Gaeolaelaps praesternalis (Willmann)

Joharchi, Omid, Halliday, Bruce, Khaustov, Alexander A. & Ermilov, Sergey G., 2018, Some soil-inhabiting mites from Zanzibar (Acari: Laelapidae), Zootaxa 4514 (1), pp. 23-40 : 24-25

Gaeolaelaps praesternalis (Willmann)

Hypoaspis praesternalis Willmann, 1949: 115 .

Hypoaspis praesternalis .— Evans, 1953: 272; Ryke, 1963: 2; Ma & Yin, 2011: 119; Saito & Takaku, 2011: 88.

Hypoaspis (Hypoaspis) praesternalis .— Van Aswegen & Loots, 1970: 190.

Hypoaspis (Gaeolaelaps) praesternalis .— Evans & Till, 1966: 173.

Specimens examined: Nine females, Tanzania, Zanzibar, forest litter, 06°16' S, 039°25' E, 8 m. a.s.l., 2 February 2018, coll. S.G. Ermilov, A.A. Khaustov (in TUMZ). One female, Poland, Roztoczanski National Park, Jarugi Reserve, beech forest, 27 September 1986, D. Sell coll.; one female, Poland, Roztocze Region, Hrebenne, beech forest, 6 August 1986, Błoszyk & Hałka coll.; one female, Poland, Roztocze Region, Kąty, xerophyllous grasses, 5 August 1986, Błoszyk & Hałka coll. (in ANIC). One male, Germany, Zorbig, Anhalt-Bitterfeld, 1960, det Willmann (in Zoologische Staatssammlungen, München).

Notes. Gaeolaelaps praesternalis was described from meadow soil in Poland ( Willmann, 1949). It has also been reported from Tanzania ( Evans, 1953; Van Aswegen & Loots, 1970), Germany ( Karg, 1962), South Africa ( Ryke, 1963), Great Britain ( Evans & Till, 1966), Japan ( Saito & Takaku, 2011) and China ( Ma & Yin, 2011). Our specimens agree very well with the description given by Evans & Till (1966). The species is recognised by the presence of 39 pairs of simple setae on the dorsal shield, including two pairs of Zx setae; some setae in the opisthonotal region long enough to reach the base of the next posterior setae; peritreme short, extending to the midlevel of coxa II; a pair of granular pre-sternal plates; and tarsus IV with two very elongate setae pd2, pd3 (88–98).

The literature reveals some confusion about the identity of this species. The original description of Hypoaspis praesternalis by Willmann (1949) is brief, and both the description and illustrations lack some important details. The description of Hypoaspis nolli Karg, 1962 is more detailed, but does not include a direct comparison with H. praesternalis . Evans & Till (1966) synonymised these two species, but did not provide any explanation for that decision, and did not give details of the specimens they examined. Costa (1968) examined specimens of both species from Germany provided by Karg, and distinguished them by the length of the peritreme and the ornamentation of the dorsal shield. Karg (1971 and later papers) separated H. nolli from H. praesternalis on the basis of the length of the peritreme, the length of the setae on the dorsal shield, total body size, and the shape of the spermatodactyl of the male. Kavianpour et al. (2013) and Kavianpour & Nemati (2014) also recognised these two species, but reported that H. praesternalis sensu Evans & Till was actually a misidentification of H. nolli .

Ma (2006) considered that Gaeolaelaps postreticulatus ( Xu & Liang, 1996) is a synonym of G. praesternalis , without providing any supporting evidence. Ma & Yin (2011) then reported that G. praesternalis is very abundant in grassland soil in China. However, Xu & Liang (1996) distinguished between G. postreticulatus and G. praesternalis by the length of some dorsal shield setae, the number of dorsal shield setae, the length of the peritreme, and the shape of the spermatodactyl. Some of these interpretations are questionable, because the statements by Xu & Liang are not always consistent with their own illustrations. If their illustration of the male chelicera is accurate, the spermatodactyl is straight, pointed at the tip, and its free section is 50% longer than the movable digit. In the chelicera of G. praesternalis illustrated by Evans & Till (1966), the spermatodactyl is curved upward, has a large distal knob, and its free section is shorter than the movable digit. Saito & Takaku (2011) showed the spermatodactyl of G. praesternalis from Japan as extremely long, curved downward, and with a blunt tip. Ma & Yin (2004) also illustrated a very long spermatodactyl for this species, with a blunt tip that curves upward. We have examined a male of G. praesternalis identified by Willmann (from Zörbig, Germany, 1960, therefore not a type specimen). Its spermatodactyl is sharply bent upward, distally pointed, and its free section is much shorter than the movable digit. Willmann (1949) described the metasternal setae of the female of G. praesternalis as inserted on small triangular plates. Ryke (1963) and Evans & Till (1966) specifically stated that the metasternal plates are absent, and the metasternal setae are inserted in the soft integument. This evidence from both the males and females strongly suggests that different authors have used the name G. praesternalis to refer to several different species.

We have been unable to locate the holotype of H. praesternalis . It is not present in the Willmann collection in the Zoologische Staatssammlungen, München (Stefan Friedrich, pers. comm.). Our identification of specimens from Zanzibar is supported by comparison with three females from Poland in ANIC (identified by Halliday).