Caerostris sumatrana Strand, 1915

Omelko, Mikhail M. & Marusik, Yuri M., 2023, Ride on female for “ prima nocta ” or close attachment in the araneid spider Caerostris sumatrana Strand, 1915 (Araneae: Araneidae), Zootaxa 5311 (2), pp. 281-288 : 282-287

Caerostris sumatrana Strand, 1915

( Figs 1–28 )

C. sumatrana: Grasshoff, 1984: 758 , figs 5, 40, 48 (m#).

C. sumatrana: Song, Zhu & Chen, 1999: 262 , fig. 154C–E (f#).

C. sumatrana: Jäger, 2007: 37 , figs 10–17 (m#f#).

For the complete list of taxonomic references see WSC (2022).

Material examined. male, subadult female ( FEFU), LAOS, Vientiane Prov., env. of Nam-Lik Eco-Village , 18°36′53.18″N 102°24′31.87″E, on web, coll. M.M. Omelko-senior, 28 June 2017 .

Diagnosis. The male of C. sumatrana can be easily differentiated from all its congeners by the large, flat conductor covering most of the bulb ventrally (vs. small conductor covering bulb partially). The female of C. sumatrana can be distinguished by the large dorsal carapace humps (vs. small), epigynal hooks overhanging copulatory openings (vs. not overhanging) and wide lamellar bristles on femur IV (vs. narrow).

Redescription. Male ( Figs 5–9 ). Total length 4.73. Carapace 2.73 long, 2.70 wide. Carapace reddish brown anteriorly, dark brown posteriorly. Clypeus dark brown. Chelicerae dark brown anteriorly, reddish brown laterally. Labium and endites dark brown. Sternum brown, 1.26 long, 1.34 wide, widest between second and third coxae, dark brown without pattern. Eye diameters and interdistances: AME 0.26, PME 0.16, ALE 0.10, PLE 0.08. AME–AME 0.30, PME – PME 0.67, PME–PLE 1.04, ALE–PLE 0.05, AME–PME 0.18. Clypeus 0.66 high. Lengths of leg segments as in Table 1 .

Palp brown except for cymbium (dark brown). Leg segments light brown without annulation, covered with white setae. Femur distally dark brown. Metatarsus IV strongly flattened dorsoventrally ( Fig. 9 ).

Opisthosoma 2.74 long, 3.78 wide; dorsally flat, without humps, covered with short whitish setae; dorsally dark brown with yellow anterior edge, ventrally grayish.

Palp as in Figs 10–14 . Femur/cymbium length ratio 0.92; patella slightly shorter than tibia; tibia/cymbium length ratio 0.42. Cymbium narrow, curved. Tibia trapezoid with small, triangular dorsal apophysis (Da. Conductor (C) large, covering whole bulbus dorsally with pointed tip (Ct) and granulation at its base (Cb). Embolus (E) long, coiled with wide base (Eb) and crack (Ec) indicating location of breaking during copulation (unique character of C. sumatrana , not known in its congeners Jäger (2007)). Tegulum (T) large membranous. Subtegulum (St) large with long extension (So) prolaterally.

Female (subadult). Total length 12.59. Carapace 7.07 long, 6.92 wide. Carapace dark brown with short white setae and large humps (Ch) dorsally and laterally. Clypeus dark brown. Chelicerae uniformly dark brown, covered with white setae. Labium and endites dark brown. Sternum brown, slightly darker in middle part, 2.80 long, 3.10 wide, widest between second leg, without setae. AME diameter 0.29, PME diameter 0.27, ALE diameter 0/17, PLE diameter 0.16. AME – AME distance 0.58, PME – PME distance 1.23, PME–PLE distance 2.92, ALE–PLE distance 0.10, AME–PME distance 0.35. Clypeus height 1.33. Lengths of leg segments as in Table 1 .

Palp brown with short setae and long white hairs at prolateral. Leg segments dark brown without annulation, covered with white setae. All segments, except for femora, strongly flattened dorsoventrally ( Figs 1, 2, 4 ). Femur IV with wide, semi-transparent lamellar bristles (Lb, Fig. 3 ).

Opisthosoma 9.72 long, 10.98 wide; dorsally yellowish, with a number of humps, covered with short whitish setae; ventrally grayish. Epigynum was well illustrated by Jäger (2007: figs 13–14).

Notes. Despite the fact that Caerostris sumatrana was described a long time ago, its male had not been discovered until recently ( Jäger, 2007). However, Jäger (2007) provided only two black-and-white drawings of the male palp and one of its prosoma in frontal view. Also, the description of the male did not include any measurements and the body coloration was not discussed. It is worth mentioning that no details about sexual biology of this species have been known prior to our study.

Distribution. India, China (Yunnan), Indonesia (Java, Sumatra), Laos, Malaysia ( Fig. 28 ).

Figures

FIGURE 28. Distribution records of Caerostris spp.: C. almae (1), C. bojani (2), C. corticosa (3), C. cowani (4), C. darwini (5), C. ecclesiigera (6), C. extrusa (7), C. hirsuta (8), C. indica (9), C. linnaeus (10), C. mayottensis (11), C. mitralis (12), C. pero (13), C. sexcuspidata (14), C. sumatrana (15), C. tinamaze (16), C. vicina (17), C. wallacei (18).

FIGURES 1–9. Caerostris sumatrana, female (1–4) and male (5–9). 1, 5, Habitus, dorsal. 6, Same, ventral. 2, 7, Same, anterior. 8, Same, lateral. 3, Femur, lateral. 4, 9, Metatarsus IV, lateral and dorsal. Scale bars, 1 mm. Abbreviations: Ch—carapace humps, Ep—emasculated palp, Lb—lamellar bristles.

FIGURES 10–14. Palp of Caerostris sumatrana. 10, Ventral. 11, 14, Retrolateral. 12, Prolateral. 13, Dorsal. Scale bars, 0.2 mm. Abbreviations: С—conductor, Cb—base of conductor, Ct—tip of conductor, Da—dorsal tibial apophysis, E—embolus, Eb— base of embolus, Ec—crack of embolus, So—outgrowth of subtegulum, St—subtegulum, T—tegulum.

FIGURES 15–23. SEM images of the somatic features of male (15–18) and female (19–23) Caerostris sumatrana. 15, Metatarsus IV. 16, Palpal claw. 17, Trichobothria at metatarsus IV. 18, Setae at metatarsus IV. 19, Metatarsus IV. 20, Lamellar bristles at metatarsus IV. 21, Femur IV, ventral. 22, Lamellar bristles. 23, Palpal tarsus. Abbreviations: Lb—lamellar bristles.

FIGURES 24–27. Male and female of Caerostris sumatrana in situ. Abbreviations: Th—attachment threads.