New data on the Philippine oribatid mite fauna, with a contribution to knowledge of the genus Drymobatoides (Acari, Oribatida, Mochlozetidae)

A list of identified oribatid mite taxa (Acari, Oribatida) from Capual, Luzon, Mindanao, Polillo, Samal and Samar Islands of the Philippines, including 54 species from 46 genera and 26 families, is presented; of these, 19 species, four genera and one family are recorded in this country for the first time. A new generic diagnosis for Drymobatoides (Mochlozetidae) is proposed. The taxonomic status of the mochlozetid genus Rykella is discussed, resulting in the proposal that Drymobatoides Jacot, 1936 is a senior subjective synonym of Rykella Balogh, 1962 (n. syn.) and in the following reassignments from Rykella: Drymobatoides asiaticus (Yamamoto and Aoki, 2000) n. comb., D. elamellatus (Berlese, 1916) n. comb., D. insignis (Balogh, 1962) n. comb. A new species of Drymobatoides from the Phillippines is described; D. boronganensis n. sp. differs from D. malabaricus (Clement and Haq, 1982) by the morphology of rostral, lamellar and bothridial setae, the length of the interlamellar seta, and the presence of a ventrodistal rectangular incision on leg femur II. An identification key to the seven known species of Drymobatoides is provided.


INTRODUCTION
This work is the final report for our study of the Philippine oribatid mites (Acari, Oribatida) based on a random set of previously unstudied materials, which were received in 2016 from the collections of the Museum of Natural History (University of the Philippines Los Baños). These materials come from the Capual, Luzon, Mindanao, Polillo, Samal and Samar Islands, where oribatids are insufficiently studied (e.g. Corpuz-Raros 1979, 2000, 2014Gruèzo 2005, 2011). Our primary goal is to present a list and new findings of identified oribatid taxa except Carabodidae, Microzetidae, Oppiidae, Rhynchoribatidae and Galumnidae -data on these families were presented earlier (e.g. Ermilov and Corpuz-Raros 2016a-c).
A second goal is to describe and illustrate a new Philippine species of the genus Drymobatoides Jacot, 1936 of the family Mochlozetidae (see Norton and Behan-Pelletier 2009;Schatz et al. 2011) -D. boronganensis n. sp. -and to use this opportunity to rediagnose the genus and assess its relationship with Rykella Balogh, 1962. Drymobatoides was proposed by Jacot (1936) with Drymobatoides mauritius Jacot, 1936 as type species. Currently it comprises three paleotropical species (Subías 2004(Subías , updated 2016, including the type species of its two generic synonyms (=Pelokylla Clement andHaq, 1982, =Seychellozetes Mahunka, 1984). Below we explain why we consider the paleotropical genus Rykella to be yet another junior synonym, and provide an identification key to the now seven known species of Drymobatoides.

MATERIAL AND METHODS
Material -Reported mites were collected from the following sites in the Philippines (extracted from samples by means of Berlese   Methods -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 trochanterfemur-genu-tibia-tarsus (famulus included). Formulas for leg solenidia are given in square brackets according to the sequence genu-tibia-tarsus.
Morphological terminology used in this paper follows that of F. Grandjean: see Travé and Vachon (1975) for general references, Norton (1977) for leg setal nomenclature, and Norton and Behan-Pelletier (2009), for overview.
Drawings were made with a camera lucida using a Carl Zeiss transmission light microscope "Axioskop-2 Plus".
Remarks -Based on data from Mahunka (1994), Seychellozetes benoiti Mahunka, 1984 has movable pteromorph. We could not study the type material of this species, but in Mahunka's original figure (Fig. 17, p. 675), the supposed hinge follows the line of the ventral plate exactly, and we considerbelieve that he confused the lines and was wrong in the observation. This has happened before. For example (pers. com. from Prof. Dr. Roy A. Norton), the mochlozetid genus Uracrobates Balogh and Mahunka, 1967 was originally described as having movable pteromorph and was included in Haplozetidae by Balogh and Mahunka (1967). It became clear that they had made an error in observation, regarding the pteromorph. Mahunka (1988) reillustrated the type species (Uracrobates magniporosus Balogh and Mahunka, 1967), showing clearly the absence of a 'hinge'; he did not specifically state that the pteromorph was immovable, but it is implied. And in Balogh and Balogh 2002 (part 1, p. 300-301) the type species is clearly keyed in a group that is characterized by immovable pteromorph. So, in the case of Uracrobates both original authors indirectly tell us that there was an original error, even if that word was not used. We suspect that the same is true of S. benoiti.
Taxonomic status of Rykella Balogh, 1962 Balogh (1962) proposed the genus Rykella with Rykella insignis Balogh, 1962 from Central Africa as type species. Later, Clement and Haq (1982) proposed the genus Pelokylla with Pelokylla malabaricus Clement andHaq, 1982 from India, andMahunka (1984) described Seychellozetes with Seychellozetes benoiti Mahunka, 1984 from the Seychelles. These three genera are morphologically similar to each other and to Drymobatoides, differing mainly by the number of genital setae (six pairs in Rykella, five pairs in Pelokylla and four pairs in Seychellozetes and Drymobatoides). Balogh and Balogh (1992) proposed that Pelokylla and Seychellozetes are junior subjective synonyms of Drymobatoides without explanation, but they supported the taxonomic independence of Rykella, possibly because of the presence of well-developed lamellar cusps in Rykella (vs. absent in Drymobatoides) (Mahunka 1984). However, Pelokylla malabaricus (see Clement and Haq 1982) and D. boronganensis n. sp. (see below) also have lamellar cusps as in Rykella species. Therefore, if Drymobatoides includes species with four and five pairs of genital setae and some species of this genus have lamellar cusps, then in the absence of other distinguishing features the number of genital setae (six pairs) and the presence of lamellar cusps in Rykella are best regarded as species traits. Since Rykella species match all other traits of Drymobatoides, we propose that Rykella Balogh, 1962 is a junior subjective synonym of Drymobatoides Jacot, 1936 (n. syn.). Hence, the known representatives of Rykella should be recombined in Drymobatoides: D. asiaticus (Yamamoto and Aoki, 2000) n. comb., D. elamellatus (Berlese, 1916) n. comb., D. insignis (Balogh, 1962)  barbed. Bothridial seta setiform, with strong cilia unilaterally and several indistinct barbs on opposite side. About 45 pairs of notogastral porose areas. Epimeral setae setiform, slightly barbed, 1a, 2a, 3a and 4c shorter than other setae. Custodium present, curved laterally. Five pairs of genital setae. Marginoventral porose areas numerous. Leg femur II with rectangular emargination (em) ventrodistally.
Etymology -The specific name boronganensis refers to the Philippine Municipality, Borongan (Eastern Samar Province, Samar Island), where the holotype and some paratypes were collected.
Remarks -Drymobatoides boronganensis n. sp. is morphologically most similar to D. malabaricus (Clement and Haq, 1982) from India in body size (about 700) and in having five pairs of genital setae.