Glenognatha, SIMON, 1887

Álvarez-Padilla, Fernando & Hormiga, Gustavo, 2011, Morphological and phylogenetic atlas of the orb-weaving spider family Tetragnathidae (Araneae: Araneoidea), Zoological Journal of the Linnean Society 162 (4), pp. 713-879 : 762-764

GLENOGNATHA SIMON, 1887 ( FIGS 36–40 )

Type species: Glenognatha emertoni Simon, 1887 . The holotype of G. emertoni is a male specimen from Arizona ( USA), deposited at the Museum National d’Histoire Naturelle , Paris ( Levi, 1980).

Diagnosis: Glenognatha species can be distinguished from all other tetragnathid genera by the following combination of characters: body under 5 mm in length; abdomen oval to spherical, length less than one and a half times its width ( Levi, 1980; Hormiga & Döbel, 1990: figs 3, 12, 25); posterior tracheal spiracle anteriorly displaced and located in the middle of the abdomen venter ( Fig. 36A ); median tracheal trunks divided into numerous small tracheoles ( Fig. 36C–G ); spermathecae present but lacking epigynum and fertilization ducts ( Fig. 38A, B , see also Dimitrov et al., 2007); and tegulum spherical and considerably larger than the conductor and embolus ( Fig. 39B ).

Description: Female: thoracic fovea absent ( Fig. 37B ). Ocular area higher than the carapace lateral margins ( Fig. 37E ). Sternum as wide as long ( Fig. 37F ). Labium trapezoidal, wider than long, and rebordered. Chelicerae slightly divergent, anterior cuticle smooth as in clypeal area ( Fig. 37C ). Cheliceral boss present. Clypeus higher than two AME diameters ( Fig. 37E ). Eyes subequal in size; lateral eyes slightly smaller. PME without canoe-shaped tapetum, with rhabdoms arranged in loops; PLE with canoe-shaped tapetum ( Levi, 1980: figs 261, 262). Median tracheal trunks considerably wider than lateral tracheae and branching into several tracheoles at the tip and on the sides, some of these tracheoles extend to the prosoma; the lateral tracheae present fewer branches ( Levi, 1980: figs 260, 275). Tracheal spiracle wider than long and with fewer than four accessory glands on each side ( Fig. 36F, G ). ALS with c. 12 piriform spigots ( Hormiga et al., 1995: fig. 25B). PMS with two aciniform spigots between the cylindrical and minor ampullate silk gland spigots but without any aciniform spigots over the anterior surface ( Fig. 36H ; Hormiga et al., 1995: fig. 25C). Femora IV without trichobothria. Epigynum absent, copulatory opening spiracle-shaped with both margins slightly sclerotized. Spermathecae well sclerotized and connected to a membranous sac, probably homologous to an enlargement of the uterus externus ( Figs 38C, D , 40B ). Accessory glands openings located on separate pits, concentrated on the copulatory ducts, and with their bases enlarged ( Fig. 38B, C , see also Dimitrov et al., 2007).

Male: size and somatic morphology similar to the female, but with more divergent chelicerae, without cheliceral boss and bearing distal apophyses ( Fig. 37A, D, G ). PLS triplet is present in the adult. Epiandrous fusules immersed in a transverse depression, arranged linearly. Lower margin of epiandrous plate enlarged ( Fig. 36I ). Palpal patella without macrosetae; palpal tibia as wide as long ( Fig. 39E ). Paracymbium almost as long as cymbium ( Fig. 39E ). Conductor-tegulum attachment well sclerotized, located on the centre of the tegulum ( Fig. 39B ). Embolus tubular, without basal apophyses ( Levi, 1980: figs 280, 289). Sperm duct spiralled, its diameter considerably wider on its middle section ( Fig. 40A ).

Natural history: This genus includes 20 species with a worldwide geographical distribution; most described species inhabit the north temperate regions ( Levi, 1980; Hormiga & Döbel, 1990; Bosmans & Bosselaers, 1994 and references therein). The webs of Glenognatha heleios Hormiga & Döbel, 1990 are horizontal with c. 15 radii, more than 30 spirals and open hubs. Some species have split radii (G. Hormiga, unpubl. data). Their webs are usually found near the ground of marshes, waterlands, or near meadows, but also in forests and agricultural fields ( Levi, 1980; Hormiga & Döbel, 1990: fig. 2). The phenology of some North

764 F. ÁLVAREZ-PADILLA and G. HORMIGA

American Glenognatha species have been studied ( Hormiga & Döbel, 1990). In addition, the mating behaviour and natural history have been studied recently for G. emertoni Simon, 1887 (Danielson- François, 2006). The web building behaviour of an undescribed Glenognatha species was documented by Eberhard (1982).

Taxonomy: Glenognatha has never been revised, with the exception of the North American species ( Levi, 1980; Hormiga & Döbel, 1990), and its monophyly has never been tested. The diagnosis and description for Glenognatha was based on Glenognatha foxi , species coded for the phylogenetic analysis, plus the information for the species included in Levi (1980) and Hormiga & Döbel (1990). All recent phylogenetic analyses have recovered Glenognatha as sister to Pachygnatha with morphology alone and molecules combined ( Hormiga et al., 1995; Álvarez-Padilla, 2007; Dimitrov & Hormiga, 2009).

Figures

Figure 36. Glenognatha foxi abdomen: A, tracheal spiracle. B, cuticle of the abdomen, close up of median lateral section. C, median tracheae. D, median trachea ramifications. E, median tracheae transversal cut. F, tracheal spiracle lateral view. G, tracheal spiracle posterior view. H, posterior median spinnerets. I, epiandrous fusules. All images from SEMFAP029.

Figure 37. Glenognatha foxi cephalothorax: A, male dorsal view. B, female dorsal view. C, female chelicera. D, male chelicera. E, female tangential view. F, female cephalothorax ventral view and sternum. G, female lateral view. All images from SEMFAP029.

Figure 38. Glenognatha foxi female genitalia: A, genital spiracle. B, spermathecae. C, dorsal view. D, lateral view. All images from SEMFAP029.

Figure 39. Glenognatha foxi male pedipalp: A, tarsal organ. B, ventral view. C and D, conductor and embolus lateral view and apical view, respectively. E, ectal view. F, dorsal view. All images from SEMFAP029.

Figure 40. Glenognatha foxi genital anatomy illustrations: A, pedipalp cleared ventral view. B, cleared female genitalia.