Eidmannella pallida ( Emerton, 1875 )

Nardi, Davide, Pantini, Paolo, Rizzo, Pierluigi, Trespidi, Giacomo, Turetta, Alessandra, Barbieri, Giacomo & Ballarin, Francesco, 2023, A comprehensive update on the morphology and distribution of the invasive scaffold-web spider Eidmannella pallida (Araneae, Nesticidae) with a focus on new records from Italy, Zootaxa 5351 (2), pp. 221-264 : 231-234

Eidmannella pallida ( Emerton, 1875)

Nesticus pallidus Emerton, 1875: 279 , pl. 1, f. 22–27 (♁ ♀).

Microneta gigantea Banks, 1892: 48 , pl. 2, f. 52 (♀).

Nesticus cavicola Banks, 1898a: 186 (♁ ♀).

See the World Spider Catalog for the complete list of references.

Material examined. ITALY: Veneto Region: 41♁, 13♀, Padova, Baone ( DNPC) ; 4♁, 2♀, same locality ( FBPC) ; 2♁, 3♀, same locality ( MSNBG) ; 22♁, 4♀, Cinto Euganeo ( DNPC) ; 3♁, 4♀, same locality ( MSNBG) ; 10♁, 1♀ Rovolon ( DNPC) ; 2♁, same locality ( MSNBG) ; 1♀ Teolo ( DNPC) ; 18♁, 3♀, Torreglia ( DNPC) ; 10♁, 2♀, Vo’ ( DNPC) ; 10♁, 1♀, same locality ( MSNBG) ; 1♁, 1♀ Vicenza, Gambellara ( DNPC) ; 1♁, same locality ( MSNBG) ; 1; 5♁, 1♀ Montebello Vicentino ( DNPC) ; 1♁, same locality ( MSNBG) , all in vineyard with pitfall traps, G. Trespidi & A. Turetta leg.; 1♁, 1♀ Val Liona , D. Nardi leg. ( MSNBG) ; 19♁, 5♀, Venezia, Chioggia , wetland/field margin/crop field, pitfall traps, G. Barbieri leg. ( MSNBG) ; Friuli-Venezia Giulia Region: 1♁, Udine, Muzzana del Turgnano , crop field, pitfall traps, F. Lami leg. ( MSNBG) ; Calabria Region: 2♁, Cosenza , Rende ( MSNBG) ; 5♁, Rossano ( MSNBG) , all in olive orchard, pitfall traps, P. Rizzo leg. Collecting dates and additional information on the examined Italian specimens are provided in Supplementary Materials, Table S2 .

Diagnosis. Eidmannella pallida can be easily distinguished from most Nesticidae by the small size and the pale coloration lacking any dorsal pattern ( Fig. 2E, F ). Males can be further recognized by the following combinations of characters: paracymbium with only 2 short distal apophyses (Di-I, II) and a short ventral apophysis (Va), a trapezoidal radical apophysis strongly protruding from the radix, a thick threadlike embolus gradually thinning in the last trait, a strongly-developed and prominent median process of conductor (Cm) wrapped around the tip of embolus, and a strongly reduced and barely visible retrolateral process (Cr) (vs. different shape and level of development of processes in other nesticids) ( Figs. 2A–D , 3A–E ). Females can be distinguished by the following combination of diagnostic characters of epigynum and vulva: a short and wide scapus (Sc) partially covered by a triangular median plate (Mp), anterior diverticula clearly visible by transparency in the frontal part of epigynum, and large ventral pockets partially covering the copulatory ducts and spermathecae (vs. different shape of epigynum and vulva in other Nesticidae ) ( Fig. 2G, H ). For the separation of E. pallida from other congeneric Eidmannella species see Gertsch (1984: 55).

Redescription (based on specimens from North Italy).

Male. Habitus as in Fig. 2E . Total length. 2.57, Prosoma 1.22 long, 1.01 wide. Carapace rounded, uniformly yellowish with inconspicuous striae. Cervical groove slightly visible, with a light dark margin, fovea indistinct. Eight eyes all well developed, AME the smallest. Eyes measurements: AME = 0.06, ALE = 0.08, PME = 0.09, PLE = 0.09, AME–ALE = 0.05, ALE–PLE = 0.06. Chelicerae, labium, maxillae and sternum of same yellowish color as carapace. Legs uniformly yellowish. Leg formula. I, IV, II, III. Legs measurements: I 5.74 (1.54, 0.48, 1.50, 1.49, 0.74), II 4.35 (1.24, 0.40, 1.07, 0.99, 0.65), III 3.51 (1.04, 0.35, 0.72, 0.85, 0.55), IV 5.03 (1.45, 0.43, 1.22, 1.28, 0.65). Opisthosoma lacking any clear pattern, uniformly greyish with sparce slightly lighter marks on the dorsal and lateral side.

Male palp as in Figs. 2A–D , 3A–E . Cymbium ovoid with 2–3 thicker, barbed hairs on the antero-prolateral margin ( Fig. 2C, D ). Paracymbium with 2 short and blunt, distal apophyses (Di-I, II) and 1 longer and sharper ventral apophysis (Va) ( Figs. 2A, B, D ; 3A, E ). Embolus (E) with a clockwise course, thread-like and long, thick for 2/3 of its length, narrowing in the last trait. Origin of embolus positioned at approx. 6:00 o’clock on radix (Rx). Radical apophysis (Ra) trapezoidal, strongly protruding prolaterally from the radix. Conductor with 3 distinct processes. Median process of conductor (Cm) strongly developed and strongly protruding antero-prolaterally, wrapped around tip of embolus and ending with a sharp tip. Prolateral process (Cp) wide and flat, headed counterclockwise around embolus. Retrolateral process (Cr) small and thick, similar to a small bulge. ( Figs. 2 A−C, 3A–D).

Female. Habitus as in Fig. 2F . Total length 2.97, Prosoma 1.28 long, 1.11 wide. Carapace piriform. Eyes measurements: AME = 0.06, ALE = 0.09, PME = 0.09, PLE = 0.09, AME–ALE = 0.04, ALE–PLE = 0.06. Legs measurements: I 5.84 (1.69, 0.51, 1.46, 1.45, 0.73), II 4.47 (1.33, 0.46, 1.02, 1.06, 0.60), III 3.45 (1.03, 0.43, 0.68, 0.82, 0.49), IV 5.12 (1.58, 0.41, 1.26, 1.25, 0.62). Coloration and other details as in male.

Epigynum and vulva as in Fig. 2G, H . Scapus (Sc) short and wide, elongated laterally, ending with a flat posterior margin. Median plate (Mp) flat, partially covering scapus, ending with a triangular posterior margin ( Fig. 2G ). Copulatory opening (Co) at the lateral sides of scapus. Internal ducts visible through the transparent tegument of median plate. Ventral pockets (Vp) wide, balloon-like, with a wrinkled surface. Anterior diverticula of ventral pockets (Ad), short, comma-like, converging to each other at the center. Copulatory ducts (Cd) S-shaped, headed first internally then anteriorly, gradually converging at the center. Spermathecae (S) round, separated from each other by approximately their diameter ( Fig. 2H ).

Remarks on variation. Male (based on 4 specimens): total length: 2.25–2.57, prosoma length: 1.09–1.22, prosoma width: 0.99–1.01. Female (based on 4 specimens): total length: 2.96–2.98, prosoma length: 1.25–1.28; prosoma width: female: 1.09–1.11.

Eidmannella pallida exhibits a wide range of different phenotypes among different populations with high variability in the coloration and pigmentation of the opisthosoma and the degree of eye atrophy ( Gertsch 1984). Moreover, minor differences in the morphology of genitalia also exist as can be observed in published scientific drawings of this species, sometimes even among the same author ( Dumitrescu 1973). It is currently unclear if such differences can be considered as intraspecific variation of a single morphologically plastic species, or if these phenotypes represent a complex of closely related but distinct species.

Figures

FIGURE 2. Eidmannella pallida, male and female from northeast Italy.A–D Male palp in ventral view (A), in retrolateral view (B), in prolateral view (C), in dorsal view (D). E, Habitus of male. F, Habitus of female. G, Epigynum, ventral view. H, Vulva, dorsal view. Abbreviations: Ad = anterior diverticulum of the ventral pockets; Cd = copulatory duct; Co = copulatory opening; Mp = median plate; S = spermatheca; Sc = scapus; Vp = ventral pocket. Scale bars: A–D, 0.2 mm; E–F, 1 mm; G–H, 0.1 mm.

FIGURE 3. Eidmannella pallida, details of the male palp at the SEM microscope.A, Male palp, general ventral view. B, Detail of radix. C, Tip of embolus. D, Details of embolus. E, Details of paracymbium. Abbreviations: C = cymbium; Ct = conductor; Cm = median process of conductor; Cp = prolateral process of conductor; Cr = retrolateral process of conductor; Di (I, II) = distal apophyses of paracymbium; E = embolus; Et = tip of embolus; P = paracymbium; Ra = radical apophysis; Rx = radix; St = subtegulum; T = tegulum; Va = ventral apophysis of paracymbium. Scale bars: A, 100 µm; B, D, E, 50 µm; C, 20 µm.