Diamphidaxona

Smith, Ian M. & Cook, David R., 2006, North American species of Diamphidaxona (Acari: Hydrachnida: Hygrobatidae), Zootaxa 1279, pp. 1-44 : 9-10

Diamphidaxona (s. s.) dolichosoma Cook

( Figs. 23–29 )

Diamphidaxona dolichosoma Cook, 1963 , pp. 114­115, figs. 2, 3, 5, 8; female.

Description. Character states of Diamphidaxona (s. s.). Dorsal edge of camerostome rounded anteriorly and not projecting to anterior end of idiosoma ( Figs. 25, 28 ). Pedipalps with tibia bearing one ventral seta and tarsus with ventral spine­like seta smooth ( Fig. 27 ). Dorsal shield with anterior plate of same width as posterior plate and broadly rounded anteriorly ( Fig. 23 ). Ventral shield with suture lines between third and fourth coxal plates with medial loops deeply arched and lateral loops U­shaped and open anteriorly ( Figs. 25, 28 ). Projections covering insertions of fourth pair of legs with anterior extensions long and directed anteriorly parallel to edges of ventral shield ( Figs. 25, 28 ). Genital field of males separated from ventral shield by distinct band of membranous integument ( Fig. 25 ). Measurements: Male (n=1): Length/width anterior dorsal plate 134/193, length/width posterior dorsal plate 248/188, length/width ventral shield 356/223, length/width genital field 47/92. Lengths pedipalp segments: Tr 15, Fe 53, Ge 33, Ti 50, Ta 29. Lengths leg segments: ITr 30, IBFe 45, ITFe 40, IGe 50, ITi 50, ITa 63; IITr 33, IIBFe 43, IITFe 38, IIGe 48, IITi 50, IITa 60; IIITr –, IIIBFe –, IIITFe 40, IIIGe 49, IIITi 58, IIITa 65; IVTr 65, IVBFe 60, IVTFe 60, IVGe 75, IVTi 80, IVTa 75. Female (n=6): Length/width anterior dorsal plate 149–158/188–228, length/width posterior dorsal plate 257–292/193–233, length/width ventral shield 386–421/233–265, width genital field 79–89. Lengths pedipalp segments: Tr 15, Fe 60–63, Ge 36–40, Ti 58–63, Ta 30–33. Lengths leg segments: ITr 35–38, IBFe 48–50, ITFe 48–53, IGe 53–60, ITi 55–60, ITa 63–70; IITr 35–38, IIBFe 45–50, IITFe 44–48, IIGe 50–55, IITi 53–58, IITa 65–68; IIITr 34–38, IIIBFe 40–45, IIITFe 41–45, IIIGe 50–55, IIITi 58–63, IIITa 63–70; IVTr 73–78, IVBFe 65–70, IVTFe 78–83, IVGe 85–90, IVTi 86–95, IVTa 83–85.

Specimens examined. California: Humboldt Co.: Mattole River beside road to Bull Creek on east side of bridge at Honeydew, 8 August 1987, IMS — 3 females (slides, CNC). Mendocino Co.: Rancheria Creek beside Rt. 128, 7.3 km south of Boonville, 4 August 1987, IMS — 1 male (slide, CNC). North Fork of Navarro River at James A. Jones Redwood Grove, Paul M. Dimmick Recreation Area, 17 September 1995, IMS — 1 female (slide, CNC). Montana: Gallatin Co.: Madison River, 1 September 1961, DRC — holotype female (slide, FMNH). Oregon: Curry Co.: Sixes River at Sixes River Recreation area off Sixes River Road, 1 October 2002, IMS — 1 female (slide, CNC).

Distribution. Streams in California, Oregon and Montana.

Remarks. Adults of Diamphidaxona dolichosoma resemble those of the following group of species in that the projections covering the insertions of the fourth pair of legs are long and extend anteriorly parallel to the edges of the ventral shield, but differ in that the ventral spine­like seta on the tarsus of the pedipalp lacks denticles.

Figures

FIGURES 23 – 29. Diamphidaxona (s. s.) dolichosoma Cook, adults. 23, dorsal shield, female; 24, leg I, female; 25, ventral shield and genital field, male; 26, distal segments of leg IV, male; 27, pedipalp, female; 28, ventral shield and genital field, female; 29, gnathosoma, lateral view, female.