REDESCRIPTION OF PARACAROPSIS TRAVISI (BAKER, 1949) (TROMBIDIFORMES: CHEYLETIDAE), WITH RANGE EXPANSION, ADDITIONAL HOST RECORDS, AND REEVALUATION OF CHEYLETID CHAETOTAXY BASED ON THE SEJUGAL FURROW

A lectotype and paralectotype are designated for Paracaropsis travisi, which is redescribed and illustrated. Specimens are reported from additional Laphria hosts in Michigan and leaf litter in Arkansas. After comparision of Nearc- tic and Palearctic specimens, the synonymization of Paracaropsis travisi (Baker, 1949) and Paracaropsis strofi (Samoi ˇ nak, 1956) is upheld. We also review the Grandjean System and reevaluate idosomal setal nomenclature in Cheyletidae based on the sejugal furrow.


INTRODUCTION
Cheyletidae are small (generally 400-700 µm) yellow, orange, or brown mites (Volgin 1969). More than 370 species are known from 74 genera. Many are free-living predators in leaf litter and soil, tree bark, stored food products, and bird, mammal and insect nests, though some are vertebrate and invertebrate parasites or associates (Walter et al. 2009). Species found on vegetation or in stored grain can be important predators of crop pests and graminivorous mites (Hughes"1976;de Moraes et al., 1989). Volgin (1969) erected Paracaropsis for two species, Acaropsis travisi Baker, 1949 and Acaropsis strofi Samšiňák, 1956, which were collected in Georgia (U.S.A.) and Děčín (Czech Republic) from a spiny lizard (Sceloporus) and bee-like robber flies (Laphria flava), respectively. Summers and Price (1970) reillustrated Paracaropsis travisi and synonymized P. strofi with it without giving explicit reasons.
Previous authors illustrated the dorsum and gnathosoma of Paracaropsis travisi only. Improved illustrations of the dorsum and gnathosoma, as well as detailed illustrations of the legs and the first illustration of the venter are provided. Named setae are labeled across all illustrations. In addition, P. travisi is reported for the first time from multiple species of Laphria (Diptera: Asilidae) in Michigan as well as leaf litter in Arkansas.

MATERIALS AND METHODS
Nearctic, including the lectotype and paralectotype of Paracaropsis travisi (Baker, 1949), and Palearctic specimens were examined. The holotype of P. strofi (Samšiňák, 1956) could not be located as "[s]ome of Samsinak's slides survive, but many were presumably kept in his private collection. Nobody can trace them now" (Klimov, pers. comm. December 2012). Only Nearctic specimens were measured and reported as future genetic work may resurrect P. strofi as a valid species.
All measurements are listed in micrometers: lectotype given, followed by range of Nearctic material in parentheses. Range measurments are composed of the one paralectotype, as well as 19 specimens from Arkansas and Michigan. Palaearctic specimens were excluded from the measurements due to the possibility of P. strofi being resurrected in the future. Large stippling indicates unsclerotized arthrodial membrane.
Specimens were mounted in Hoyer's medium and viewed using both phase and differential interference contrast microscopy. Illustrations were made from the lectotype with confirmation of structures on the Arkansas specimen by methods outlined by Fisher and Dowling (2010).
The lectotype and paralectotype are deposited in the National Mite Collection, National Museum of Natural History, Smithsonian Institution, Beltsville, Maryland. The specimen collected in Arkansas is deposited in the Acarology Collection at the University of Arkansas. The specimens collected in Michigan and Russia are deposited in the Museum of Zoology at the University of Michigan.

TERMINOLOGY
An effort was made to implement terminology that is broadly accepted and used across acariform mites, despite conventions among cheyletid workers as some terms used in cheyletid literature are innacurate or synonymous with other terms used more broadly across acariforms. We therefore follow the suggestions outlined by Fisher et al. (2011) and expanded by Skvarla et al. (2014), with some modifications, which are outlined below.
Hypostome has sometimes been used synonymously with subcapitulum, however it more accurately refers to the area of the subcapitulum anterior to the oral opening and not to the entire structure (Evans, 1992;Krantz, 2009).
Within Cheyletidae, two pairs of relatively long anterior gnathosomal setae have historically been referred to as adoral setae (ao1-2) (e.g., Goff, 1982;Bochkov and Klimov, 2005;Xia et al., 2011). Di Palma et al. (2009), however, identified two pairs of minute setae at the anterior tip of the gnathosoma as the adoral setae. These minute setae are present in Paracaropsis travisi and are therefore identified as adoral setae. The homologies of the setae previously identified as ao1-2 and the subcapitular setae previously identified as n are unknown. We therefore refer to them by position: dorsal subcapitular setae (ds, =ao2 of previous authors), ventral subcapitular setae 1 (vs1, = ao1 of previous authors), and ventral subcapitular setae 2 (vs2, = n of previous authors).
Idiosoma -Terminology for idiosomal structures (i.e., setae and plates) across Acariformes has been heavily debated and remains contentious. The dominant system used by most acarologists is called the Grandjean System, but this system is contested. In general, we follow Grandjean (1939Grandjean ( , 1944 as implemented by Kethley (1990) for dorsal setae, but with significant modifications discussed below.
The Grandjean System -Based upon his studies in comparative arachnology, van der Hammen (1963) hypothesized that the acariform body comprised 14-17 body segments (6 prosomal and 8-11 opsithosomal); he also proposed that the opisthosoma had overgrown the metapodosoma dorsally.
Building upon van der Hammen's ideas, Grandjean (1970) proposed that the propodosoma is also overtaken dorso-anteriorly by an outgrowth of the gnathosoma, which he termed 'aspidosoma'. Under this hypothesis, the opisthosoma contains ten segments and begins immediately posterior to the sejugal furrow with the first segment 'C'. Dorsal setae are named according to their corresponding segment, so that the setae on segment C are named c1, c2, c3, etc. Grandjean especially applied his hypothesis to Oribatida, although it was later adapted to Caeculidae (Coineau ,1974), and currently it has gained popularity across disparate acariform taxa (e.g., Erythraeidae: Mąkol, 2010;Penthalodidae: Jesionowska, 2010;Tydeidae: Kazmierski, 2008). Weigmann (2001) pointed out that there is no evidence for such overgrowths of the gnathosoma and opisthosoma, and instead argued for reimplementation of Grandjean's previous systems (since 1934) that acknowledged the dorsal appearance of the podosma and therefore identified the first two segments posterior to the sejugal furrow as metapodosomal. Recent studies by Barnett andThomas (2012, 2013) investigating the embryology of the oribatid Archegozetes longisetosus Aoki, 1965 further call into question the Grandjean System. Those studies demonstrate the opisthosoma of A. longisetosus comprises only two segments (not 10), firmly refuting van der Hammen's (1963) segmentation hypothesis and therefore Grandjean's (1970) amendments. Unfortunately, their investigations are as yet unable to determine what happens to the podosoma dorsally during development, and therefore cannot currently address terminology of dorsal setae.
Ultimately, the matter will be resolved only after detailed investigation into the developmental biology of a number of disparately related acariforms. Therefore, it has been suggested (Fisher et al., 2011) that until that point, hypothesisdependent terminology (i.e., 'aspidosoma' and 'opisthosoma') should be avoided in favor of hypothesis-independent terminology. Thus, Fisher et al. (2011) suggested re-implementing the historically favored 'hysterosoma' (body posterior to the sejugal furrow) and proposed increasing the use of 'proterosoma' (body anterior to the sejugal furrow), even though the latter is more inclusive than necessary (i.e., 'proterosoma' includes the gnathosoma). Since then, the sejugal furrow has been recoginized as a key synapomorphy uniting acariform mites with camel spiders (Solifugae) into a clade called Poecilophysidea (Dunlop et al., 2012), which is supported by large molecular datasets (Dabert et al., 2010, Pepato et al., 2010 and characteristics of the reproductive system (Alberti 1980a(Alberti , b, 2000Alberti and Peretti, 2002;Klann et al. 2009). Therefore, as noted by Skvarla et al. (2014), terminology focused on the sejugal furrow (i.e., 'proterosoma' and 'hysterosoma') is no longer hypothesisindependent, but is based on well-supported hypotheses about acariform relationships. Therefore, we continue with the suggestion of Fisher et al. (2011), with the modified rationale of Skvarla et al. (2014), and herein use 'proterosoma' when referring to the dorsal idiosoma anterior to the sejugal furrow and 'hysterosoma' when referring to the dorsal idiosoma posterior to the sejugal furrow.
'Prosoma' (podosoma + gnathosoma) has been incorrectly used by some cheyletid workers (e.g., Volgin 1969) to refer to the body anterior of the sejugal furrow, thus failing to include the metapodosoma. Therefore, 'prosoma' is not a viable alternative for this discussion.
Cheyletidae chaetotaxy -hysterosoma -Many chyletid authors have also adopted the Grandjean System for idiosomal setae. However, setae on segment C (i.e., c1 and c2) are consistently identified as anterior to an obvious fold between Leg II and Leg III (e.g., Kethley, 1990;Bochkov et al., 2006;Xia et al., 2011). It is possible that such authors are proposing the dorsal fold is not the sejugal furrow, but we have not found evidence of this discussion. Under the Grandjean System, segment C is defined as the first opisthosomal segment, which is immediately posterior to the sejugal furrow dorsally. This change is additionally supported by evaluation of h2, which is a ventral element occurring near cupule ih across acariforms. Previous implementation of the Grandjean System within Cheyletidae placed h2 dorsally and distant from ih. By moving the C-setae posteriorly, we propose only h1 is present dorsally and h2 is absent, which is supported by no accompanying seta to cupule ih.
Herein, we make the following terminological suggestions with regard to the hysterosoma. First, until hypotheses of cheyletid body organization confirm the presence of a non-sejugal dorsal furrow, we identify the sejugal furrow in Cheyletidae as the primary fold visible dorsally, and therefore reject the use of C-segment terminology anterior to this furrow. Second, given the widespread use of the Grandjean System in Acariformes, regardless of the legitimacy of hypotheses therein, we see no need to implement new terminology for idiosomal setae at this time. Furthermore, we suspect these setae are homologus across acariforms, hense we do not endorse alternate systems such as Fain (1979), and continue with c1, c2, d1, e1, etc. In summary, we identify setae immediately posterior to the sejugal furrow as C-setae (instead of D-setae) and rename hysterosomal setae accordingly.
Cheyletidae chaetotaxy -anterior idiosoma -Although proterosomal terminology among acariforms is also much contested, we follow the system implemented Granjean's (1939Granjean's ( , 1944, which identifies verticals (vi, ve) and scapulars (sci, sce). These designations are already widely used among cheyletid workers and we continue them herein. However, our reevaluation of C-setae (see above) renders previously named setae on the posterior proterosoma neotrichous. One pair of these neotrichous setae has been previously identified by Fain (1979) as a humeral seta; however, we refer to this seta as hm instead of h in order to avoid confusion with the h setae of the hysterosoma. Additionally, two pairs of setae preiviously identified as C-setae (d1 and d2 in the Fain system) seemingly represent homologous neotrichy across cheyletoids, although correlaries in other acariforms have not been identified. Because of this homology across cheyletoids, we would prefer to be consistent with their terminology (i.e., continue d1/2). However, d1/2 is already used in reference to hysterosomal setae in the Grandjean System. Therefore, we suggest renaming these setae x1 and x2 ("x" refers to unknown homology and is used because of disuse in other terminological systems) until homology assessment can be made across taxa.
Paracaropsis VOLGIN 1969 Review -Volgin (1969) erected Paracaropsis for two species of Acaropsis, viz. P. travisi (Baker, 1949) and P. strofi (Samšiňák, 1956). Summers and Price (1970) redescribed and reillustrated P. travisi from the type specimen; they showed that, unlike in the original illustrations, the posterior plate is present and setae sce, c2, d1-2, e1-2, and f1 are on minute platelets. Summers and Price also synonymized P. strofi with P. travisi; they gave no express reasons for this, though presumably based the synonymization on the presence of the posterior plate and setae on platelets in P. travisi and the fact that there were only two species known in the genus. Diagnosis -Palp claw with 7-9 teeth. Palp tarsus with 1 comb, 2 sickle-shaped setae; comb with ca. 14 teeth. Eyes present. Proterosomal shield extending onto hysterosoma, capturing c seta. Plate bearing no setae present between d1 and e1. Plate bearing h1-3 present. Dorsal body setae (except c2) short, slightly serrate. Setae c2 long, smooth.
Male and immature stages. Unknown.

DISCUSSION
The holotype and paratype specimens were mounted under the same cover slip, which was not ringed. This resulted in the mounting medium drying and cracking to the point that the specimens were nearly impossible to see. In addition, it was not possible to determine which specimen Baker intended to be the holotype or paratype. The authors have thus remounted the specimens on separate slides and designated the lectotype and paralectotype. Klimov (1997) stated Palaearctic and Nearctic specimens of Paracaropsis travisi sensu Summers & Price, 1970 (=travisi+strofi) differ by the relative position of the c setae: in Palaearctic speciemens the distance between these setae is subequal to the length of the setae, while in Nearctic specimens the distance is shorter than the length of the setae. This is true for the holotype of P. travisi and examples of Paelarctic P. travisi examined; however, additional Nearctic specimens examined exhibit this range of variation within a population collected at a single field site. We therefore recognize the synonymization of P. strofi with P. travisi.
Paracaropsis travisi has previously been reported from a Palaearctic bee-like robber fly, Laphria flava. The records reported here expand the known hosts to five other Laphria species, viz. L. postica, L. index, L. royalensis, L. janus, and L. flavicollis, demonstrating P. travisi utilizes a wide range of Laphria. Klimov (pers. comm., Feb. 2013) indicated that "Paracarop-sis can be found between the midcoxae of Laphria" and that "they are pretty common".
The lectotype and paralectotype may have been collected from Sceloporus woodi, a phrynosomatid lizard, in the Nearctic. This is questionable given the prevelance Paracaropsis on Laphria and because the original slide label has a question mark after Sceloporus woodi, suggesting Baker was unsure of some aspect of the information. Additionally, S. woodi is not known from Georgia; if the Paracaropsis were indeed collected from a spiny lizard, it was likely S. undulates, not S. woodi. However, given the length of time since the original collection and lack of additional information, until further collections reveal otherwise, definintive conclusions cannot be made.
Finally, one specimen was extracted from leaf litter in Arkansas by the authros using Berlese extraction. Additional specimens have not been found after processing more than 400 gallons of leaf litter from the same and similar localities. Why that specimen was in leaf litter is unknown. However, several species of Laphria are abundant at that site (Devil's Den State Park, Ark.), which at least does not refute the hypothesis of an association with Laphria. Further investigations into the association of Paracaropsis and Laphria, including how the mites find their hosts, may shed light onto this.