Asca von Heyden

De Moraes, Gilberto J., Britto, Erika P. J., Mineiro, Jefferson L. De C. & Halliday, Bruce, 2016, Catalogue of the mite families Ascidae Voigts & Oudemans, Blattisociidae Garman and Melicharidae Hirschmann (Acari: Mesostigmata), Zootaxa 4112 (1), pp. 1-299 : 19-20

Asca von Heyden

FEMALE

Gnathosoma. Anterior margin of epistome variable, even within a species; usually with 2–3 projections, distally denticulate or not; often convex or (rarely) triangular or only slightly prominent; smooth or denticulate. Seta h2 usually shorter than h1, h3 and pc setae, all of which of similar lengths; insertion of h2 slightly to distinctly anterior to insertion of h3. Inner palp trochanter seta usually distinctly longer than outer setae (not in A. evansi Genis, Loots & Ryke ), elongate or not. Deutosternum from narrow to wide, with delimiting subparallel (slightly curved in some species) lateral lines and seven rows of usually 2–7 denticles each (12 denticles in some species). Corniculi usually about twice as long as their basal widths (longer in some species, over three times as long in A. evansi ), with pointed tips, subparallel. Palp tarsal apotele two-tined. Cheliceral digits of similar lengths; fixed digit usually with 4–6 teeth (some species with up to 13 teeth) of variable sizes ( A. pristis Karg with many small teeth) in addition to apical tooth; movable digit usually with two teeth (a few species with three teeth) in addition to apical tooth.

Idiosoma. Ovoid. Dorsum: podonotal and opisthonotal shields not fused, both usually ornamented (smooth or with slight ornamentation in few species), without transverse and nearly straight lines or delineated strip along lateral margins. With few exceptions, without supernumerary setae on dorsal shields (a supernumerary seta on podonotal shield of A. cunliffei De Leon and opisthonotal shield of A. perseae De Leon ). Anterior end of podonotal shield not strongly deflexed; podonotal shield usually with 17 pairs of setae (rarely with 16, 18 or 19; always without z1). Opisthonotal shield with 15 pairs of setae, with posterior tubercles bearing two setae (Z4 and S5; A. acornis Lindquist without tubercles), one of which (S5) may be very short and difficult to distinguish (the few literature reports of 14 pairs may be related to the difficulty in distinguishing a minute seta on the posterior lobe). Unsclerotised lateral cuticle usually with 10–12 pairs of setae (r - R and UR; rarely nine pairs; 13 pairs in A. aethiopica Ryke ; some species reportedly with fewer than nine pairs, but in those cases some setae have probably been overlooked), including r3 (on the dorsal shield in some species), which is usually similar to neighbouring setae. Usually dorsal and lateral setae of idiosoma of similar lengths or posterior opisthonotal and posterior lateral setae distinctly longer; all opisthonotal and posterior lateral setae distinctly longer in some species; most dorsal and lateral setae of idiosoma at most as long as distance to subsequent setae; setae acicular or rod-shaped (rarely leafshaped), smooth to plumose. Venter: often with a pair of lightly sclerotised presternal platelets bearing the first pair of sternal setae (st1); if plates indistinct, then first pair of sternal setae inserted either on lightly sclerotised band of sternal shield anterior to first pair of sternal lyrifissures, or sternal shield bearing all three pairs of setae (st1–st3) and three pairs of lyrifissures (iv1–iv3, the latter on posterior shield margin, which varies from convex to concave or undulate); st1–st3 of similar lengths; st2 about equally distant to st1 and st3. Seta st4 inserted on unsclerotised cuticle (shown on platelets in A. pristis ). Genital shield not wide enough to include iv5, but including st5; posteriorly truncate. Usually 1–2 pairs of metapodal plates and 1–3 pairs of platelets between genital and ventrianal shields; occasionally no platelets or with a sclerotised transverse line. Opisthogaster with eight pairs of setae (seven pairs in A. deleoni nom. nov.) in addition to circumanal setae, of which six (rarely five or seven) pairs on ovoid to semicircular ventrianal shield, which is broad and wider than long; para-anal setae inserted between levels of posterior margin and mid-length of anal opening, usually shorter than post-anal seta. Anal opening small, 1/5 to 1/ 7 of shield length, separate from posterior shield margin. Anterior section of endopodal shield fused with sternal shield; section behind sternal shield usually indistinct (in a few specimens, reduced to small triangular or slender structure between coxae III–IV). Exopodal shield usually represented by an apparently discrete continuous remnant next to coxae III and a remnant fused to posterior end of peritrematic shield.

Peritreme. Extending from stigma to region between j1 and j2, narrower than diameter of stigma. Peritrematic shield wide, usually fused with dorsal shield between level of s1–r2; bearing 1–2 setae near region of fusion with dorsal shield in a few species; posteriorly truncate and broadly fused with exopodal shield beside coxa IV (in some specimens, exopodal shield discontinuous at level between coxae III–IV, in others the section anterior to coxa IV is connected to the posterior section by a narrow bridge).

Legs. All legs with pretarsi. Setation of legs I–IV, genu: 12, 11, 8, 9; tibia: 13 (or 12), 10, 8, 10 (or 9). Leg II not distinctly thickened. Legs without macrosetae.

MALE

Cheliceral digits of similar lengths; fixed digit with four teeth in addition to apical tooth; movable digit with 1–2 teeth in addition to apical tooth; spermatodactyl usually slightly longer than movable digit, but in some species up to three times as long as movable digit; usually slightly curved and with distal end blunt; anterior end of dorsal shield strongly deflexed and/or tapered in some species. Dorsal shield with ornamentation similar to female, in some species including 1–2 r setae . Shape of dorsal setae similar to female. Without presternal platelets. Sternogenital shield with 4–5 pairs of setae (st1–st5; the latter on unsclerotised cuticle in some species) and three pairs of lyrifissures (iv1–iv3); posterior margin truncate to slightly convex. Endopodal shield totally fused with sternogenital shield, or anterior section of endopodal shield fused with sternogenital shield and reduced to an elongate and free strip between coxae III–IV. Ventrianal shield slightly wider than in female, usually with eight pairs of opisthogastric setae in addition to circumanal setae (seven pairs in some species; reduced, with only four pairs of setae in A. aphidioides (Linnaeus) and A. bicornis (Canestrini & Fanzago)) ; not fused with other shields. Metapodal plates absent (with a pair of distinct metapodal plates in A. aphidioides and A. bicornis ). Legs without spine-shaped setae.