930: 210 , Figs 7 , 13 .

Non-type material examined. BORNEO: 5 males, 5 females and 3 juveniles, Poring Hot Spring, Kinabalu Park, Sabah, 10–13 III 2008, T. Yamasaki leg. 1 male and 3 females, Lambir Hills National Park, Sarawak, 6 XI 2009, T. Yamasaki leg.; 3 females, Kota Kinabalu Wetland Centre, Sabah, 22 X 2010, T. Yamasaki leg.; 1 male and 5 females, Lambir Hills National Park, Sarawak, 2–3 XI 2010, T. Yamasaki leg.

Diagnosis. Reddish to yellowish species, in external appearance very similar to weaver ants, Oecophylla smaragdina Fabricius ; thoracic part very low; pedicel long; abdomen strongly constricted. In males, chelicera apically swollen and basally narrow; fang weakly curved, without tooth-like apophysis ( Fig. 6 D). In females, copulatory atria oval; spermathecae elongate-oval; anterior part of sclerotised copulatory ducts twisted; lateral pockets present in front of epigastric furrow ( Figs 7 D–F).

Measurements (male/female). Carapace length 2.75–3.65/2.85–3.35, width 1.62–1.98/1.32–1.58. Abdomen length 3.45–4.15/2.08–4.30. Chelicera length 3.35–4.75. Sternum length 1.75–2.28/1.70–1.98. Width of eye row I 1.36–1.58/1.22–1.44; II 1.26–1.46/1.10–1.30; III 1.56–1.86/1.36–1.62. ALE–PLE 1.12–1.40/1.00–1.18; ALE– PME 0.46–0.54/0.44–0.48. Eye size: AME 0.48–0.54/0.44–0.50, ALE 0.19–0.24/0.19–0.20, PME 0.06–0.08/0.05– 0.06, PLE 0.25–0.29/0.21–0.24.

Male ( Figs 6 A–H). Cephalic part almost flat dorsally, much higher than thoracic part. Thoracic part weakly convex dorsally, lower than lower margin of PLE; in dorsal view lateral margin of thoracic part convex above coxa III. Chelicera apically swollen and basally narrow, with five or six prolateral and twelve to 15 retrolateral teeth. Fang weakly curved apically, without tooth-like apophysis. Sternum slender, and overlapped by coxa II. Pedicel very long. Abdomen gourd-shaped, and strongly constricted anteriorly, with two dorsal scuta.

Palp ( Figs 6 F–H). Tegulum round, with strongly curved seminal reservoir in anterior part and thick reservoir in posterior part. Embolus forming two round coils; embolus coils occupying less than half the venter of cymbium. RTA strongly curved; with palp in lateral view, RTA s-curved. Flange of RTA well-developed.

Leg spination. Femur I md 1–2, pd 1; tibia I pv 5–6, rv 5–6; metatarsus I pv 2, rv 2; femur II pd 1; tibia II pv 2– 3, rv 3; metatarsus II pv 2, rv 2; femur III pd 1; tibia III pv 0–1; femur IV pd 0–1, rv 0–1.

Coloration and pilosity. Carapace light brown; lateral and posterior margins of carapace fringed with white hairs. Chelicera light brown; its inner face black. Maxilla, labium and sternum pale brown or pale orange. Coxae pale brown; coxae III and IV darker than coxae I and II. Dorsum of abdomen covered with fine hairs, and provided with cream markings; dorsal scuta translucent brown; integument except for scuta greyish cream.

Female ( Figs 7 A–F). Cephalic part weakly convex dorsally. Thoracic part weakly convex dorsally; in dorsal view lateral margin of thoracic part convex above coxa III. Chelicera with five to seven prolateral and nine to eleven retrolateral teeth. Sternum almost as in males. Abdomen oval or gourd-shaped, and strongly constricted anteriorly, without distinct dorsal scutum.

Epigyne ( Figs 7 D–F). Copulatory atria containing openings oval. Spermathecae elongate-oval; anterior part of sclerotised copulatory ducts twisted, extending downward from spermathecae. Lateral pockets present in front of epigastric furrow.

Leg spination. Patella I rv 0–1; tibia I pv 5, rv 5–6; metatarsus I pv 2, rv 2; tibia II pv 3, rv 3; metatarsus III pv 1–2, rv 2; patella III pv 0–1; tibia III pv 0–2; metatarsus III pv 0–1.

Coloration and pilosity. Carapace much as in males. Chelicera light brown. Maxilla, labium and sternum much as in males. Coxae I, III and IV pale brown; coxa II cream. Abdomen greyish brown, covered with fine hairs, and partly marked with grey and cream.

Distribution. Luzon (Banks 1930), Borneo.

Remarks. The females of M. assimilis are recorded with morphological description for the first time in the present paper although the females have already known to many scientists who study the ant-mimicry. Myrmarachne assimilis may be related to M. plataleoides (O. P.-Cambridge) distributed on the Asian continent. Although sharing the weaver ant-like form and coloration, they can be distinguished by the structure of the male palp.

Biology. The species is arboreal, and considered to be a mimic of weaver ants, Oecophylla smaragdina . M. assimilis often makes nests on leaves of trees occupied by the ants. The species is abundant in gardens, parks etc.

Figures

FIGURE 6. M. assimilis, male. A, chelicera, carapace and pedicel, dorsal view; B, pedicel and abdomen, dorsal view; C, chelicera and carapace, lateral view; D, chelicera and fang, ventral view; E, maxillae, labium, sternum and coxae; F, palp, ventral view; G, palp, lateral view; H, palpal tibia, dorsal view. (Scales. A – E: 1 mm; F – H: 0.25 mm)

FIGURE 7. M. assimilis, female. A, body, dorsal view; B, chelicera and carapace, 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)

FIGURE 13. M. cornuta, male. A, body, dorsal view; B, chelicera, carapace and pedicel, 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 – G: 0.25 mm)