Gaeolaelaps Evans & Till

Beaulieu, Frédéric, 2009, Review of the mite genus Gaeolaelaps Evans & Till (Acari: Laelapidae), and description of a new species from North America, G. gillespiei n. sp., Zootaxa 2158, pp. 33-49 : 35-38

Genus Gaeolaelaps Evans & Till

Geolaelaps Berlese, 1923: 254 , nomen nudum (see Halliday & Lindquist 2007) Gaeolaelaps Trägårdh, 1952: 66 , nomen nudum.

Gaeolaelaps Evans & Till, 1966: 159 , correct original spelling as clarified by Halliday & Lindquist (2007).

Type species: Laelaps aculeifer Canestrini (1884) , by original designation ( Evans & Till 1966).

Diagnosis. Hypoaspidine Laelapidae with the following combination of characters: dorsal shield usually bearing 39 pairs of simple, short to moderately elongate setae; adult female sternal shield longer than broad (rarely broader than long), presternal area weakly sclerotized; epigynal shield tongue-shaped or flask-shaped, not markedly broadened posteriorly, and not touching the inversely subtriangular anal shield; peritrematal and exopodal plates narrow, not expanded posteriorly to coxae IV, and free from each other; without dorsal or ventral hypertrichy, except for 0–3 additional unpaired median setae on dorsal shield; anterior margin of tectum denticulate; deutosternum with six (rarely five or seven) rows of denticles, with at least five denticles each (rarely three or four); chelicerae chelate-dentate, well-developed; leg setation normal for Laelapidae .

Description. Dorsal idiosoma. Holodorsal shield covering part or all of dorsum, suboval or tapering posteriorly from setae r3–4; length 1.4–2.3 × width of shield (see Note 1 below); shield not extending ventrally, usually bearing 39 pairs of simple (2), short to moderately elongate setae (less than 0.2 × the length of dorsal shield), including setae px2–3 between J and Z series, and sometimes with 1–3 additional unpaired Jx setae between J rows; sometimes one or more podonotal setae (e.g. z3) or one or both px setae are missing on the shield, resulting in 38 or 37 pairs of setae on the shield, exceptionally less; rarely other opisthonotal setae missing (3); rarely, setae r2–3 off the dorsal shield, on soft cuticle (4); 1–8 marginal setae (r–R) and 0 to few UR setae on soft cuticle (5).

Ve n t r a l idiosoma. Tritosternum normal, with two pilose laciniae. Presternal area usually weakly sclerotized and lineate, exceptionally with a pair of separate, well-sclerotized platelets (6). Sternal shield of female fused with endopodals beside coxae II–III, with anterolateral corners acutely produced, sometimes extended into narrow (7) arms (endopodal extensions) flanking coxae II anteriorly (8); shield bearing three pairs of fine, simple setae, and two pairs of lyrifissures; seta st1 sometimes off shield in presternal region (9); rarely, third pair of pore-like structures, iv3 (= pst3), captured by sternal shield (10); length 1.1–1.9 × width of sternal shield, or sometimes less in arthropod associates (11); setae st 4 in soft cuticle, near iv3, or rarely st4 on minute metasternal platelets (12) or endopodal platelets (13); posterior margin of sternal shield straight, slightly convex or slightly concave (14). Epigynal shield tongue-shaped or flask-shaped, always rounded and not markedly broadened posteriorly, with broadest width (in posterior portion) 1–1.9 × the width between coxae IV (narrowest point) (15) and 0.6–1.3 × the width of sternal shield (16), and distant from the anal shield by at least the length of the anal opening (17); epigynal shield bearing a single pair of setae (st5); endopodal platelet beside coxae III–IV free, narrow and angular. Peritremes narrow, usually reaching level of coxae I anteriorly, but sometimes shorter, ending near the middle of coxae II (18); peritrematal shield connected anteriorly to dorsal shield, free from exopodal platelets (19), and not extending posteriad coxae IV. Exopodals not expanded posteriad coxae IV. Metapodal platelets small. Anal shield inversely pear-shaped, subtriangular or suboval bearing three circum-anal setae; para-anal setae slightly shorter than or as long as post-anal seta, rarely slightly longer. Soft opisthogastric cuticle with 7–9 pairs of setae (JV s + ZV s) and sometimes a few UR s and/or R s visible ventrally, never hypertrichous (20). Males with holoventral shield usually bearing 10 pairs of setae, sometimes eroded laterally, capturing fewer (3 pairs instead of 5) opisthogastric setae (21), rarely with separate anal shield (22).

Gnathosoma . Tectum with anterior margin rounded or subtriangular, sometimes almost straight, and occasionally with a few short, irregular projections (23), exceptionally with a narrow subtriangular projection (24), always with numerous denticles. Deutosternal groove with six rows of denticles, exceptionally five rows (25) or seven rows (26), usually preceded anteriorly and followed posteriorly by a smooth ridge; deutosternal rows with at least five denticles per row and usually some rows with over 10 denticles; exceptionally basal (6th) row with fewer than five denticles (27), or all rows with fewer than five denticles (28); all rows of denticles of subequal width, or sometimes the posterior rows narrower (29); all rows limited on each side by the lateral margins of deutosternal gutter (30). Corniculi horn-like, relatively short, reaching at most 2/3 of the palpfemur. Palp tarsal claw two-tined, rarely three-tined (31). Both sexes with cheliceral digits chelatedentate, well developed, female movable digit with two teeth, exceptionally with a row of 5–7 small teeth between these (32); female fixed digit with few to many teeth, sometimes with a row of small teeth past the pilus dentilis; male movable digit unidentate; spermatodactyl free distally, usually short, exceeding the tip of the movable digit by less than 0.5 × the length of the digit, sometimes longer, exceeding the digit by as much as 1–1.5 × (33); pilus dentilis short, setiform; arthrodial process a simple corona. Chaetotaxy of the subcapitulum and of the palps normal for Laelapidae (sensu Evans & Till 1965).

Legs. Chaetotaxy normal for Laelapidae (sensu Evans & Till 1965) (34); ventral setae of femora, genua, tibiae II–IV and many setae on tarsi II–IV usually at least thickened, sometimes spine-like or spur-like; setae of legs relatively short, except some setae on femur II (pd1), femur IV (ad1) and mostly on tarsus IV (ad2, pd2–3) can be elongate, sometimes as much as 0.6–0.7 × the length of tarsus IV (35). Pretarsi I–IV with welldeveloped paired claws, may be reduced on tarsi I (36).

Explanatory notes. Structures referred to above vary in the following species: (1) only arthropod associates have length / width ratios of 1.4–1.5: G. barbarae ( Strong 1995) , blattae ( Strong & Halliday 1994) , glabrosimilis ( Hirschmann et al. 1969), ruggi ( Strong & Halliday 1994) , passalus Rosario (1981), paraculeifer Rosario (1981); (2) a few setae (e.g. J4–5, Z5) may be inconspicuously barbed, e.g. in some specimens of G. aculeifer and G. gillespiei n. sp.; (3) e.g. G. disjuncta ( Hunter & Yeh 1969) , G. circularis Hyatt (1964) , and G. ruggi have 32, 33, and 34 pairs of setae on the shield, respectively; (4) e.g. G. schusteri ( Hirschmann 1966) and G. theodori ( Costa 1969) ; (5) about 18–19 R and UR setae on lateral soft cuticle in G. millipedus Rosario (1981) ; (6) e.g. G. disjuncta ; (7) broad arms in G. etiopicus (Berlese) as illustrated by Van Aswegen & Loots (1971), and G. wufengensis ( Liu & Ma 2003) ; (8) anterolateral corners apparently poorly (not acutely) produced in G. blattae , millipedus , negevi ( Costa 1969; or gracilis Meledzhaeva 1963, see Gilyarov & Bregetova 1977), mohrii ( Ishikawa 1982) ; (9) e.g. G. minor ( Costa 1968) , franzi ( Van Aswegen & Loots 1970); (10) e.g. G. schusteri , G. theodori ; (11) length 0.8–0.9 × width of sternal shield in G. barbarae , paraculeifer, passalus, rarosae Rosario (1981), ruggi , 1.0 × in G. blattae , and 0.6 × in G. rosei ( Strong & Halliday 1994) partly because shield is strongly indented posteriorly; (12) e.g. G. angustus ( Karg 1965) , ruggi , similisetae ( Karg 1965) ; (13) e.g. G. minor , G. vanpletzeni ( Van Aswegen & Loots 1970) ; (14) posterior margin moderately indented in G. barbarae , deeply indented in G. rosei , and with a triangular process in G. wufengensis ; (15) exceptionally broadest width 2.0 × width between coxae IV in G. circularis ; (16) exceptionally 1.5 × in G. etiopicus ; (17) epigynal shield separated from anal shield by about half the length of the anal opening in G. tenuisetus Rosario (1981) ; (18) e.g. G. similisetae , G. nolli ( Karg 1962) ; (19) fused to exopodals beside coxae IV in G. magkadikitus Rosario (1981) , and apparently abutting exopodals in G. vanpletzeni ; (20) exceptionally, two unpaired median setae in JV area on soft cuticle in G. angustiscutatus ( Willmann 1951) ; (21) e.g. G. schusteri , theodori , millipedus ; (22) e.g. G. negevi , G. schusteri ; (23) in G. angustiscutatus , G. vertisimilis ( Karg 1994) , and G. praesternaloides ( Ma & Yin 1998) ; (24) in G.

magkadikitus ; G. wufengensis has an acute median projection; (25) in G. corpolongus Rosario (1981) , G. etiopicus , and G. millipedus ; (26) e.g. G. disjuncta , passalus, tarsalis ( Bhattacharyya 1968), vanpletzeni , wufengensis , in some individuals of G. barbarae , and in the male of G. schusteri ; (27) 6th row with four denticles in G. theodori ; (28) 3–4 denticles in G. spiniseta ( Barilo 1991) ; (29) e.g. 6th row narrower in G. theodori and 4th to 6th r ows narrower in G. queenslandicus ( Womersley 1956) ; (30) exceptionally 6th row widened beyond lateral margins in G. angustiscutatus (Willmann) sensu Karg (1965) ; (31) e.g. G. angustus , G. queenslandicus ; (32) in G. angustiscutatus ( Willmann 1951) ; (33) e.g. G. brevipilis ( Hirschmann et al. 1969) , G. disjuncta , G. ellipsoides ( Hirschmann et al. 1969) , G. postreticulatus ( Xu & Liang 1996) ; (34) G. rosei has 2 pl setae on genu IV; (35) e.g. G. gillespiei n. sp., kargi ( Costa 1968), nolli , queenslandicus ; (36) e.g. G. mohrii .

Remarks. By restoring Gaeolaelaps to genus rank from previous usage at the subgeneric rank ( Karg 1979, 2006), I follow Walter & Oliver (1989) and Farrier & Hennessey (1993) who used Gaeolaelaps as a genus. The concept of the genus used here is narrower than that of Evans & Till (1966) and Gilyarov & Bregetova (1977), mostly by limiting Gaeolaelaps to species with a denticulate tectum, which excludes many species such as H. giffordi Evans & Till (1966) , H. lubrica Voigts & Oudemans (1904) , and H. heselhausi Oudemans (1912) , and a relatively narrow epigynal shield bearing a single pair of setae, which excludes H. sardous Berlese (1911) and most other species classified as Alloparasitus by Karg (1979) or Euandrolaelaps by Gilyarov & Bregetova (1977). This concept is broader than that of Walter & Oliver (1989), who characterized the genus by having spur-like or spine-like setae on the distal segments of legs II–IV, and a fixed digit with a row of small teeth flanked by larger teeth. However, it broadly agrees with the definition of Hypoaspis (Gaeolaelaps) used by Karg (1979, 1982) and of Gaeolaelaps used by Krantz & Ainscough (1990).

Most of the approximately 50 species classified by Karg as H. ( Gaeolaelaps ) ( Karg 1982, 1987, 1989a, 1989b, 1994, 2000, 2003, 2006) probably belong to Gaeolaelaps . However, some of these species show disparate or exceptional character states and therefore may not belong to this group, and are, at least provisionally, excluded from Gaeolaelaps here. For instance, H. kassaii Van Aswegen & Loots (1970) and H. pinnae Karg (1987) have many barbed setae on the dorsal and opisthogastric regions. Hypoaspis ciconia Karg (1979) and H. ardoris Karg (1993) have hypertrichous dorsal shields. Hypoaspis exquisita Karg (1989a) has dorsal setae with spatulate tips and a dorsal shield extending ventrally. Hypoaspis pugni Karg (1979) has many podonotal setae inserted on tubercles, no claws on tarsi I, and an epigynal shield almost blunt posteriorly. Hypoaspis loksai Karg (2000) has an enlarged epigynal shield, 1.6 × as wide as the sternal shield, and almost touching the anal shield. Hypoaspis passali Hyatt (1964) has an epigynal shield almost axeshaped, as many as 9–10 unpaired median opisthonotal setae, and about 20 marginal and submarginal setae on the lateral cuticle. Hypoaspis spiculifer Berlese sensu Van Aswegen & Loots (1970) has only two denticles on the otherwise smooth margin of the tectum. Hypoaspis atomarius Berlese as redescribed by Van Aswegen & Loots (1970) has two ventral setae on genu IV instead of one. Hypoaspis guttaforma Karg (1989b) , H. zachvatkini Buyakova & Goncharova (1972) , and H. angustiscutatus sensu Lapina (1976) have at least some dorsal setae inflated near their bases, as seen in some species of Cosmolaelaps ( Evans & Till 1966) .

The following additional species, mostly described as Hypoaspis , are regarded here as Gaeolaelaps species (see also those mentioned in Explanatory notes above): G. aculeiferoides ( Teng 1982) , concinna ( Teng 1982), dailingensis ( Ma & Yin 1998), debilis ( Ma 1996), deinos ( Zeman 1982), ellipsoides ( Hirschmann et al. 1969) , fishtowni ( Ruf & Koehler 1993) , haiyuanensis ( Bai et al. 1994), krantzi ( Arutunian 1993), marksi ( Strandtmann & Crossley 1962) , matinikus Rosario (1981), paraculeifer Rosario (1981), neoaculeifer ( Hirschmann 1966) , oreithyiae Walter & Oliver (1989) , postreticulatus ( Xu & Liang 1996) , singuloides ( Gu & Duan 1993; described as Androlaelaps ), subminor ( Gu & Bai 1991), taitzujungi ( Samšiňák 1964), and G. tengi ( Gu & Bai 1991) . Additional ‘ Hypoaspis’ or ‘ Androlaelaps’ species may belong to Gaeolaelaps but are not listed here, either because I overlooked the reference or because their description in the literature did not provide sufficient information for placement in the genus.

Species of the genus Hypoaspis sensu stricto described by Costa (1971) are distinct from Gaeolaelaps species and can be differentiated from them by their elongate setae on the dorsal shield (particularly j3, z4, s4–5, and Z4 which is 0.2–0.5 × the length of the dorsal shield), and on femur IV (seta ad1), tarsus IV (setae ad2, pd2–3, which are usually 0.6–1.0 × the length of tarsus IV), usually also on femora II and III (pd1 and ad1, respectively), and sometimes on genu IV (ad1). Species of Hypoaspis also have a subtriangular median projection of the tectum, peritremes free from the dorsal shield anteriorly, and setae z4 and s4 tend to be inserted more laterally on the dorsal shield, resulting in exposed areas laterad j4–5 and z5. They also have a maximum of 37 pairs of setae on the dorsal shield, r2–3 being off the shield.

More distant taxa, such as Androlaelaps (Laelapidae) and some Leptolaelapidae may be confused with Gaeolaelaps on the basis of similarities in dorsal chaetotaxy and the shape of the epigynal shield. Androlaelaps species can be distinguished from Gaeolaelaps by their frequently enlarged pilus dentilis, the presence of seta pl2 on genu IV, and the male chelicerae with the fixed digit reduced and edentate, and the movable digit partially or entirely fused with an elongate spermatodactyl ( Till 1963; Krantz & Ainscough 1990). Leptolaelapids have the spermatodactyl directed posteriorly, often more than seven rows of deutosternal denticles, and sometimes also large metapodal plates ( Ayersacarus ), some setae pilose laterally ( Ayersacarus ) or apically ( Hunteracarus ), or a sternal shield that extends strongly anterior to coxa II ( Leptolaelaps ) ( Evans 1957; Hunter 1964; Costa 1975).