A new cheyletid mite Metacheyletia ngaii n. sp. (Acariformes: Cheyletidae) from quills of Corythaixoides leucogaster (Musophagidae) from Tanzania

Metacheyletia ngaii n. sp. (Acariformes: Cheyletidae) is described from quills of Corythaixoides leucogaster (Ruppell, 1842) (Cuculiformes: Musophagidae) from Tanzania.

Few data are known on biology of these mites, and suggestions concerning their mode of life are controversial. Atyeo et al. (1984) believed that these mites are predators because their movable cheliceral digits are too short to penetrate the quill wall, pierce the quill wall and reach live tissues of a host. Bochkov and Fain (2001) considered these mites parasitic based on morphological characters such as the short tarsi of legs I-III, the absence of legs IV, the short and nude eupathidia of the palpal tarsus and the relatively small sizes of the gnathosoma and suggested that Metacheyletia spp. use the orifices in quill walls which were made by adult syringophilids.
In this paper, we describe a new species of this genus from Corythaixoides leucogaster (Rüppell, 1842) (Cuculiformes: Musophagidae) from Tanzania. A key to females of all known species of the genus Metacheyletia is provided.

MATERIALS AND METHODS
Mites were mounted in Hoyer's medium. Drawings were made with a phase contrast Leica microscope with a camera lucida and DIC optics. In the descriptions below, the idiosomal setation follows Grandjean (1939) as adapted for Prostigmata by Kethley (1990). The nomenclature for leg setae follows that of Grandjean (1944). In predaceous cheyletids of the above listed genera, species diagnostic is mostly based on females, because males are rarely recorded and known just for a few species. All measurements are in micrometres (µm). The scientific names and classification of birds follow Clements (2007).
Type deposition -All material is deposited in the Zoological Institute of the Russian Academy of Sciences, St. Petersburg, Russia.
Etymology -This new species is dedicated to the Maasai God -Ngai, the creator of everything.
Differential diagnosis. This new species is morphologically closest to M. degenerata. In females of both species, three pairs of aggenital setae are present and the propodonotal shield is indistinct. It differs from M. degenerata by the following features. In females of M. ngaii n. sp., setae vi are two times shorter than ve, setae d2 are two times shorter than d1, setae h1 and h2 are subequal, setae c1, d1, and e2 are 130, 115-120, and 75-80 long, respectively. In females of M. degenerata, setae vi are 1.1-1.2 times shorter than ve, setae d1and d2 are subequal, setae h1 are about 1.3 times shorter than h2, setae c1, d1, and e2 are 65, 60, and 50 long, respectively.
Remarks -The genus Metacheyletia is, probably, initially associated with parrots, because its representatives inhabit these hosts in Africa and South America. Unfortunately these mites are unknown from Australia, and records of Metacheyletia spp. from the Australian parrots would be very desirable as an additional prove of this hypothesis. The two species of this genus from non-parrot hosts, M. degenerata and M. ngaii, are still known exclusively from central Africa and morphologically very close to each other. Parrots are widely distributed in central Africa and, therefore, we suggest that in this region, mites of the genus Metacheyletia shifted on a non-parrot host from a parrot with the following dispersion and speciation on birds of different nonparrot orders.