Antrodiaetus pacificus Simon
Creators: name: Cokendolpher, James C.
name: Peck, Robert W.
name: Niwa, Christine G.
Publisher: name: Zenodo
Year: 2005
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Araneae
Antrodiaetidae
Antrodiaetus
Antrodiaetus pacificus

description: Antrodiaetus pacificus (Simon)   
Figs. 1, 4, 7, 15, 32, 54  
 Antrodiaetus pacificus: Coyle 1971:347, figs. 121–122, 131, 147–149, 160, 170, 175–177, 197– 203, 244–247, 284–291; Niwa & Peck 2002:791; Platnick 2005 (see for complete synonymy).   
 Material Examined (m = male, f = female). Oregon (all collected by Niwa and Peck USFS): Jackson County, Ashland Watershed, Ashland Ranger District, Rogue River National Forest, 1998: N42°9’50.2”, W122°42’24.9” (926–1024 m elevation), 20 July (7m), 17 Aug. (12m), 1 Sept. (7m, 1f), 29 Sept. (6m), 11 Oct. (3m); N42°8’58.0”, W122°41’14.3” (1219–1268 m elevation), 20 July (2m), 17 Aug. (7m), 1 Sept. (4m); N42°8’58.0”, W122°42’24.9” (1000–1146 m elevation), 8 July (1m), 20 July (4m, 1f), 17 Aug. (15m), 1 Sept. (8m), 29 Sept. (4m), 11 Oct. (4m); N42°8’5.7”, W122°42’24.9” (1463 m elevation), 15 June (1f), 20 July (3m), 17 Aug. (18m), 1 Sept. (3m); N42°8’5.7”, W122°41’14.3” (1317–1365 m elevation), 20 July (1m), 17 Aug. (12m), 1 Sept. (4m).   
Jackson County, Ashland Resource Area, Medford District, Bureau of Land Management, 1999: N42°10’42.4”, W122°22’24.5” (1372–1524 m elevation), 2– 4 Aug. (19m), 16–18 Aug. (2m); N42°5’29.1”, W122°27’6.9” (1372–1524 m elevation), 2– 4 Aug. (15m), 16– 18 Aug. (17m), 13–15 Sept. (1m). N42°5’29.1”, W122°22’24.5” (1372–1524 m elevation), 2– 4 Aug. (2m). Curry County, 2001: Galice Ranger District, Siskiyou National Forest, N42°38’46”, W123°55’00” to N42°36’06”, W123°51’23” (1128–1402 m elevation), 9 July (1m), 23 July (6m), 6 Aug. (5m), 20 Aug. (9m), 4 Sept. (6m), 17 Sept. (1m). 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), 23 July (2m), 6 Aug. (7m), 20 Aug. (3m), 4 Sept. (1m). Josephine County, 2001: Galice Ranger District, Siskiyou National Forest, N42°36’18”, W123°47’13” to N42°32’53”, W123°35’59” (640–1234 m elevation), 23 July (4m), 6 Aug. (4m), 20 Aug. (3m), 4 Sept. (2m). 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), 23 July (2m), 6 Aug. (1m), 20 Aug. (2m), 4 Sept. (2m), 17 Sept. (2m). Illinois River Valley Ranger District, Siskiyou National Forest, N42°16’35”, W123°22’53” to N42°01’34”, W123°27’42” (945–1646 m elevation), 9 July (3m), 23 July (10m), 6 Aug. (4m, 1f), 20 Aug. (3m), 4 Sept. (4m), 17 Sept. (1m). 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 (1m), 9 July (3m), 23 July (10m), 6 Aug. (3m, 1f), 20 Aug. (4m, 1f), 4 Sept. (3m), 17 Sept. (2m), 9 Oct. (2m).  
 Diagnosis. The presence of a cheliceral distodorsal projection and low percentage of ensiform macrosetae in the prolateral brush on tibia I [0–3% (0–27% Blue Mountains population)] will separate this species from all others.   
 Abbreviated Description. With 2–3 separate dorsal abdominal sclerotized patches (Fig. 15); male genital plate with sclerotized parts same thickness throughout, undivided, recurved (Fig. 32); chelicerae with distodorsal projection, without setae on upper ectal surface; with prolateral brush of macrosetae on tibia I, 0–3% [0–27% Blue Mountains population] of macrosetae ensiform; tibiae I with 3–17 macrosetae retrolaterally, without large heavy macrosetae ventrally; tibia and metatarsus I not swollen in lateral view; metatarsus I weakly sinuous or straight, without macrosetae ventrally; tip of palpal outer conductor sclerite closely appressed to inner conductor sclerite; palpal tibia 2.39–2.51 times longer than wide.   
 Distribution. Pacific coast of North America from southern Alaska to central California (Figs. 1, 4; Coyle 1971: map 2).   
 Wandering Activity. During all three years, adult activity was generally highest between late July and early September, although individuals were collected during all months in which trapping occurred (Fig. 7).   
 Comments. Being found in all three study areas, A. pacificus was the most widespread and abundant mygalomorph spider collected. Overall, it was trapped in 57 of 62 sites surveyed. Its relative abundance was similar in each area, ranging from 3.7% of the total spider fauna in the south Cascade Mountains to 4.4% in the western Siskiyou Mountains.   
 Coyle (1971) may have grouped more than one species under A. pacificus. Like Crawford (1988), we believe that the characters presented by Coyle (1971) for specimens from the Blue Mountain (NE Oregon and SE Washington) population are sufficiently different from A. pacificus to justify separation of this taxon into two species; however, this taxonomic work is outside of the realm of the present publication. Our samples match the western coastal population, which represents the true A. pacificus. Coyle’s material may have included examples of one of our new species. In particular, he stated (p. 352): “Occasionally in the western samples and usually in the Blue Mountains samples the three sclerotized patches are continuous.” It is the “occasional western samples” that maybe unrecognized examples of the species we are herein naming A. coylei n. sp. or A. metapacificus n. sp. Our pitfall trap data indicate that A. pacificu s, A. coylei n. sp. and A. metapacificus n. sp. are sympatric in some regions of southwestern Oregon.   
Only six of the 313 adult specimens collected were females. Seminal receptacles (Fig. 54) are like those illustrated by Coyle (1971: figs. 284–291) for this species. The receptacula are evenly sized and the heavily sclerotized stalk of each receptaculum is relatively elongate with a distinctly enlarged terminal region supporting the transparent bulb.  
Variation: The dorsal shield of the prosoma length was measured on all males obtained in 2001 in order to determine the largest and smallest specimens. The results of the measurements are (mean ± s.d.): 6.17 ± 0.33 (n = 119). To examine the possible effects of living in arid scrub brush versus woodlands, dorsal shield of the prosoma lengths were analyzed separately for both regions. The results show no significant difference T­test (t value = ­0.11, P = 0.916) between the two ecotypes (scrub 6.17 ± 0.34; woods 6.18 ± 0.30).
description: Published as part of Cokendolpher, James C., Peck, Robert W. & Niwa, Christine G., 2005, Mygalomorph spiders from southwestern Oregon, USA, with descriptions of four new species, pp. 1-34 in Zootaxa 1058 on pages 30-32, DOI: 10.5281/zenodo.170130