Mermessus jona ( Bishop & Crosby 1938 ) Bishop & Crosby, 1938

Patrick, Brian, Dupérré, Nadine & Dondale, Charles D., 2008, Review of the Nearctic genus Scyletria Bishop & Crosby (Araneae, Linyphiidae), with a transfer of S. jona to Mermessus O. Pickard-Cambridge, Zootaxa 1744, pp. 31-40 : 35-39

Mermessus jona ( Bishop & Crosby 1938) new combination

( Figs. 5–12 )

Scyletria jona Bishop & Crosby 1938:90 , pl. 7, figs. 75, 76 (male); Kaston 1976:25 (male, not female); Buckle et al. 2001:141; Draney & Buckle 2005:153, fig. 35.293 (male); Platnick 2007.

Type specimen. Holotype ɗ, TYPE SPECIMEN LOST. UNITED STATES OF AMERICA: New York: Ithaca, [42.4°N, 76.5°W], 17 May 1924, coll. “in stomach of brook trout by H. J. Pack” ( AMNH). Missing from type vial and presumed lost and/or destroyed.

Other material examined. UNITED STATES OF AMERICA: Connecticut: Middlesex, CT [41.52°N, 72.71°W], 7 Feb. 1951, coll. PFB [P. F. Bellinger], det. Kaston 1951, 1 ɗ ( USNM). Illinois: Cook Co., Swallow Cliff Woods, NW of Palos Park, south site [41.68°N, 87.86°W], 30 May–12 June 1996, carrion trap (squid), elev. 215 m, colls. “M. Thayer et al.,” det. M. Draney, 1 ɗ ( FMNH); Cook Co., Swallow Cliff Woods, NW of Palos Park, south site [41.68°N, 87.86°W], 12–26 June 1996, mini-FIT, elev. 215 m, colls. “M. Thayer et al.,” det. M. Draney, 1 ɗ ( FMNH); Cook Co., Swallow Cliff Woods, NW of Palos Park, south site [41.68°N, 87.86°W], 3–17 April 1997, pitfall trap, elev. 215 m, colls. P. Parrillo & J. Pulizzi, det. M. Draney, 1 ɗ ( FMNH); Cook Co., Swallow Cliff Woods, NW of Palos Park, south site [41.68°N, 87.86°W], 17 April–1 May 1997, pitfall trap, elev. 215 m, coll. P. Parrillo, det. M. Draney, 1 ɗ ( FMNH); Cook Co., Swallow Cliff Woods, NW of Palos Park, north site [41.68°N, 87.87°W], 16–30 May 1997, mini-FIT, elev. 215 m, colls. M. Thayer, A. Varsek, & J. Louderman, det. M. Draney, 1 ɗ ( FMNH); Cook Co., Swallow Cliff Woods, NW of Palos Park, north site [41.68°N, 87.87°W], 17 April–1 May 1997, mini-FIT, elev. 215 m, colls. M. Thayer, A. Varsek, & J. Louderman, det. M. Draney, 1 ɗ ( FMNH); Cook Co., Swallow Cliff Woods, NW of Palos Park, north site [41.68°N, 87.87°W], 17 April–1 May 1997, pitfall trap, elev. 215 m, coll. P. Parrillo, det. M. Draney, 1 ɗ ( FMNH); Cook Co., Swallow Cliff Woods, NW of Palos Park, north site [41.68°N, 87.87°W], 1 May 1997, Berlese funnel, log & leaf litter, elev. 215 m, colls. M. Thayer, A. Varsek, & J. Louderman, det. M. Draney, 1 ɗ ( FMNH); Cook Co., Cherry Hill Woods (W of), NW of Palos Park, north site [41.68°N, 87.88°W], 27 June–10 July 1997, pitfall trap, elev. 210 m, coll. P. Parrillo, det. M. Draney, 2 ɗɗ ( FMNH); Cook Co., Swallow Cliff Woods, NW of Palos Park, south site [41.68°N, 87.86°W], 26 May–9 June 1998, pitfall trap, elev. 215 m, colls. “M. Thayer et al.,” det. M. Draney, 1 ɗ ( FMNH); Cook Co., Swallow Cliff Woods, NW of Palos Park, south site [41.68°N, 87.86°W], 31 March–14 April 1999, pitfall trap, elev. 215 m, colls. J. Louderman & A. Antov, det. M. Draney, 2 ɗɗ ( FMNH); Cook Co., Swallow Cliff Woods, NW of Palos Park, south site [41.68°N, 87.86°W], 31 March–14 April 1999, pitfall trap, elev. 215 m, colls. J. Louderman & A. Antov, det. M. Draney, 24 ɗɗ ( FMNH); Cook Co., Cherry Hill Woods (W of), NW of Palos Park, north site [41.68°N, 87.88°W], 14 April 1999, Berlese funnel, log & leaf litter, elev. 210 m, colls. M. Thayer & A. Varsek, det. M. Draney, 1 ɗ ( FMNH). New York: Jamesville, Onondaga Co., 3 miles N of Route 173 [42.98°N, 76.07°W], 9 May 1981, old field, coll. D. Sillman, 4 ɗɗ 3 ΨΨ ( CNC). Ohio: Bath Nature Preserve, north of Akron [41.18°N, 81.65°W], 14–28 May 2003, plot B1 trap 3, from pitfall in grassland, coll. L.B. Patrick, det. C.D. Dondale & L.B. Patrick, 1 ɗ 1 Ψ ( CNC); Bath Nature Preserve, Bath Township, Summit Co. [41.18°N, 81.65°W], 14–28 May 2003, plot B2 trap 4, from pitfall in grassland, coll./det. L.B. Patrick, 1 ɗ (LBP); Bath Nature Preserve, Bath Township, Summit Co. [41.18°N, 81.65°W], 30 June–14 July 2005, plot B1 trap 2, pitfall trap, upland old-field grassland, coll./det. L.B. Patrick, 2 ɗɗ (LBP); Bath Nature Preserve, Bath Township, Summit Co. [41.18°N, 81.65°W], 14–28 May 2003, plot B4 trap 1, pitfall trap, upland oldfield grassland, coll./det. L.B. Patrick, 1 Ψ (LBP); Bath Nature Preserve, Bath Township, Summit Co. [41.18°N, 81.65°W], 13–27 July 2004, pitfall trap, upland old-field grassland, coll./det. L.B. Patrick, 3 ɗɗ ( DMNS); Bath Nature Preserve, Bath Township, Summit Co. [41.18°N, 81.65°W], 14–28 May 2003, pitfall trap, upland old-field grassland, coll./det. L.B. Patrick, 3 ɗɗ ( AMNH). CANADA: Ontario: 18 km E of Gananoque [44.33°N, 76.17°W], 12 May–9 June 1977, pitfall trap in old field, colls. C.D. Dondale & J. Redner, 5 ɗɗ ( CNC); Wainfleet Marsh, 8 km S of Welland [42.92°N, 79.3°W], 14–20 June 1988, coll. A. Stirling, 1 ɗ ( CNC).

Etymology. The type specimen was found in the stomach of a brook trout. The specific epithet is a biblical reference to the tale of Jonah and the whale, making it a proper name in apposition. Thus, the apparent feminine gender of the specific epithet does not change with the masculine genus Mermessus .

Diagnosis. This species is properly transferred to the genus Mermessus based on the generic diagnosis by Miller (2007), wherein males have a prolateral excavation of the radix and a free ventrally recurved tailpiece ( Figs. 5, 8 ), an embolic division that is as tall as it is long, a median tooth of the radix ( Fig. 8 ), the absence of anterior radical process, lack of a series of teeth around the margin of the carapace common to the closely related genus Erigone , and no palpal patellar tooth. Females do not have the terminally divided ventral plate of the epigynum ( Fig. 10 ) typical of most species of Mermessus ( Millidge, 1987; Miller, 2007), but do share an undivided ventral plate with other, atypical epigyna within the genus (e.g., M. entomologicus ( Emerton 1911) , M. index ( Emerton 1914) , and M. indicabilis ( Crosby & Bishop 1928) ; see Miller, 2007 and Millidge, 1987).

Distinguishing this species from other species of Mermessus are the deep groove of the tibial apophysis that potentially gives the appearance of two apophyses ( Fig. 7 ), the large and quadrate paracymbium ( Figs. 5, 6 ), the long copulatory ducts creating a “U” shape and terminating at the spermathecae in a short lateral turn towards the midline of the epigynum ( Fig. 10 ), and the extremely small size.

Description. Male: from the Bath Nature Preserve, Summit Co., Ohio, USA: total length 1.08 mm; carapace 0.48 mm long, 0.33 mm wide; carapace smooth, shiny, lacking pits and lobes, dull yellow with diffuse pattern of very light orange radiating from midline; anterior portion around eye region and clypeus slightly darker than remaining carapace; 3 erect setae along midline; sternum strongly concave and light yellow with sparse setae; endites with sparse setae on ventral surface, and blunt and lightly sclerotized along anterior margin. In lateral view, carapace level in anterior two-thirds, then gently sloping to pedicel in posterior third; carapace margin whitish along posterior half. Anterior eye row procurved, with eyes closely situated together; anterior median eyes small, just less than half the diameter of anterior lateral eyes. Anterior lateral eyes and posterior lateral eyes with reflective tapetum, while anterior median eyes and posterior median eyes apparently lack a tapetum. Posterior eye row slightly procurved; posterior median eyes large, oval, and separated by at least the diameter of anterior median eyes; anterior lateral eyes and posterior lateral eyes nearly touching. Clypeus with small, erect seta just below anterior median eyes. Chelicerae light orange with sparse setae, each with a single lightly sclerotized spur on antero-prolateral face in distal fourth of the chelicera, and with 5–8 stridulatory ridges; cheliceral promargin and retromargin each with five denticles. Abdomen unicolor, nearly white, with short sparse setae; colulus one quarter the length of anterior spinnerets; posterior lateral spinnerets and anterior lateral spinnerets conical, with posterior lateral spinnerets subequal in length to anterior lateral spinnerets. Legs dull yellow, slightly darkening distally; coxa IV with stridulatory pick situated distally on retrolateral side; TmI 0.45; TmIV absent; dorsal tibial macrosetae 2221.

Femur and patella of palpus normal and light yellow with stridulatory pick at base of femur; tibia darker than patella; tibia ( Fig. 7 ), cup-shaped, with dorsal portion rising to a heavily sclerotized apophysis that terminates in two blunt teeth (prolateral view) subequal in length. In mesal view, tibia with a deep groove which runs from the separation between the two blunt teeth of the tibial apophysis to the base of the cymbium. Paracymbium large, quadrate, smooth, with distinct spur on dorsal margin, with blunt hook on ventral margin, and with proximal end bearing five setae ( Figs. 5, 6 ). Embolus lightly sclerotized, with its blackened tip protected by a translucent embolic membrane ( Fig. 8 ). Embolus situated distally on radix ( Fig. 8 ; the “embolic division” in Bishop & Crosby, 1938), radix with mesal tooth (“ventral projection” of Millidge, 1987), and with large hooked tailpiece (“median projection” of Millidge, 1987) ( Fig. 5, 8 ). Lateral to the hooked tailpiece is the heavily sclerotized, spoon-shaped distal suprategular apophysis ( Figs. 5, 6 ), which may easily be confused for a portion of radix.

Female: from 18 km E of Gananoque, Ontario, Canada: total length 1.08 mm; carapace 0.42 mm long, 0.35 mm wide. Description is as for the male with the following deviations: chelicerae lacking spurs; cheliceral

Epigynum ( Fig. 10 ) weakly sclerotized, with copulatory openings situated side-by-side at base of epigynum and barely covered by the undivided ventral plate of epigynum; copulatory ducts well sclerotized and laterally arching away from copulatory openings towards the spermathecae ( Figs. 9, 10 ), terminating at the spermathecae in a short, lateral turn towards midline of the epigynum ( Fig. 10 ). Spermathecae broadly separated and situated anteriad to anterior margin of ventral plate ( Figs. 9, 10 ); fertilization ducts oriented mesally. Epigynal dorsal plate small and weakly developed ( Fig. 11 ).

Variation. Males: Six males gave the following (mean ± 1 SD): total length 1.03 ± 0.10 mm; carapace 0.52 ± 0.06 mm long, 0.39 ± 0.06 mm wide. Carapace dull yellow or whitish to light orange; sternum light yellow to whitish with sparse setae.

Females: Three females gave the following (mean ± 1 SD): total length 1.05 ± 0.09 mm; carapace 0.43 ± 0.05 mm long, 0.33 ± 0.05 mm wide.

Natural history. Little is known of the natural history of this species. Other than the lost holotype specimen and a few specimens from Illinois, specimens of this species have been caught largely in pitfall traps, generally in open habitats such as grasslands, though the Illinois specimens were caught in a degraded oak savannah. Thus, M. jona is likely an epigeal spider of grassland and oak savannah habitats. Nearly all documented specimens are males, leading us to conclude that males are relatively mobile.

Remarks. In Draney & Buckle (2005), this species replaces Scyletria at couplet 179. Mermessus jona keys to " Eperigone " index in Millidge's (1987) key. Kaston (1976) reported also capturing female specimens of M. jona , which we examined and determined not to be female M. jona specimens.

Distribution. Fig. 12 . Until recently, the species was only known from the type locality in New York, as well as Connecticut ( Kaston 1976) and possibly Maryland ( Muma 1944), though Muma's material could not be found for verification. Specimens have since been collected in Ohio and Illinois in the USA, as well as in Ontario in Canada.

Figures

FIGURE 12. Geographic distribution of Scyletria inflata Bishop & Crosby 1938 (filled circles) and Mermessus jona (Bishop & Crosby 1938) new combination (crosses).

FIGURES 5 – 11. Mermessus jona (Bishop & Crosby 1938) new combination. 5. Male palpus, ventral view; 6. Male palpus, retrolateral view; 7. Male palpal tibia, dorsal view; 8. Expanded male palpus, schematic illustration; 9. Spermathecae, ventral view; 10. Epigynum, ventral view; 11. Spermathecae, dorsal view. Scale bars = 0.1 mm.