Leucauge venusta ( Walckenaer, 1841 )

Dimitrov, Dimitar & Hormiga, Gustavo, 2010, Mr. Darwin’s mysterious spider: on the type species of the genus Leucauge White, 1841 (Tetragnathidae, Araneae), Zootaxa 2396, pp. 19-36 : 24-33

Leucauge venusta ( Walckenaer, 1841)

Figures 1–12

Epeira venusta Walckenaer, 1841: 90 (see comments below about types).

Linyphia (Leucauge) argyrobapta White, 1841: 473 . Type lost ( Levi, 1980:23), Male neotype designated herein, deposited in MNRJ col. number MNRJ 9038 (see comments below about types), from Rio de Janeiro, Brazil. NEW SYNONYMY.

Epeira hortorum Hentz, 1847: 477 .

Tetragnatha 5-lineata Keyserling, 1864: 145.

Argyroepeira hortorum Emerton, 1884: 332 ; Keyserling, 1893: 333; Emerton, 1902: 192.

Argyroepeira venusta McCook, 1894: 242 .

Leucauge argyrobapta Cambridge, 1902b: 16, 1903: 438 ; Petrunkevitch, 1911: 355.

Leucauge venusta ( Walckenaer, 1841) F. O. P.- Cambridge, 1903: 441; Petrunkevitch, 1930: 266; Saito, 1933: 48; Kaston, 1948: 265; Archer, 1951: 6; Wiehle, 1967: 193; Levi, 1980: 25; Coddington, 1990: 17; Hormiga, Eberhard & Coddington, 1995: 324; Dondale et al., 2003: 51; Álvarez-Padilla, 2007: 291; Álvarez-Padilla & Hormiga, 2008: 540; Kuntner, Coddington & Hormiga, 2008: 177.

Leucauge hortorum Banks, 1909: 163 ; Franganillo, 1936: 85.

Leucauge mabelae Archer, 1951: 6 .

Notes on types: Cambridge (1903: 438), in pointing out that it was not possible to settle the identity of Leucauge argyrobapta “with absolute certainty” suggested that “there is a strong probability” that argyrobapta is a synonym of Leucauge formosa (Blackwall, 1863) , the latter also collected in Rio de Janeiro. He also noted that the specimens of Leucauge formosa that he examined (which were part of the Keyserling collection) were “specifically distinct” from Argyroepeira hortorum (= L. venusta ). Despite the noted uncertainty, Cambridge did explicitly equate argyrobapta with formosa (op. cit., p. 538). Fortunately, such synonymy was not followed by subsequent authors. Illustrations of the epigynum and male palp of Leucauge formosa done by H.W. Levi (and available on line at http://www.oeb.harvard.edu/faculty/levi/ leucauge .html) clearly show that this latter species is different from argyrobapta (Levi’s excellent illustrations are based on specimens from Rio de Janeiro, housed in the Keyserling Collection at the Natural History Museum in London, which according to Levi were probably borrowed from John Blackwall). Under these circumstances, the only way to settle the question of the taxonomic identity of Linyphia argyrobapta is to designate a neotype collected in the type locality (Rio de Janeiro), in fulfillment of the qualifying conditions for neotype designation stated in the ICZN (Art. 75.3). As it turns, Linyphia argyrobapta is a junior synonym of Epeira venusta . The type of Epeira venusta is an illustration by John Abbot from his unpublished manuscript on the spiders of Georgia ( USA). Abbot’s original illustration is in the library of the Natural History Museum in London. Walckenaer (1841) used Abbot’s manuscript (p. 13, fig. 113) to describe Epeira venusta . A photocopy of Abbot’s illustration, in the Museum of Comparative Zoology, was examined by Levi (1980) for his redescription of Leucauge venusta . That the name venusta was published in 1841, and before Whites’s argyrobapta , is clear from White’s (1841: 473) footnote about Walckenaer’s work: “ July 2. Since this paper was written the 2nd volume of Walckenaer’s work has been published.“ It is in this second volume where the description of Epeira venusta was first published. Levi and Levi (1961: 54) also provide additional compelling evidence that Walckenaer’s description was published in 1841, and not in 1842 as stated in Bonnet (1945: 625).

Neotypes: Neotype by present designation, male from Brazil, Rio de Janeiro, Botanical garden of the Museu Nacional do Rio de Janeiro, lat. -22.90842, long. -43.223547 21 VIII 2007, leg. Abel Pérez-González, Adriano B. Kury, Thiago S. Moreira, Dimitar Dimitrov and Gustavo Hormiga (deposited in MNRJ).

Diagnosis: Many Leucauge species are very similar and identification can be difficult. Males of L. venusta can be distinguished from similar species [e.g., L. formosa (Blackwall, 1863) ] by the orientation of the conductor, which is more parallel to the tegulum ( Fig. 2 B–C) than in other similar species. The shape of the apical processes of the conductor is also characteristic ( Fig. 2 A–F). Other male genitalic characters which are useful to distinguish L. venusta from similar congeners are: the size and position of the subtegulum with relation to the tegulum and the shape and size of the paracymbium. The epigynum ( Fig. 3 B) is quite similar to that of L. formosa , however, size and shape of spermathecae in L. venusta is unique to this latter species ( Fig. 3 A). Coloration and color pattern in both males and females of Leucauge are important and diagnostic. They often vary considerably among species with similar genitalic morphology, hence, facilitating the correct identification. In live specimens, the abdomen of L. venusta has four distinct red-orange markings (silvery when in alcohol) ( Fig. 1 A–G). Two are ventral and two are dorso-lateral. The ventral markings are parallel and placed laterally on distal third of the abdomen. They join proximally to form a U shaped pattern. The dorsal markings start around the middle of the abdomen and extend parallel to each other.

Description: Male (neotype of Linyphia argyrobapta , from Rio de Janeiro) Habitus as in Figure 4 A–D. When live, carapace ( Fig. 5 D–F) yellowish with green markings along edges and center dorsally. Fovea well marked ( Fig. 5 F). Leg coxae with yellowish bases, rest of legs bright green. Abdomen ( Figs. 4 B–D; 5G; 6A) elongated, proximally with shiny silvery guanine bands and three thinner black lines dorsally – one in center, two more lateral. Two lateral dorsal lines change to red-orange coloration close to middle of abdomen and widen distally. Lateral sides of abdomen with thick shiny silver line close to its dorsal side followed by black line and another silvery line with some yellowish tones followed by bright green. Ventral side of abdomen proximally green with yellowish central mark proximally and thin yellow lateral lines. Distally with a central black area and two lateral red-orange markings forming a U-shaped pattern. Two shiny rounded spots placed just lateral to spinnerets – light yellow when alive, silvery white in alcohol. All colored lines meet on distal tip of the abdomen which is black. Total length 5.50. Cephalothorax 2.35 long, 1.95 wide, 1.16 high. Abdomen 3.15 long, 1.54 wide, 1.47 high. Clypeus height 0.7 times an AME diameter. Sternum ( Fig. 5 D) dark brown; 1.05 long, 0.98 wide. Eyes almost the same size. Lateral eyes juxtaposed on short elevations ( Fig. 5 A, F). Distance between PME 1.5 times their diameter. AME-ALE distance about three AME diameters. Distance between AME almost twice their diameter. PLE-PME distance three times one PME diameter. Chelicerae ( Figs. 4 A; 5A–C) yellowish, darker brown distally. Distal edge of paturon with three anterior and four posterior teeth. Femur I 1.2 times the length of cephalothorax. Pedipalp as in Figures 2 A–F; 6C–G; 7A–D. Palpal tibia length 0.78; cymbium length 0.58. Epiandrous fusules as in Figure 6 B. Femur of leg IV dorsally with two parallel rows of branched trichobothria extending over more than two thirds of its length. Palp as in Figures 2 A–E; 6C–G; 7A–D. Conductor and embolus connect to tegulum with common membrane ( Fig. 2 E, F).

Female (same locality and date as male neotype). Habitus and coloration as in male ( Fig. 1 A–G), slightly larger than male (female total length ca. 1.3 times that of male). Total length 7.45. Cephalothorax ( Fig. 8 A–C) 2.88 long, 2.06 wide, 1.32 high. Abdomen ( Fig. 9 A–B) 4.57 long, 2.40 wide, 2.19 high. Clypeus height 0.5 times an AME diameter. Sternum ( Fig. 9 B) dark brown; 1.39 long, 1.16 wide. Eyes sizes and distribution as in male ( Fig. 9 A, E). Chelicerae as in male ( Fig. 9 C–F). Tracheal system haplotracheate ( Fig. 10 F–G), with median tracheal trunks shorter than lateral, neither of them entering the prosoma. Tracheal atrium with numerous accessory glands ( Fig. 11 A). Tracheal spiracle immediately anterior to spinnerets. Spinnerets as in Figure 10 A–D. Femur IV dorsally with two rows of branched trichobothria as in male ( Fig. 10 E). Epigynum as in Figures 2 A–B; 9C–F; 11B–G. Spermathecae ( Figs. 3 A; 11B, B) membranous and elongated. Fertilization ducts also membranous with numerous accessory glands ( Fig. 11 C, E, F).

Variation: Male cephalothorax length varies between 2.24 and 2.35 (n = 4). Females cephalothorax length varies between 2.30 and 3.00 (n = 117). Total body length in males varies between 5.11 and 5.50 (n = 4) and in females between 5.88 and 9.66 (n = 117).

Distribution: Leucauge venusta is very widely distributed in the New World. Although, common in temperate areas of USA ( Levi, 1980) this species has been already found in the neotropics ( Panama, Colombia, see Cambridge, 1903) and its presence in Brazil extends further south its known distribution range. Leucauge venusta distribution spans from southern Canada to southern Brazil.

Natural history: The natural history of L. venusta is relatively well known. Leucauge venusta spins its horizontal orb web ( Fig. 12 A–F) in vegetation in humid tropical and temperate areas. Emerton (1902), Comstock (1913), Kaston (1947), Levi (1980) and Hénaut et al. (2006) describe their webs. In more temperate areas it is commonly found in irrigated orchards, gardens or vegetation along river banks. The spider usually rests in the center of the web but when disturbed it hides in an off-web retreat. Leucauge venusta webs may vary considerably and in some cases they have a mesh above the orb plane. The variability in web architecture in this species was first noted by Darwin (as quoted in White, 1841: 474): “... but sometimes above, the concentric web, there is an irregular or thin tissue of network ”. The web and foraging biology of L. venusta was also studied in detail by Hénaut et al. (2001). The courtship behavior is described in detail by Castro (1995). Eberhard and Huber (1998) give further details and discuss the differences in the courtship among several Leucauge species.

Figures

FIGURE 1. Leucauge venusta live female from Rio de Janeiro (Brazil): lateral A – D, F; ventral E; dorsal G.

FIGURE 2. Leucauge venusta male (from Rio de Janeiro), palp: prolateral A; retrolateral B; ventral C; sperm duct path D; artificially expanded palp prolateral E; expanded palp retrolateral F. Scale bars: A – C 0.5 mm, D 0.2 mm.

FIGURE 3. Leucauge venusta epigynum (from Rio de Janeiro): dorsal A; ventral B. Scale bars 0.2 mm.

FIGURE 4. Leucauge venusta male from Rio de Janeiro (in alcohol): frontal A; dorsal B; ventral C; lateral D.

FIGURE 5. Leucauge venusta male (from Rio de Janeiro). Chelicerae: frontal A; lateral B; ventral C. Cephalothorax: ventral D; lateral E; dorsal F. Abdomen leteral G. Scale bars: 100 µm.

FIGURE 6. Leucauge venusta male (from Rio de Janeiro). Abdomen ventral A. Epiandrous fusules B. Palp: dorsal C; prolateral D; apical F; apical details E, G. Scale bars: 100 µm A, C, D; 10 µm B, G, E; 20 µm F.

FIGURE 7. Leucauge venusta male (from Rio de Janeiro). Palp details: conductor and embolus A – C; paracymbium D. Scale bars: 10 µm A, C; 20 µm B, D.

FIGURE 8. Leucauge venusta female (from Rio de Janeiro). Cephalothorax: dorsal (cleared) A; ventral B; lateral C. Chelicerae: ventral D; frontal E; lateral F. Leg IV femur G. Scale bars: 100 µm.

FIGURE 9. Leucauge venusta female (from Rio de Janeiro). Abdomen: ventral A; lateral B. Epigynum: dorsal C; caudal D; dorso-caudal E; lateral F. Scale bars: 200 µm A – B; 20 µm C – E; 10 µm F.

FIGURE 10. Leucauge venusta female (from Rio de Janeiro). Spinnerets: ventral A; PLS B; ALS C; PMS D. Leg IV trichobothria E. Tracheae: tracheal system F; tracheal base anteriorly G. Scale bars: 100 µm A, G; 10 µm B, C, D; 2 µm E; 200 µm F.

FIGURE 11. Leucauge venusta female (from Rio de Janeiro). Tracheal atrium caudal view A. Epigynum: dorsal B; anterior view C; lateral D. Spermathecae E. Fertilization ducts F. Spermathecae base G. Scale bars: 10 µm A, E – G; 100 µm B; 30 µm C; 20 µm D.

FIGURE 12. Leucauge venusta (from Rio de Janeiro) female web architecture A – F.