Hexura rothi Gertsch & Platnick

Cokendolpher, James C., Peck, Robert W. & Niwa, Christine G., 2005, Mygalomorph spiders from southwestern Oregon, USA, with descriptions of four new species, Zootaxa 1058, pp. 1-34 : 11-15

Hexura rothi Gertsch & Platnick

Figs. 1 , 3 , 5 , 9 , 16

Hexura rothi Gertsch & Platnick 1979: 2627 , figs. 64–66, 68–69; Platnick 2005.

Material Examined (m = male, f = female, i = immature). Oregon (all collected in 2001 by Niwa and Peck USFS): Curry County: Galice Ranger District, Siskiyou National Forest, N42°38’46”, W123°55’00” to N42°36’06”, W123°51’23” (1128–1402 m elevation), 25 June (7f, 11i), 9 July (5f, 18i), 23 July (10i), 6 Aug. (2f, 20i), 20 Aug. (2f, 11i), 4 Sept. (6f, 7i), 17 Sept. (6m, 8f, 4i), 9 Oct. (136m, 7f, 14i). Grants Pass Resource Area, Medford District, Bureau of Land Management, N42°38’46”, W123°54’46” to N42°36’02”, W123°53’43” (1036–1280 m elevation), 25 June (3f, 4i), 9 July (3f, 11i), 23 July (1i), 6 Aug. (9i), 20 Aug. (2f, 8i), 4 Sept. (1i), 17 Sept. (1f, 6i), 9 Oct. (29m, 6f, 13i). Josephine County: Galice Ranger District, Siskiyou National Forest, N42°36’18”, W123°47’13” to N42°32’53”, W123°35’59” (640–1234 m elevation), 25 June (8f, 18i), 9 July (2f, 9i), 23 July (4i), 6 Aug. (9i), 20 Aug. (1f, 5i), 4 Sept. (1f, 1i), 17 Sept. (2m), 9 Oct. (28m, 1f, 6i). Grants Pass Resource Area, Medford District, Bureau of Land Management, N42°36’35”, W123°48’03” to N42°32’52”, W123°37’05” (533–1539 m elevation), 25 June (5f, 7i), 9 July (1f, 7i), 23 July (1f, 6i), 6 Aug. (6i), 20 Aug. (7i), 4 Sept. (2i), 17 Sept. (2m), 9 Oct. (44 m, 2f, 2i). Illinois Valley Ranger District, Siskiyou National Forest, N42°16’35”, W123°22’53” to N42°01’34”, W123°27’42” (945–1646 m elevation), 25 June (7f, 11i), 9 July (5f, 3i), 23 July (10i), 6 Aug. (6i), 20 Aug. (2f, 16i), 4 Sept. (1f, 1i), 17 Sept. (11i), 9 Oct. (29m, 4f, 2i). Ashland Resource Area, Medford District, Bureau of Land Management, N42°17’27”, W123°21’36” to N42°00’18”, W123°30’53” (518–1372 m elevation), 25 June (3f, 28i), 9 July (3f, 5i), 23 July (13i), 6 Aug. (1f, 15i), 20 Aug. (1f, 8i), 4 Sept. (1f), 17 Sept. (1f, 5i), 9 Oct. (15m, 3f, 5i).

Diagnosis. The presence of only four spinnerets in H. rothi will separate it from other members of the genus; which have six spinnerets.

Distribution. This species has only been recorded from Curry, Douglas, Jackson, Lane, and Josephine Counties of southwestern Oregon ( Figs. 1 , 3 ).

Wandering Activity. Collection of mature males was restricted to the early fall, with 96% trapped on 9 October 2001 ( Fig. 5 ). Females were active over the entire sampling period and immature activity was highest in late June–early July and September–October.

Comments. Previous habitat information is limited to a single record collected from myrtle duff ( Gertsch & Platnick 1979). Opler and Lattin (2001) speculated that H. rothi may be an old­growth forest obligate. Our data expand this knowledge of this species considerably, and indicate that H. rothi occupies a wide range of mid­ and latesuccessional coniferous habitats. Although restricted to the western Siskiyou Mountains, it was found in all 28 sites surveyed. It was most abundant in cool, high elevation sites [ABCO­ABMAS/QUSA2 and ABCO/SYMO plant association (25.4% and 21.8% of the total, respectively)] and least abundant in warm, lower elevation sites [PSME/Dry Shrub sites (5.8%)].

Hexura rothi appears to be more tolerant of drier conditions than H. picea , which is found in moister areas of northwestern Oregon and western Washington. Opler and Lattin (2001) suggested that H. picea requires the constant availability of moisture associated with old­growth and coastal habitats.

Within the study area, H. rothi appears to be widespread and abundant as it was the most common spider collected (395 individuals, or 14.4% of total spider abundance). Overall, it was 2.6 times more abundant in the Grant Pass area than in the Cave Junction area. Gertsch and Platnick (1979) reported that an egg sac was discovered with a female collected 22 July. The egg sac contained about 80 eggs.

Figures

FIGURE 1. Map of Oregon showing study areas within the Siskiyou and Cascade Mountains and a list of mygalomorph species found in each area [relief map modified from: http: // www. flag. wr. usgs. gov / USGSFlag / Data / maps / Oregon. gif (accessed 31 August 2005)]. Insert shows position of region within the USA.

FIGURE 3. Map of southwestern Oregon (insert shows position of region within state) showing the distribution of Antrodiaetus occultus Coyle (triangles), Antrodiaetus montanus (Chamberlin & Ivie) (diamond), Atypoides gertschi Coyle (squares), and Hexura rothi Gertsch & Platnick (circles). Symbols from this study are closed whereas those recorded by Coyle (1971) and Gertsch & Platnick (1979) are open.

FIGURE 5. Abundance of (male, female and immature) Hexura rothi Gertsch & Platnick collected in pitfall traps from western Siskiyou Mountains during 2001.

FIGURES 8 – 11. Dorsal view of male body. 8, Microhexura idahoana Chamberlin & Ivie (note spur on tibia I); 9, Hexura rothi Gertsch & Platnick; 10, Atypoides gertschi Coyle; 11, Antrodiaetus ashlandensis n. sp. Not to scale; see text for approximate sizes of the different species. Arrows indicate sclerotized patches.

FIGURES 16 – 21. Characters of Mecicobothriidae and Antrodiaetidae. 16, Hexura rothi Gertsch & Platnick (male: 16, ventral view of spinnerets). 17 – 18, Atypoides gertschi Coyle (male: 17, dorsolateral view of chelicerae; 18, ventral view of spinnerets, arrow indicates third spinneret). 19 – 20, Antrodiaetus ashlandensis n. sp. (male: 19, dorsolateral view of chelicerae; 20, ventral view of spinnerets). 21, Antrodiaetus montanus (Chamberlin & Ivie) (male: dorsolateral view of chelicerae, insert shows dorsal view of chelicera with even coat of setae on middle portion). Not to scale.