Alycidae (Uusitalo, 2010)

Family Alycidae View in CoL G. Canestrini & Fanzago, 1877

The most convenient way to recognise members of the endeostigmatic family Alycidae is the presence of two pairs of prodorsal sensilla (ve and sci) inserted in separate bothridia ( Figs. 48A, 50A, 52B). The two pairs of sensilla of Proterorhagiidae (two species in North America) are also easily seen in separate bothridia but this family also has unusually enlarged, rhagidiid-like chelicerae ( Fig. 46H). In Nanorchestidae , the anterior pair of sensilla ve is tiny, rarely seen, and in intimate contact with the seta sce, forming a mutual sensory organ, the posterior pair of sensilla being sci (Walter 2009: fig. 14.3F, sensilla le, seta ro and sensilla bo of the author).

One important character is also the presence of solenidia on femora I ( Figs. 2B, 8A, 11C, 18C, 24A, 28B, 30A, 41A–C, 46A). No other endeostigmatids (and very few other mites) have this character ( Bolton et al. 2017). Members of Lordalycidae with neotrichous legs have this character but they have the anterior pair of sensilla ve in a communal depression, the posterior pair of sensilla being sci ( Walter et al. 2009: fig. 13.2A, sensilla vi and si of the authors, cf. Kethley 1990a: 670, 751).

Tendency to add setae on the opisthosoma is also quite common in all genera of Alycidae , although holotrichous species exist in four genera.

Alycid mites have ornate cuticular patterns, particularly the Bimichaeliinae . In the Bimichaeliinae , the most obvious, or primary pattern, comprises many ridges, which may be arranged in a striate, reticulate or rosette pattern. Each of these ridges may be glabrous ( Figs. 52I–K), or has many transverse outgrowths, termed lamellae ( Figs. 52A–C, 52E–G, 53A–C, 53E–G, 53I–K, Uusitalo et al. 2020: figs. 134A, B). These lamellae are much larger in Bimichaeliinae than the Alycinae ( Figs. 45A, 50D). Within this primary pattern there is a finer pattern of granulae ( Fig. 52C, G) or tiny lamellae on fragmented ridges ( Fig. 53C, G, K), termed the secondary pattern. Both forms of patterning are diagnostic within the Bimichaeliinae . An exception is the monotypic genus Glabromichaelia with integument covered only with parallel ridges ( Fig. 52K) as in Lordalycidae ( Walter et al. 2009: fig. 13.2A).

The subfamily Bimichaeliinae is recognised by its reticulate/rosetted primary pattern, although this pattern is sometimes not strongly reticulate but is instead clumped ( Fig. 52C vs. 52G) and in one case is formed by glabrous and parallel ridges ( Fig. 52K). Within this subfamily, the genus Bimichaelia has a secondary pattern of granulae ( Fig. 52A), Minimamichaelia have ridges with granulae and tiny to middle-sized lamellae ( Fig. 51C), while Quartusmichaelia and Laminamichaelia have ridges furnished with some middle-sized lamellae among lots of tiny lamellae, but their setal forms differ ( Fig. 51D, E). Cuticular patterning in Glabromichaelia may also have fine ridges seen by phase contrast microscopy between glabrous ridges ( Fig. 51B).

In contrast, the Alycinae has no distinctive secondary patterning—instead, their cuticle comprises a striate pattern of ridges furnished with many small lamellae. Thus, the cuticular patterning in Alycinae is not described as having primary or secondary patterns ( Fig. 50A, D, G, J). However, under a scanning electron microscope, fine secondary patterning can be seen ( Fig. 10 in Uusitalo 2010), but it lacks lamellae and is fragmented.