Alloseius, Mašán, Peter & Halliday, Bruce, 2009

Mašán, Peter & Halliday, Bruce, 2009, Three new genera of the mite family Eviphididae (Acari: Mesostigmata), Zootaxa 2013, pp. 43-57 : 48-49

Alloseius gen. nov.

( Figs 5−8 , 19, 21 )

Type species Iphidosoma pratensis Karg, 1965 .

Description (female). Dorsal idiosoma. Idiosoma dorso-ventrally flattened. Dorsal shield entire, oval, not completely covering dorsal idiosoma; narrow posterior strip of idiosoma without shield; anterior extension of the shield overlapping onto ventral surface beyond vertex, fused to anterior parts of peritrematal shields to form an arched structure bearing shortened setae j1 and z1. Dorsum with coarse punctate-reticulate sculpture, bearing 28 pairs of setae. Posterior setae J4 and J5 short, columnar in shape, with rounded tips; other setae needle-like. Setae j1 columnar, with rounded tips; z1 fine and pointed, j1 and z1 positioned on ventral extension of dorsal shield, conspicuously shorter than other setae on anterior dorsum.

Ve nt r al idiosoma. Sternal shield well sclerotised, bearing three pairs of setae and two pairs of pores: first pair of sternal pores moderately enlarged. Sternal shield and endopodal platelets II completely fused. Metasternal platelets present, each bearing metasternal seta st4 and associated pore. Genital shield narrow anteriorly, widening posteriorly, with a pair of posterior genital setae. Anal shield subcircular, with irregular undulating margin. Presternal, exopodal and postgenital plates absent. Peritrematal shields well developed, widened. Metapodal platelets present. Ventral cuticle with complicated ornamentation, consisting of striation combined with punctate-reticulate pattern.

Gnathosoma . Palptarsus without paired macroeupathidium. Movable digit of chelicerae bidentate, fixed digit with median hyaline protuberance ( Fig. 19 ). Tectum serrate on margin, with elongated central projection and short lateral prongs.

Legs. Setation of legs I-II-III-IV: coxae 2-2-2-1, trochanters 6-5-5-5, femora 13-11-6-6, genua 11-11-8-7, tibiae 11-10-7-7; tarsi II–IV with 18 setae.

Etymology. The name of the genus is derived from the name of the related genus Alliphis , and from Seius , a proper noun used in the names of many mite taxa.

Notes on the genus. The differential diagnosis of the new genus is based on the combination of the following characters: (1) dorsal shield setae j1 columnar, with rounded tips; (2) anterior dorsal shield expanded ventrally beyond the vertex, so setae j1 and z1 are positioned ventrally; (3) the peritrematal shields are fused with the expanded anterior margin of the dorsal shield to form an arch-shaped antero-ventral shield structure that embraces coxae I; (4) coarse punctate-reticulate sculpture on dorsal shield as well as on striated ventral cuticle; and (5) movable cheliceral digit bidentate, fixed digit with hyaline projection (this projection is not visible in holotype). These character states may be contrasted with those in Alliphis halleri (G. & R. Canestrini, 1881), the type species of the genus Alliphis , as follows: (1) vertical setae j1 lanceolate; (2) anterior dorsal shield not expanded ventrally beyond the vertex, so setae j1 and z1 are positioned dorsally; (3) anterior sections of peritremes not fused with each other; (4) dorsal shield with delicate reticulation, and soft ventral cuticle only with simple striation; and (5) movable cheliceral digit unidentate, fixed digit without hyaline appendage. The hypostomal denticles of Alloseius pratensis ( Fig. 21 ) appear to be longer and fewer than those of Alliphis halleri ( Fig. 22 ), but the significance of this character is difficult to assess without more specimens of A. pratensis . The diagnostic characters that separate Alloseius from Alliphis and from the other new genera described here are summarised in Table 1 .

Character / Genus Alliphis Pseudoalliphis Alloseius Halolaspis gen. nov. gen. nov. gen. nov.

Dorsal sculpture reticulate punctate-reticulate punctate-reticulate rugose-verrucose We have examined the holotype female of Alloseius pratensis , the only known stage of the type species, but it is in poor condition for study. The specimen is strongly flattened, the marginal ventral soft cuticle is assymetrically collapsed, and almost the whole ventral idiosoma is scarcely suitable for examination. Only the anterior marginal region is readily observable. The whole gnathosoma is completely unsuitable for examination, but the dorsal surface and anteromarginal ventral surface are well preserved and clearly visible (see Figs 5 and 6 ). For that reason, the illustration of the ventral idiosoma in Fig. 8 is only a modification of that in Karg (1965). The chelicerae are concealed by surrounding gnathosomal structures and only the tips of cheliceral digits are barely observable, so the hyaline projection on the fixed digit described by Karg (1965) could not be seen. The original description given by Karg (1965) required some amendment (see below), especially in the structure of soft cuticle and the ventral vertex, including its peritrematal shield components. Also, our description and illustration of dorsal shield setae J4 and J5 differ from those of Karg (1965). Karg (1965) shows these setae as pointed and spine-like, but our observation of the holotype showed them to be coulmnar with rounded tips ( Fig. 5 ). Iphidosoma insolentis Ma, 1997 , described from females found under fallen leaves in China ( Ma 1997), is here transferred to Alloseius gen. nov.

Figures

FIGURES 5 – 8. Alloseius pratensis comb. nov., female. 5. Dorsal idiosoma (holotype); 6. Ventral vertex and peritrematal region (holotype); 7. Ventral idiosoma; 8. Tectum. Scale: 100 µm (Figs 5 and 6). Figs 7 and 8 modified from Karg (1965), not to scale.

FIGURES 11 – 24. Morphological structures in Eviphididae, females. 11. Halolaspis hypedon, sternal shield; 12. H. hypedon, sternal shield, different specimen; 13. Pseudoalliphis sculpturatus, chelicera, lateral view of distal segment; 14. P. sculpturatus, chelicera, ventral view; 15. H. hypedon, chelicera; 16. H. hypedon, peritrematal shield; 17. Alliphis halleri, tectum; 18. P. sculpturatus, tectum; 19. Alloseius pratensis, cheliceral digits, lateral view (after Karg, 1965); 20. H. hypedon, tectum; 21. A. pratensis, hypostome (after Karg, 1965); 22. A. halleri, hypostome; 23. P. sculpturatus, hypostome (after Karg, 1963); 24. H. hypedon, hypostome. Scale bars: 50 µm (Figs 11, 12, 15, 16 and 24) and 25 µm (Figs 13, 14, 17, 18 and 20). Figs 19 and 21 – 23 not to scale.