Leucauge behemoth new species

Figs 1 E−6

Plesiometa sp.: Avilés et al., 2001: 625, fig. 4.

Leucauge sp.: Salomon et al., 2010: 446, fig. 1C.

Holotype: Female from ARIE do Projeto Dinâmica Biológica de Fragmentos Florestais, Manaus, Amazonas, Brazil, 15/VIII/2003, A. Pacheco coll., (IBSP 342780) . Paratypes: male and four females from Reserva Florestal Adolfo Ducke (2°55’22.0”S 59°58’29.0”W), Manaus, Amazonas, Brazil, 20/XI/2013, B. Faleiro coll. (UFMG 18051); four males and six females from Igarapé do Acampamento, ARIE do Projeto Dinâmica Biológica de Fragmentos Florestais, Manaus, Amazonas, Brazil, 15/VIII/2003, A. Pacheco coll. (IBSP 97726); male and two females, same data (IBSP 97728); four males and two females, same data (IBSP 97729) .

Other material examined. BRAZIL, three females from Parque Nacional da Serra do Divisor (8°2′39″S 73°33′55″W), Cruzeiro do Sul / Mâncio Lima, Acre 14/III/1997, L. Resende & R. S. Vieira coll. (IBSP 12638) ; two males and four females, same data (IBSP 12634); female, same data, 18/III/1997 (IBSP 12211); female and two immature from Rodovia Transamazonica, Km 530, Amazonas 26/ VI /1979, E. Froelich coll. (IBSP 5855) ; female and immature, same data, II/1987 (IBSP 5865); three females from Parque Nacional do Jaú (2°15’0”S 62°38’0”W), Novo Airão, Amazonas 18/ VI /2012, R. A.K. Ribeiro coll. (UFMT) ; male and two females from Benjamin Constant (4°22′58″S 70°1′51″W), Amazonas, VII/1985, A. Pontual coll. (IBSP 97724) ; male and four females, same locality, VII/1984, A. Cerrutti coll. (MNRJ 13047); male, female and two immature from Fazenda Esteio, Reserva do km 41 (02°22’34”S 59°52’39”W), Manaus, Amazonas, 29/VIII/1994, E. Venticinque coll. (IBSP 6238) ; seven females and immature, same data, (IBSP 6237); two females and four immature, same data (IBSP 6235); male, two females and immature, same data (IBSP 6234); four females, same locality, VIII/1994, E. Venticinque coll. (IBSP 6094); male and female from ARIE do Projeto Dinâmica Biológica de Fragmentos Florestais, Km 41, Igarapé do Acampamento (02°22’34”S 59°52’39”W), Manaus, Amazonas, 15/VIII/2003, A. Pacheco (IBSP 97725) ; two males and six females, same data (IBSP 97727); male and female from Reserva Florestal Adolfo Ducke (2°54’2.14”S 60°5’12.24”W), Manaus, Amazonas, VII/1999, M.O. Gonzaga & G.F. Dutra coll. (IBSP 26695) ; male and two females, same locality, 21/ VI /1995, Delgado coll. (IBSP 7382); male and two females from Barra dos Bugres (15°4′22″S 57°10′51″W), Mato Grosso, XI/1984, A. Cerrutti coll. (IBSP 315621); three males, nine females and six immatures, same data (MNRJ 13048) . COLOMBIA, Male and three females from Puerto Asis Road, (0°40’36”N 76°52’38”W), Orito, Provincia Putamayo, 24-25/VIII/1973, V. Leist coll. (SMNK) . ECUADOR, two males and five females from Estacíon Biológica Jatun-Sancha (1°03’57.5”S 77°37’00.2”W), Napo, 5/XII/2009, A.J. Santos coll. (UFMG 9125) . PERU, two males and one female from Centro de Investigaciones Jenaro Herrera (4°53’44.8”S 73°38’50.1”W), Provincia de Requena, Distrito Jenaro Herrera, Región Loreto, 4/IV/2013, C.A. Rheims and R. P. Indicatti coll. (IBSP 233558) ; female, same data (IBSP 233629); male and two females, same data (DZUB 11010); three females, same data (IBSP 237055) .

Etymology. The specific name is a noun in apposition taken from the mythological beast behemoth. The epithet was chosen to reference the remarkable size of this species.

Diagnosis. The males of Leucauge behemoth n. sp. resemble Leucauge argyra by the presence of a dorsal hook on the cymbium of the palp (Figs 1 C−G, 4C−E,5A), but can be distinguished by the longer paracymbium and by lacking the dorsobasal process(Figs 1E, 1G, 4 C−D; Levi, 1980: fig 69). The females of L. behemoth n. sp. also share with L. argyra the lateral ridge and the ventral process on the epigynum (Figs 1B, 2 C−F). They differ by the shape of the ventral process, rounded instead of conical in L. behemoth n. sp. (Figs 2 C−F, 4A−B). This species differs from most Leucauge species by the lack of an anterior hood on the epigynum of females, by its large size compared to other Neotropical congenerics (8.8 to 11.9 mm) and posterior half of abdomen black in dorsal view (Figs 2 A−B, 3).

Description. Female. Paratype from ARIE do Projeto Dinâmica Biológica de Fragmentos Florestais, Manaus, Amazonas, Brazil (IBSP 97726). Total length 10.76. Carapace 4.60 long, 0.60 high, glabrous, light orange. Cephalic region 1.98 wide, slightly darker. Thoracic region 3.68 wide. Clypeus 0.26. Eyes with small black rings. Eyes measurements: AME 0.21, ALE 0.19, PME 0.17, PLE 0.19; Eyes interdistances: AME-AME 0.16, AME-ALE 0.29, AME-PME 0.22, ALE-PLE touching, PME-PME 0.25, PME-PLE 0.33. Chelicerae 2.14 long, 0.98 wide, brownish orange with dark edges. Fangs 0.97 long, dark brown. Endites 1.26 long, 0.62 wide, brown with proximal edges orange. Labium 0.64 long, 0.76 wide, brown. Sternum 1.68 long, 1.72 wide, brownish orange with sparse setae. Coxae and trochanter light orange with few setae, other articles blackish brown with dense setae and very sparse macrosetae. All femurs bear feathered trichobothria, but they are more conspicuous on leg IV. Leg formula: 1243. Leg measurements: Leg I. femur 10.32 / patella 2.26 / tibia 8.58 / metatarsus 10.36 / tarsus 2.23 / total 33.75; II. 8.46 / 2.04 / 7.06 / 9.10 / 1.96 / total 28.62; III 4.76 / 1.16/ 2.98 / 4.39 / 1.40 / total 14.69; IV 8.36 / 1.60 / 5.61 / 7.49 / 1.66 / total 24.72. Palp measurements: femur 1.43 / patella 0.63 / tibia 0.92 / tarsus 1.57. Abdomen 7.00 long, 3.99 wide, 4.23 high. Dorsum covered with silver guanine patches on the anterior half, heart line and its branches without patches, posterior half black with two median parallel lines of guanine dots. Lateral colors as in dorsum, black half without guanine patches laterally. Venter black from the epigastric furrow to the spinnerets, with a pair of lateral parallel silver lines. Booklungs area yellowish beige. Spinnerets reddish brown. Epigynum 1.62 long, 1.55 wide, dark orange with broad rounded ventral process, covered with setae anteriorly. Atrium and posterior region of ventral process glabrous (Figs 2 C−D, 2F, 4A−B). Copulatory ducts short and wide, oval spermathecae with thin and translucid walls, almost inconspicuous (Fig 2E).

Male. Paratype from ARIE do Projeto Dinâmica Biológica de Fragmentos Florestais, Manaus, Amazonas, Brazil (IBSP 97726). All colors as in females. Total length 9.10. Carapace 4.49 long, 0.82 high, cephalic region 1.89 wide, thoracic region 3.39 wide. Clypeus 0.26. Eyes measurements: AME 0.20, ALE 0.19, PME 0.19, PLE 0.19; Eyes interdistances: AME-AME 0.20, AME-ALE 0.30, AME-PME 0.23, ALE-PLE touching, PME-PME 0.19, PME-PLE 0.34. Chelicerae long 2.06, wide 0.99, covered with small setae. Fangs 0.92 long. Endites 1.18 long, 0.61 wide, labium 0.51 long, 0.63 wide. Sternum 1.52 long, 1.67 wide. Leg formula: 1243. Leg measurements: Leg I femur 12.46 / patella 2.33 / tibia 11.71 / metatarsus 15.17 / tarsus 2.50 / total 44.17; II 10.25 / 2.16 / 8.91 / 11.55 / 2.00 / total 34.87; III 5.49 / 1.22 / 3.35 / 4.73 / 1.21 / total 16.00; IV 9.03 / 1.56 / 6.96 / 9.66 / 1.58 / total 28.79. Palp measurements: femur 3.21 / patella 0.55 / tibia 1.34 / cymbium 1.58. Palp with paracymbium curved, shorter than the tibia; conical cymbial hook with an apical spine; conductor with broad base and tapered apex, covered with small projections; tubular embolus widened in the base, sheathed by the conductor (Figs 1 E−G, 4C−F, 5) Abdomen 5.82 long, 2.62 wide, 2.29 high.

Notes. The main description and measurements were taken from paratypes to prevent causing any damage to the holotype. The holotype and the paratypes chosen for the description came from the same population and were collected together.

This species was studied before its formal description was carried out (see synonymy list). Although the voucher specimens from Avilés et al. (2001) and Salomon et al. (2010) were not examined, they were recognized as conspecifics based on their size, color and colonial structure, high similarity to L. argyra and same locality (Estación Biológica Jatun-Sancha).

Variation. Female total length, 8.8 to 11.8 (n=10), male 8.2 to 11.1 (n=10). Females and males are very similar in size and in color. Females have slightly larger bodies, but shorter legs. The chelicerae are covered by more setae in males, and their legs have larger macrosetae than in females.

Living specimens. Males and females have a brownish orange cephalic region and a green thoracic region. Chelicerae brownish red, darker distally. Endites, labium and sternum blackish brown, lighter on their edges. Legs mostly black, trochanter and coxae green as the thoracic region. Abdomen white on the anterior dorsal half, posterior half black. Lateral edge between these halves with either a large and bright yellow stripe, a thin greenish yellow border, or even absent. Venter black. Booklung covers bright red (Fig 2 A−B, 3).

Distribution. Brazil, Colombia, Ecuador and Peru (Fig 6).

Natural history. We observed 26 colonies in the ARIE (Área de Relevante Interesse Ecológico) Dinâmica Biológica de Fragmentos Florestais, north of Manaus, Brazil. The number of individuals of L. behemoth n. sp. per colony ranged from 3 to 22 adult and young spiders (2 to 27 in Solomon et al., 2010, median size of 19; 25 in Áviles et al., 2001). The colonies seemed to be more common in stretches of the “igarapé” with turbulent waters, which possibly has relation to the increase of number of flying insects or the high emergency of adult insects that have aquatic larval form. This phenomenon was observed in other tetragnathid species that coexist in similar areas with high prey abundance. These species, Tetragnatha praedonia, L. Koch, 1878; T. keyserling Simon, 1980, and T. pinicola L. Koch, 1870 primarily tolerate themselves through variations in the vertical placement of their webs (Yoshida, 1980).

Vertical stratification is also present in colonies of L. behemoth n. sp., and it has been speculated (Salomon et al., 2010) that this colonial organization leads to spiders in different heights having access to different prey communities. We observed between VII/1984 - VII/1985 that spiders smaller than 2 mm do not spin individual orb webs, living on the supporting threads of orbicular webs of colony in aggregations of up to five individuals close to the vegetation. Spiders around 2 mm spin small webs (6−10 cm) positioned a little further away from the vegetation towards the center of the watercourse. Individuals around 4−6 mm spin webs generally close to the surface of the water, whereas larger individuals (body size about 9−11 mm) occupy the intermediate and higher parts of the colonies. Specimens studied in Napo (Ecuador) by Salomon et al. (2010) behaved the same way. When disturbed, the spiders fled in groups to the leaves of the surrounding vegetation. Generally, the escape behavior varies according to the size of the colony. In small colonies all spiders fled to the same leaf, but in larger colonies, groups of two to five spiders fled to the underside of different leaves, returning after 10−20 minutes. Another observed behavior indicates tolerance between conspecific of the same colony, since spiders stayed together without aggression in encounters that take place outside the orb webs (Fig 3D).

Even though other congeneric species such as L. argyrobapta can have aggregate behaviors in the reproductive season (Buskirk, 1986), this is the first species where a complex coloniality with generation overlap has been documented. Its only close relative with similar behaviors is Metabus ocellatus (Keyserling, 1864) (Burskirk, 1975), a Leucauginae from riparian habitats in Central America.