The oribatid mite genus Macrogena (Acari, Oribatida, Ceratozetidae), with description of two new species from New Zealand

Abstract Two new species of oribatid mites of the genus Macrogena (Oribatida, Ceratozetidae) are described from alpine soils of the South Island of New Zealand. Macrogena brevisensilla sp. n. and Macrogena abbreviata sp. n. differ from all species of this genus by the tridactylous legs and by the comparatively short interlamellar setae, respectively. New generic diagnosis and an identification key to the known species of Macrogena are provided.


Introduction
Macrogena is an oribatid mite genus of the family Ceratozetidae (Acari, Oribatida) which was proposed by  with Macrogena monodactyla  as type species. At present, three species are known 1 : M. crassa Hammer, 1967, M. rudentiger Hammer, 1967 and M. monodactyla  (from the Antarctic region).
During the recent study of oribatid mite fauna of the high alpine zone of several mountain ranges in New Zealand (Central Otago, South Island), we discovered two new species of the genus Macrogena; both species were common and abundant in the collected material. Additionally, we propose a new generic diagnosis for Macrogena, and provide an identification key for all known species of this genus.

Materials and methods
The collection lo cality and habitat for each new species are given in the respective "Material examined" sections.
Specimens were mounted in lactic acid on temporary cavity slides for measurement and illustration. The body length was measured in lateral view, from the tip of the rostrum to the posterior edge of the ventral plate. Notogastral width refers to the maximum width in dorsal aspect. Lengths of body setae were measured in lateral aspect. All body measurements are presented in micrometers. Formulas for leg setation are given in parentheses according to the sequence trochanter-femur-genu-tibia-tarsus (famulus included). Formulas for leg solenidia are given in square brackets according to the sequence genu-tibia-tarsus. General terminology used in this paper follows that of Grandjean (summarized by Norton and Behan-Pelletier 2009). Drawings were made with a drawing tube using a Carl Zeiss transmission light microscope "Axioskop-2 Plus". Images were obtained with an AxioCam ICc3 camera using a Carl Zeiss transmission light microscope "Axio Lab.A1".

Taxonomy
Genus Macrogena  Type species. Macrogena monodactyla  Diagnosis (partially based on data from Hammer 1967). Ceratozetidae with rostrum with medial rectangular ledge formed by two lateral incisions; rostral setae inserted dorsally or dorso-laterally on prodorsum; lamellar and interlamellar setae strong, straight; bothridial setae fusiform or globular; lamellae large, with short cusps, connected by translamella; tutoria and genal teeth long, reach the level of insertions of rostral setae; dorsophragmata fused medially; notogaster with three or four pairs of porose areas; ten pairs of short and thin notogastral setae; five pairs of genital, one pair of aggenital, two pair of anal, and three pairs of adanal setae; legs mono-or tridactylous. Integument. Body color light brown to brown. Body surface punctate (visible under high magnification). Lamellae, epimeral region, pedotecta I and subcapitular mentum with striae.

Remarks.
Macrogena brevisensilla sp. n. differs from all species of this genus by the tridactylous legs.   Integument. Body color light brown to brown. Body surface punctate (visible under high magnification). Lamellae and pedotecta I striate; epimeral region also with longitudinal striae, however it is visible only in dissected specimens.
Type deposition. The holotype and two paratypes are deposited in the New Zealand National Arthropod Collection, Auckland, New Zealand; two paratypes are de-