Bimichaelia pallida ( Ewing, 1913 )

Bimichaelia pallida ( Ewing, 1913) View in CoL

( Figs. 6E–G, 23A–G, 24A–F)

Michaelia pallida Ewing, 1913: 125 , fig. 2; holotype from Oregon, Corvallis .

Bimichaelia pallida View in CoL .— Thor & Willmann 1941: 144; McDaniel 1980: 177; Uusitalo 2010: 65.

Description. Dorsum (n= 2 males, Figs. 6E, G, 23A, C, D). Length 600 and 720 µm; reticular primary pattern formed by rosette groups of 5–6 roundish loops around each seta; dorsal setae numerous (ca. 300), acicular, with a few tiny and thin barbs basally; under phase-contrast microscopy, only 2 longer barbs clearly distinguished on both sides of main cilium, other barbs forming a basal thickening of base (cf. Fig. 52B, C); on prodorsum, clearly reticulate pattern of large lamellae from sensillar area to finely striated naso, setae larger and more ciliated than opisthonotal setae, anterior pair of sensilla ve simple, sparsely barbed basally.

Venter ( Fig. 23E–G). Genital valves each with 14–18 genital setae; 7 pairs of eugenital setae (male); 6 anal setae per valve.

Gnathosoma ( Figs. 23B, C, 24F). Chelicerae straight; subcapitular and palpal setae with several long cilia; baculiform palpal solenidion supported by one eupathidion, the other eupathidion being free; joint between palpal genua and femora complete.

Legs ( Figs. 23D, 24A–E). Solenidial formula for tarsi, tibiae, genua and femora on legs I, II, III and IV, respectively: 3B-2B-0-0, 1B-1B-1B-1B, 2C-1\2C-1C-1C, 2C-1B-0-0.

Type material. Fifteen high-quality photos of two cotypes ( Figs. 6E–G, adult and deutonymph) of Michaelia pallida n. sp. from moss, Corvallis, Benton Co., Oregon, USA, 3 March 1912, H.E. Ewing. Deposited at the Smithsonian National Insect & Mite collection, collection number USNMENT01779862_ Michaelia_pallida . 2 males as Bimichaelia pallida (Ewing) from moss, 1.7 mi E. Crown Point, Corbett, Multnomah Co., Oregon, USA, 20 April 1964, G.B. Wiggins & R.S. Scott. Deposited at the Acarology Laboratory, Ohio State University, collection number AL0586. Male on slide NA19 was used for drawings in the redescription.

Differential diagnosis. The species can be segregated from other members of the genus by 2 ceratiform solenidia on genu I (all other species have 1, 3 or 4 ceratiform solenidia); and the combination of character states: large size; independent segments of palpi; barbed basis but otherwise simple sensilla ve; and 2–3 of the basal barbs together with the long main acicular cilium clearly visible. B. logani has sensilla ve barbed from top to bottom, and 5–6 clearly visible cilia on dorsal setae.

Remarks. The original figure of Michaelia pallida presented by Ewing (1913: fig. 2) shows the generic character states of Bimichaelia ( Fig. 23D; listed in the genus diagnosis). The original description was based on 3 specimens also collected in Corvallis, Oregon. Ewing reported the similar size and alveolate integument in the text. According to McDaniel (1980), the records in Banks (1915) and in Thor & Willmann (1941) obviously concern the same specimens.

The redescription of Bimichaelia pallida is based on two male specimens, collected ca. 100 km northeast from the type locality, and recorded as Bimichaelia pallida on the labels on two slides at OSU. Only one third of the dorsal setae are present in the original depiction by Ewing (1913), when compared with the OSU specimens (ca. 100 µm, Fig. 23D vs. 300, Fig. 23C) and specific characters like solenidial numbers are overlooked. However, reexamination of the two cotypes revealed hundreds of disconnected and scattered setae around both cotypes in the medium ( Figs. 6E–G, Dr. Ronald Ochoa, in litt.). B. pallida was coded as ‘ pal ’ in Uusitalo (2010).

The depository of the third specimen of the type series of Michaelia pallida , mentioned by Ewing (1913), is unknown. According to Kethley (1979), the H. E. Ewing Historical collection is split between Illinois Natural History Survey, Natural Resources Building, Urbana, Illinois 61801, and the Museum of Comparative Zoology, Harvard University. Neither collection currently holds the material of B. pallida (Dr. Kathleen Reid Zeiders, in litt. and Dr. Ardis Baker Johnston, in litt., respectively).