Venter

Venter ( Fig. 42D, E). Ventral setae sparsely ciliated; genital setae 9–10 per genital valve; 10 setae per anal valve.

Gnathosoma ( Figs. 42C, 43J). Subcapitulum slightly neotrichous; chelicerae straight, tiny teeth on movable digits; palpal solenidion supported by two eupathidia.

Legs. ( Figs. 43C, G; in Uusitalo 2010: figs. 133, 134, 136–138). Baculiform solenidia on tibiae I, II and III side by side; solenidial formula for tarsi, tibiae, genua and femora on legs I, II, III and IV, respectively: 3B-2B-0-0, 2B3P-2B1P-2B-1B, 5\6P-1B3P-1P-1P, 2\P-1B-0-0, knob-like famulus I abaxial to solenidion ω2.

Tritonymph (n=1, Figs. 43A, 44B). Dorsum. Length 550 µm; primary pattern and prodorsum are like on adult except the clearly tripartite crista: midline with polygons flanked by narrow strips of lamellae, which disappear before reaching setae vi, anterior sensilla ve with 3 branches distally.

Venter . Genital setae 7 per sclerotized valve, anal setae 4 per valve.

Gnathosoma . Palpal solenidion supported by two eupathidia.

Legs ( Fig. 43B, D–F, H); Baculiform solenidia on tibiae I, II and III side by side; solenidial formula for tarsi, tibiae, genua and femora on legs I, II, III and IV, respectively: 3B-2B-0-0, 2B3P-2B1\2P-2B-1B, 6P-1B3P-1P-2P, 2P-1B-0-0, knob-like famulus I abaxial to solenidion ω2.

Material examined. 1 tritonymph, from litter back dunes, brushy area, AM, Sea pines, Hilton Head Island, Beaufort Co., South Carolina, USA, 15 August 1997, VE LaRoche. Deposited at the Acarology Laboratory, Ohio State University, collection number AL5210, specimen on slide NA34 .

Material from Texas, USA, is deposited at the Texas A&M University, with collection numbers TAMU-ENTO X164-…: 1 female (used for drawings) as Bimichaelia dimixsetosa texana (written in pencil on the label by B. McDaniel) from clumps of grass, roots and soil, 6 miles W Montgomery on highway 105, Walker Co., Texas, 8 January 1983, Eric G. Bolen, slide # X1644846; 1 deutonymph, shin oak ( Quercus havardii ) grassland, 8,2 miles E Floydada where highway US 62 intersects with highway 70, Motley Co., Texas, 14 October 1979, Eric G. Bolen, slide # X1643935; 1 tritonymph as Bimichaelia dimixsetosa , light soils, mesquite grass ( Hilaria belangeri ), Refugio Co., 1 mile S Woodsboro, Refugio Co., Texas, 14 November 1977, Eric G. Bolen, slide # X1645552.

Several high-quality photos of 4 specimens as Bimichaelia arbusculosa from dunes, leaf litter and soil (hojarasca y suelo), low and medium-sized tropical forest (selva baja y media), La Mancha Biological Station (CICOLMA = Centro de Investigaciones Costeras La Mancha), 19°30’N 96°37’W, Veracruz, Mexico, 31 August 1991, 3 September 1991, and 13 June 1992, Ignacio Mauro Vázquez Rojas, slides ALY/VER016, 017, 018, and 021; 1 specimen as Laminamichaelia sp.1 from leaf litter (hojarasca), medium-sized forest and mangrove swamp (selva mediana y manglar), Puerto Morelos Botanical Garden ( JBPM = Jardin Botánico de Puerto Morelos), 20°50’31,2’’N 86°54’10,7’’W, Puerto Morelos, Quintana Roo GoogleMaps , Mexico, 20 November 2014, María Magdalena Vázquez; 1 specimen from leaf litter, low tropical forest floodable (selva baja inundable), JBPM, 20°50’29,9’’N 86°54’10,3’’W, Puerto Morelos, Quintana Roo GoogleMaps , Mexico, 28 January, 2015, María Magdalena Vázquez; 1 specimen (on slide examined by me) as Laminamichaelia sp.1 from leaf litter, medium-sized forest (selva mediana), JBPM, 20°50’27,8’’N 86°54’11,9’’W, Puerto Morelos, Quintana Roo GoogleMaps , Mexico, 28 August 2015, María Magdalena Vázquez. Mexican material is deposited in the LAAH (Laboratorio de Acarología ” Anita Hoffmann ”), Faculty of Sciences at UNAM ( Universidad Nacional Autonóma de México), Mexico City .

Differential diagnosis. Laminamichaelia arbusculosa has character states typical of the genus, such as the stellate pattern of large lamellae; presence of additional plumate setae on both the soft prodorsum and sclerotised in -area; and three baculiform solenidia on tarsi I ( Figs. 40A, 43B). The species is closely related to both L. knowltoni sp. nov. and L. furcula Uusitalo et al. , both of which also have branched sensilla ve ( Figs. 40A, 42A; Uusitalo et al. 2020: fig. 119), but can be segregated by having famulus I close to solenidion ω2 ( Fig. 43B); tibial baculiforms side by side ( Fig. 43B, C, E–H); and there are 3 piliform solenidia on tibiae I ( Fig. 43B, C). L. knowltoni has famulus I in distal position ( Fig. 41B); tibial baculiforms aligned ( Fig. 41A, B, D, E); and piliform solenidia on tibiae I are absent ( Fig. 41B). The African L. furcula also has famulus I in distal position ( Uusitalo et al. 2020: fig. 125); there is a clear gap between the two baculiform solenidia on tibiae I, II and III ( Uusitalo et al. 2020: figs. 125, 126); and 1 piliform solenidion on tibiae I ( Uusitalo et al. 2020: fig. 125), see also Remarks under L. knowltoni .

Differential diagnosis of tritonymph. The American tritonymph is larger than the European adults; strips of crista are not continuous from sensilla ve to naso; solenidia have already been added on tibiae I, tibiae II, and genu I (arrows), which should not appear before adult stages ( Fig. 43C, G; acc. Grandjean 1942: fig. 3A, B), and there are 2 solenidia on genu IV instead of one.

Remarks. The examined female from Texas (500 µm in length) has ca. 540 dorsal setae; 8–10 cells around a dorsal seta; 5–6 branches on sensilla ve; 8 setae on in -area; 10 genital setae per valve; 10 anal setae per valve; and slight differences in the numbers of piliform solenidia. The numbers are at the upper limits when compared to the described specimens from Europe, but the examined material is scanty on both continents. The number of branches of sensilla ve varies, and a specimen with several branches on sensillus ve is known from Europe, too.

The description of the neotrichous tritonymph from USA above is based on a single specimen. The presence of eugenitals may suggest that the specimen is a male ( Kethley 1991, see also Uusitalo 2010: 12). This might also support the idea that the specimens of the American population are larger, because the tritonymph is larger (550µm, Fig. 44B) than the European adults (300–500µm), and males are smaller than females in this family. However, the specimen is flattened, swollen, and intraspecific variation in size is unknown. The numbers of setae and solenidia tend to increase during the development process so that tritonymphs usually have less setae than the adult stages. This fits well with the observed numbers of genital and anal setae (from 7 to 8–10 and from 4 to 4–7, respectively), but the numbers of prodorsal and dorsal setae are similar to European adult stages.

The tritonymph also has piliform solenidia on tibia I, genu I, femur I and tibia II ( Fig. 43B, D, F, respectively, arrows), proposed to appear not until in the adult stage in the European fauna ( Fig. 43C, G, arrows). However, solenidia are also subject to variation due to neotrichy and may even vary between left and right side of the same individual (e.g. solenidia θ and θ₁ on femora I, Fig. 43B, D —small arrows, and 43E­, F—arrows, respectively; and solenidion ω2 on tarsi I in Uusitalo 2010: figs. 108, 109). It is possible that the ontogenetic appearance of solenidia in L. arbusculosa exposed to neotrichy, is not as consistent as implied in the figures 43C and 43G (copied from Grandjean 1942). The random appearance of piliform solenidia of this solitary juvenile support neither conspecificity nor speciation, but baculiform solenidia are arranged in a more or less parallel fashion as on L. arbusculosa .

The length of the flanking strips of crista is the only qualitative difference when comparing the American specimen to the European specimens. However, the amount of intraspecific variation in this feature is unknown in both continents. Thus, the significance in differences of character states between specimens in European and North American populations of L. arbusculosa are not yet fully understood and there is a possibility that the American specimens represent a closely related species (cf. e.g. Canadian beaver vs. European beaver) but based on the scanty material at hand that kind of a conclusion is not possible. The most conservative treatment is to suppose that the examined specimens on both continents are conspecific, and differences are due to intraspecific variation, and perhaps larger American specimens are females, and smaller European ones are males.