New Perscheloribates species (Acari, Oribatida, Scheloribatidae) phoretic on beetles (Insecta, Coleoptera)

Two new species of oribatid mites of the genus Perscheloribates (Oribatida, Scheloribatidae), phoretic on passalid and zopherid beetles (Coleoptera), are described from the Philippines and U.S.A., based on adults. Perscheloribates paracuriosus n. sp. differs from Perscheloribates curiosus Ermilov, 2016 by the length and morphology of notogastral and adanal setae, the presence of lateral keel-shaped ridge, and the absence of custodium. Perscheloribates parakontumensis n. sp. differs from Perscheloribates kontumensis Ermilov and Frolov, 2019 by the morphology of notogastral setae and the absence of body sculpturing and setae it on leg tarsi I–III.

During taxonomic identification of mites phoretic on passalid and zopherid (Zopheridae) beetles from the Philippines and the U.S.A., we found two new species of Perscheloribates (s.s.). The goal of this paper is to describe and illustrate these new species under the names Perscheloribates paracuriosus n. sp. and P. parakontumensis n. sp.

Methods
Specimens were mounted in lactic acid on temporary cavity slides for measurement and illustration. Body length was measured in lateral view, from the tip of the rostrum to the posterior edge of the notogaster. Notogastral width refers to the maximum width of the ventral plate in ventral view. Lengths of body setae were measured in lateral aspect. All body measurements are presented in micrometers. Some paratypes were dissected and mounted in lactic acid on temporary flat slides. 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.
Drawings were made with a camera lucida using a Leica transmission light microscope "Leica DM 2500".
Type deposition -The holotype and one paratype are deposited in the collection of the University of Michigan Museum of Zoology, Ann Arbor, MI, USA; one paratype is deposited in the collection of the Tyumen State University Museum of Zoology, Tyumen, Russia. All specimens are stored in ethanol with a drop of glycerol.

Leg
Tr Fe Ge Ti Ta  Etymology -The species name paracuriosus refers to the similarity between the new species and Perscheloribates curiosus Ermilov, 2016. Remarks -In the presence of a pointed rostrum, lanceolate bothridial head and developed notogastral setae, and in the absence of prolamella, the new species is similar to Perscheloribates curiosus Ermilov, 2016 from Cuba (see Ermilov & Tolstikov 2016), but differs from the latter by the morphological differentiation of the notogastral setae (c, la, lm short, simple; others distinctly longer, flexible) (versus all setae short, similar in length, simple in P. curiosus), the presence of flexible anal and adanal setae (versus simple in P. curiosus) and a keel-shaped ridge on the lateral side of the prodorsum (versus absent in P. curiosus), and the absence of custodium (versus present in P. curiosus).
Integument -Body color light brown. Body surface punctate (visible under high magnification in dissected specimens). Lateral part of prodorsum slightly microgranulate.
Legs ( Table 2. Seta it present on all tarsi. Famulus of tarsus I short, erect, slightly swollen distally, inserted between solenidion ω 1 and seta ft". Solenidion ω 1 on tarsus I, ω 1 and ω 2 on tarsus II and σ on genu III bacilliform, other solenidia setiform. Material examined -Holotype (female) and three paratypes (one male and two females): , growing on red pine, Pinus resinosa Alton, 1789. Mites were found in pits on the dorsal surface of the elytra. The habitat consists of around 4050 hectares of dense coniferous and mixed hardwood forest on the northeast shore of Lake Michigan. The host beetle is associated with several species of polypore fungi in dense boreal forests in Eastern North America (Evans 2014), suggesting that the normal habitat of this mite species is either on or in the fungal fruiting bodies or in the mycelium growing within the wood of the host tree. Type deposition -The holotype and two paratypes are deposited in the collection of the University of Michigan Museum of Zoology, Ann Arbor, MI, USA; one paratype is deposited in the collection of the Tyumen State University Museum of Zoology, Tyumen, Russia. All Figure 6 Perscheloribates parakontumensis n. sp., adult: a -leg I, right, antiaxial view; b -leg II, without tarsus, right, antiaxial view; cleg III, without tarsus, right, antiaxial view; d -leg IV, left, antiaxial view. Scale bar 50 μm.
specimens are stored in ethanol with a drop of glycerol. Etymology -The species name parakontumensis refers to the similarity between the new species and Perscheloribates kontumensis Ermilov & Frolov, 2019. Remarks -In the presence of pointed rostrum, lanceolate bothridial head with long setiform apex and developed notogastral setae, and in the absence of prolamella, the new species is similar to Perscheloribates kontumensis Ermilov & Frolov, 2019 from Vietnam (see Ermilov & Frolov 2019a), but differs from the latter by the presence of simple notogastral setae (versus with flexible tip in P. kontumensis) and the absence of body sculpturing (versus simple in P. kontumensis) and setae it on leg tarsi I-III (versus absent in P. kontumensis).

General remarks
As previously noted (Norton 1980;Ermilov 2019;Ermilov & Frolov 2019a, b), some oribatid mites are actively phoretic on insects, having morphological adaptations for attachment to the host (for example, gripping setae of beetles between the rostrum of the aspis and the anterior portion of the genital plates in ptyctimous mites, or specifically curved leg claws for holding onto setae of the host as in Siculobata (Paraleius)) (Norton 1980). However, other oribatid species (including P. paracuriosus n. sp. and P. parakontumensis n. sp.) have no visible adaptations, so mostly hold the host's surface by hiding in various depressions and grooves of the host body and using the force of the pretarsal claws for attaching to the surface.
Beetles of the family Passalidae are one of the more common insect hosts actively used by oribatid mites for phoresy (Ermilov 2019), however, phoretic oribatid mites had not been previously reported from A. lamellatus, nor from any beetles of the family Zopheridae. Hence, our findings (P. paracuriosus n. sp. on A. lamellatus and P. parakontumensis n. sp. on P. obcordata) are the first records of the use of A. lamellatus and zopherid beetles by oribatid mites for phoresy.