Tennesseellum Petrunkevitch 1925

Dupérré, Nadine, 2013, Taxonomic revision of the spider genera Agyneta and Tennesseellum (Araneae, Linyphiidae) of North America north of Mexico with a study of the embolic division within Micronetinae sensu Saaristo & Tanasevitch 1996, Zootaxa 3674 (1), pp. 1-189 : 172-174

Tennesseellum Petrunkevitch 1925

Tennesseellum Petrunkevitch 1925: 173 . Type species Tennesseellum formicum ( Petrunkevitch 1925) = Bathyphantes formica Emerton 1882 .

Diagnosis: Members of this genus resemble species of Agyneta and Anibontes , but differ from the latter and all other North American Linyphiidae by the position of the spiracle, distant from the spinnerets ( Fig. 33 ).

Description: Male: Total length: 1.5–1.6. Carapace: flat, elongate-oval, strongly granulate ( Fig. 16 ), suffused with dark gray along margin and radiating lines, fovea well marked. Clypeus: height 2–3 ( Fig. 15 ), straight in lateral view. Eyes: rounded, anterior median eye equal or smaller than other eyes ( Fig. 15 ); posterior eye row slightly procurved to straight in dorsal view ( Fig. 16 ). Sternum: smooth slightly longer than wide or as long as wide. Endites: as long as wide, serrula present; occasionally with seta-tipped tubercles. Labium: rebordered, fused to sternum. Chelicerae: longer than wide, excavated ( Fig. 15 ); paturon sometimes with tubercles ( Fig. 584 ); promargin and retromargin with denticles; cheliceral stridulatory organ present ( Fig. 20 ). Abdomen: cylindrical or oval, with or without pattern, sigilla sometimes present ( Fig. 574 ). Colulus: triangular with setae. Legs: uniformly colored; leg formula 4123; prolateral spine on tibia I absent; femur I–III with paired ventral apical spines, single on femur IV; tibia I–IV with two small dorsal spines, Tm I: 0.29–0.31, Tm IV: absent. Respiratory system: demistracheate ( Fig. 33 ); with two wide median trachea, two smaller lateral trachea, wide and fused to the median trachea and one spiracle ( Fig. 33 ). Genitalia: Male palpal femur sometimes with large prongs ( Fig. 570 arrows); tibia with one retrolateral and one dorsal trichobothria ( Figs 570 , 580 ). Cymbium triangular; glabrous depression present with curved ridge ( Figs 570 , 580 ); dorsal and ventral cymbial tubercles absent; prolateral notch absent ( Figs 571 , 581 ). Paracymbium with apical pocket and anterior pocket present, posterior pocket absent ( Figs 570 , 580 ). Embolus sickle-shaped; ventral lamella absent; thumb short, reaching below the embolus proper ( Figs 572 , 582 ). Embolus proper set apically; Fickert’s gland absent ( Figs 572 , 582 ). Anterior terminal apophysis large, striated with numerous, long protrusions; posterior terminal apophysis pointed; lamella characteristica variable ( Figs 573 , 583 ).

Female: Total length: 1.6–2.4. Carapace: slightly elevated, oval, finely granulate; suffused with dark gray along margin and radiating lines; trident mark sometimes present; fovea not well marked. Clypeus: height 1–1.5, straight in lateral view. Eyes: rounded, all equal in size, posterior eye row slightly procurved to straight in dorsal view. Chelicerae: not excavated, promargin and retromargin with teeth; cheliceral stridulatory organ present. Sternum: as long as wide. Abdomen: oval, with or without pattern, sigilla sometimes present ( Fig. 575 ). Spinnerets: (studied for T. formicum only), ALS with one major ampullate spigot and at least five piriform spigots, PMS with one cylindrical, two aciniform and one minor ampullate spigot, PLS with two cylindrical, three to four aciniform spigots, two aggregate and one flagelliform spigot ( Fig. 19 ). Colulus: triangular with three setae ( Fig. 19 ). Legs: uniformly colored; leg formula 4123; prolateral spine on tibia I absent; femur I–III with paired ventral apical spines, single on femur IV; tibia I–IV with two small dorsal spines, Tm I: 0.30–0.35, Tm IV: absent; palp normal or inflated; claw absent. Genitalia: Epigynum consisting of folded scape; proximal part of scape wide; median part of scape variable; lateral lobes short; stretcher small ( Figs 576 , 586 ). The genital pores position is variable, can be situated at the lateral lobes pockets or in the median part of scape ( Figs 579 , 587 ). The copulatory ducts are straight and runs from the genital pores to the receptacula ( Fig. 577 ). The internal genitalia is composed of two receptacula; the fertizilation ducts are short and directed inward ( Figs 578 , 587 ).

Composition: Tennesseellum currently contains two described species: T. formicum ( Emerton 1882) and T. gollum Dupérré 2013 .

Distribution: Nearctic, T. formicum probably introduced in the Marshall Islands.

Natural History: T. formicum has been found in a wide range of natural habitats, in Newfoundland Pickavance & Dondale (2005) found specimens in mixed coniferous woods, Crawford & Edwards (1989) reported the species above tree line on Mount St. Helens and Muma (1980) reported its presence in Pinyon-Juniper and in arid grassland in New Mexico. Furthermore, the presence of T. formicum has been reported in several non-natural habitats. It is also found in agrosystem environments such as, soybean plantations, alfalfa fields, cabbage fields and citrus groves ( Whitcomb et al. 1963, Mansour et al. 1982, Bishop & Reichert 1990, Young & Edwards 1990, Schmaedick & Shelton 2000). Apparently T. formicum is able to survive in natural and non-natural habitats. In fact, Kelton et al. (2011), in their study of phenological dynamics in alfalfa ecosystems, showed that T. formicum life cycles matches the phenology of an alfafa ecosystem and that the spider population can survive agronomic disturbance at the egg stage. This capability to colonise and subsist in different types of habitats enabled T.

formicum to establish itself almost all over North America. This association of T. formicum with agrosystem environments is well established, so much so that it has been qualified as an agrobiont species ( Bolduc et al. 2005).

Bolduc et al. ’s (2005) study of ground dwellling spiders in two vineyards established that T. formicum shows phenotypic variations and has a multivoltine life cycle. T. formicum has also been collected while ballooning in eastern Texas ( Dean & Sterling 1990). In their study, males where evenly distributed from May to September, while females were collected in August and September.

Some Hymenoptera such as Miscophus kansensis , Trypoxylon frigidum frigidum and T. kolazyi have been reported to prey upon T. formicum ( Krombein et al. 1979) . Peterson et al. (2010) showed that T. formicum in laboratory can feed on pollen grains dusted on their webs, another interesting adaptation that could explain its success in colonizing differents habitats.

Figures

FIGURES 31 – 33. Tracheal system, dorsal view. 31. Agyneta decora (O. Pickard-Cambridge 1871). 32. Anibontes mimus Chamberlin 1924. 33. Tennesseellum formicum (Emerton 1882).

FIGURES 9 – 16. 9. Agyneta decora (O. Pickard-Cambridge 1871), palp retrolateral view. 10. A. decora, palp prolateral view. 11. A. decora, female spinnerets anterior view. 12 a. A. decora, female anterior lateral spinneret, anterior view. 12 b. A. decora, female posterior median spinneret, anterior view. 12 c. A. decora, female posterior lateral spinneret, anterior view. 13. Agyneta rurestris (C. L. Koch 1836), palp retrolateral view. 14. A. rurestris, palp prolateral view. 15. Tennesseellum formicum (Emerton 1882), male carapace anterior view. 16. T. formicum, male carapace dorsal view.

FIGURES 580 – 587. Tennesseellum gollum n. sp. 580 – 584, Male. 585 – 587, Female. 580. Palp, retrolateral view. 581. Palp, prolateral view. 582. Embolus, prolateral view. 583. Radical division, retrolateral view. 584. Chelicerae, anterior view (arrow points to large seta-tipped tubercle). 585. Epigynum, dorsal view. 586. Internal genitalia, ventral view. 587. Internal genitalia, dorsal view.

FIGURES 17 – 24. 17. Tennesseellum formicum (Emerton 1882), palp retrolateral view. 18. T. formicum, palp prolateral view. 19. T. formicum, female spinnerets anterior view. 20. T. formicum, male chelicerae lateral view. 21. Agyneta fabra (Keyserling 1886), male carapace anterior view. 22. Agyneta fillmorana (Chamberlin 1919), male carapace anterior view. 23. Agyneta parva (Banks 1896), male chelicerae anterior view. 24. Agyneta minorata (Chamberlin & Ivie 1944), male chelicerae anterior view.

FIGURES 570 – 579. Tennesseellum formicum (Emerton 1882). 570 – 574, Male. 575 – 579, Female. 570. Palp, retrolateral view (arrows points to prongs of the palpal femur). 571. Palp, prolateral view. 572. Embolus, prolateral view. 573. Radical division, retrolateral view. 574. 575. Abdomen, dorsal view. 576. Epigynum, dorsal view. 577. Internal genitalia, ventral view. 578. Internal genitalia, dorsal view. 579. Internal genitalia, lateral view.