Longicheles Valle, 1953

Emberson, Rowan M., 2010, A reappraisal of some basal lineages of the family Macrochelidae, with the description of a new genus (Acarina: Mesostigmata), Zootaxa 2501, pp. 37-53 : 41-45

Longicheles Valle, 1953

Geholaspis (Longicheles) Valle, 1953: 323 , 343. Type species: Holostaspis mandibularis Berlese, 1904 , by original designation.

Geholaspis (Longicheles) .— Krauss, 1970: 36; Hyatt & Emberson, 1988: 74; Mašán, 2003: 55. Longicheles .— Athias-Henriot, 1968: 241.

Geholaspini with massively developed, elongate, multidentate chelicerae ( Fig. 6 ); epistome with narrow, distally bifid median process ( Fig. 7 ); dorsal setae j5 strongly displaced posteriorly, lying well posterior to setae j6 ( Fig. 8 ); ventri-anal shield with five pairs of pre-anal setae.

The dorsal shield has 28 pairs of setae, which are mainly pilose or plumose distally, except for a variable number of aciculate setae in the j-J series and sometimes one to three setae in the z-Z series. Setae z 1 may be short and pilose, or aciculate to slightly spatulate, and longer than j1. Setae j5 are displaced posteriorly, so that they are mesad and well posterior to j6 ( Fig. 8 ). The ventral setae are mostly simple except toward the posterior lateral margins. The sternal shield has punctate sculpture, without a distinct pattern of lines, and the metasternal plates are free and have the usual seta and pore. The epigynal shield is subtriangular, with a truncate posterior margin and covers strongly developed lateral epigynal sclerites. The ventri-anal shield is usually longer than broad; it has five pairs of pre-anal setae; one or both pairs of the Zv series may be plumose, and the inguinal pores are near the anterior lateral angles. The cheliceral digits are elongate and multidentate, the fixed chela always has more than five teeth, often many more ( Fig. 6 ), and may have a row of accessory teeth on the external face ( L. hortorum (Berlese)) , while the movable chela has at least eight teeth and often have a row of accessory teeth on the external face ( Fig. 6 ). The dentate anterior margin of the epistome is more or less transverse and has a narrow, bifid, median process, which may be distally dissected ( Fig. 7 ). Spermathecal structures are generally not apparent, but the elongate tubuli and rami of two species have been illustrated by Athias-Henriot (1968).

Males unknown.

Protonymphs, where known, have a posterior extension of the hind margin of the podonotal shield into a median lobe bearing setae j5. This extension is probably associated with a posterior migration of the cheliceral retractor muscles.

Notes. Valle (1953) originally distinguished Longicheles from other subgenera of Geholaspis on the basis of two main characters: the elongate nature of the cheliceral digits in Longicheles , and the posterior displacement of setae j5 (setae 18 in his system). The length of the cheliceral digits was expressed as the ratio of dorsal shield length to the length of the movable chela. The posterior displacement of setae j5 was expressed as the ratio of dorsal shield length to the distance between setae z5 and j5 (setae 13 and 18 in his system). Valle’s characters are still considered valid and important in defining the genus. Evans & Browning (1956) introduced an additional character based on the length of setae z1 (M 1 in their system), in which Longicheles was thought to have short setae and Geholaspis s. str. to have long, simple setae. This was shown by Balogh (1958) not to hold for all species of Longicheles . He described L. longisetosus Balogh as having long, simple z1 setae, but with all the other characters of Longicheles . Valle (1963) and Valle & Mazzoleni (1967) subsequently described four additional species of Longicheles , from Mediterranean islands, which all have long, simple z1 setae.

Valle & Mazzoleni (1967) divided the species of Longicheles into four groups based mainly on the dentition and relative length of the cheliceral digits, but also the pilosity of seta j2. However, Mašán (2003) has pointed out that in Central Europe there are two distinct groups of species within Longicheles , based on the length, pilosity, and position of the j1 and z1 setae. These groupings can be extended to all known species of Longicheles and are here referred to as the mandibularis species group, in which setae j1 are close together so that their bases are virtually contiguous and setae z1 are short and distally pilose ( Fig. 8, 9 ), and the longulus species group, in which setae j1 are distinctly separated and setae z1 are longer than setae j1 ( Fig. 10 ). In the longulus species group, setae z1 are usually aciculate or occasionally slightly spatulate/pectinate ( L. bulgaricus Balogh ).

The most distinctive feature of Longicheles is the development of the elongate, multidentate cheliceral digits, which are unique in the family though somewhat similar to those of Lordocheles rykei Krantz. The fixed chela is nearly four times as long (from the tip to the dorsal seta) as they are wide. This development may be associated with the posterior migration of dorsal setae j5 to a position well posterior to j6 ( Valle 1953), and the posterior projection of the hind margin of the podonotal shield in protonymphs of, at least, L. mandibularis (Berlese) and L. hortorum (Berlese) ( Hirschmann 1987, Hyatt & Emberson 1988). This suite of unique apomorphic characters fully justifies the elevation of Longicheles to separate generic status as first suggested by Athias-Henriot (1968), but not generally accepted by subsequent authors.

Although known from North America, Longicheles is mainly European in distribution, having been recorded from Ireland to European Russia ( Bregetova & Koroleva 1960, Hyatt & Emberson 1988), but again seems to be most diverse in Central and Southern Europe ( Valle 1953, 1963, Valle & Mazzoleni 1967, Mašán 2003). Longicheles mandibularis has been introduced to Australia ( Halliday 2001) and New Zealand (new record), evidently by human agency.

Included species: L. longulus species group: L. bianchii ( Valle & Mazzoleni, 1967) , new combination; L. bulgaricus ( Balogh, 1958) ; L. ilvana ( Valle & Mazzoleni, 1967) , new combination; L. lagrecai Valle, 1963 , new combination; L. longisetosus ( Balogh, 1958) , new combination; L. longulus ( Berlese, 1887) , new combination; L. ranzii ( Valle & Mazzoleni, 1967) , new combination. L. mandibularis species group: L. hortorum ( Berlese, 1904) ; L. mandibularis ( Berlese, 1904) , new combination.

Figures

FIGURES 1 – 7. 1 – 3, Dissoloncha superbus (Hull), female. 1. Epistome; 2. Ventri-anal shield; 3. Sacculus complex. 4 – 5. Geholaspis longispinosus (Kramer), female. 4. Chelicera; 5. Epistome. 6. Longicheles hortorum (Berlese) comb. nov., female, chelicera with accessory teeth on external face. 7. Longicheles mandibularis (Berlese), female, epistome.

FIGURES 8 – 11. 8 – 9. Longicheles hortorum (Berlese), female. 8. Dorsum, showing posterior displacement of setae j 5; 9. Anterior dorsal region, showing position and characters of setae j 1, j 2 and z 1. 10. Longicheles longulus (Berlese) comb. nov., female, anterior dorsal region, showing position and characters of setae j 1, j 2 and z 1. 11. Reductholaspis analis (Hyatt & Emberson) comb. nov., female, dorsal shield.