First records of a blind centipede, Cryptops navis Chamberlin, 1930 (Chilopoda, Scolopendromorpha, Cryptopidae), from Japan

Eight specimens of a scolopendromorph centipede collected in Tokashiki Island and Minamidaito Island (both in the Ryukyu Islands, Japan) represent the first record of Cryptops ( Cryptops ) navis Chamberlin, 1930 from the islands of the Far East (i.e., Japanese Archipelago, Ryukyu Islands and Taiwan). This material also provides new details of the morphological variability of C. ( C .) navis and the first data on natural habitats of C. ( C. ) navis , which previously was known only from soil samples from Singapore and China.


Introduction
The scolopendromorph genus Cryptops Leach, 1814 comprises more than 170 species described worldwide (Bonato et al. 2016) that have been classified into four or five subgenera (Vahtera et al. 2013;Lewis 2016). Lewis (2011) has divided Cryptops sensu stricto into two groups based on the presence of an anterior transverse suture on tergite 1. Subsequently, this author also divided the group lacking this suture into two species groups, doriae and hortensis, based on the presence of one or more saw teeth on the ultimate leg femur.
Cryptops (C.) nigropictus belongs to the hortensis group (Lewis 2011), and C. (C.) japonicus to the doriae group (Lewis 2013) (both having tergite 1 without sutures), while C. (C.) striatus belongs to the group that possesses an anterior transverse suture on tergite 1. In the Ryukyu Islands, all three species were recorded from a montane region of the Okinawa Island (Ômine and Itô 1998).
We recently collected individuals of Cryptops sensu stricto from two islands in the Ryukyu Islands, Japan. Morphological examination indicated that these newly collected specimens certainly belong to the doriae group, and they were identified as C. (C.) navis Chamberlin, 1930, which has never been recorded from the islands of the Far East. Data on the natural habitats of C. (C.) navis are also provided for the first time; previously this species was only found in two soil samples transported to Honolulu (Hawaii) from Singapore (the type locality) and China (without precise location) (Chamberlin 1930(Chamberlin , 1940Lewis 2013) (Fig. 1).

Discussion
The examined specimens were identified as Cryptops (Cryptops) navis based on the following features: 2 + 1 + 2 clypeal setae, one saw tooth on ultimate leg femur and ultimate leg tibia with bifid distal saw tooth, and locomotory legs with a single and comparatively long (nearly half as long as corresponding pretarsus) pretarsal accessory spine (Chamberlin 1930(Chamberlin , 1940Lewis 2013). Although the present specimens possess forcipular coxosternite with 3 + 3 submarginal setae and sternite 21 with broadly rounded corners, which are concordant with the descriptions of both Chamberlin (1930) and Lewis (2013), both the setal arrangement of forcipular  coxosternite and shape of sternite 21 are variable in some Cryptops species (Lewis 2009(Lewis , 2013Schileyko and Stoev 2016).
The Ryukyu specimens differ from previous descriptions (Chamberlin 1930(Chamberlin , 1940Lewis 2013) in the following characteristics: 5-6 (vs 9) prelabral setae on clypeus, 12-23 (vs 32-60) coxal pores, and a longitudinal glabrous (vs setose) area on the ultimate leg prefemur. However, the number of prelabral setae was reported as a variable character in C. (C.) parisi Brolemann, 1920 (Iorio and Geoffroy 2003), and the number of coxal pores is highly variable even intraspecifically (Lewis 1999;Schileyko 2008). The specimens from Tokashiki Island also possess the longitudinal glabrous area on the ultimate leg prefemur, which has been treated as a diagnostic characteristic for some Cryptops species (Lewis 2013(Lewis , 2016. Nevertheless, the ultimate leg prefemur is sparsely setose in the specimen from Minamidaito Island, and the glabrous area was not observable in the holotype (Lewis 2013). Given the fact that the discordant details listed above are known to be variable in the other Cryptops species (even varying among the Ryukyu populations), we consider the present specimens to be C. (C.) navis. The number of prelabral setae and coxal pores, as well as the presence of a longitudinal glabrous area on the ultimate leg prefemur, may represent intraspecific variations of C. (C.) navis.
Only two specimens of C. (C.) navis have been previously reported, and the precise distribution of this species was uncertain (Chamberlin 1930(Chamberlin , 1940Lewis 2013). The studied material, collected under straw close to paddy fields and under fallen leaves near the seashore in Tokashiki Island and Minamidaito Island, respectively, therefore provides the first data on the natural habitats of C. (C.) navis. According to Chamberlin (1930Chamberlin ( , 1940 and the present results, the northern border of the range of this species is Tokashiki and Minamidaito islands, and the southernmost is Singapore (the type locality) (Fig. 1). Because only the holotype of C. sinesicus Chamberlin, 1940 (= C. (C.) navis; see Lewis 2013) was recorded from China (see Song et al. 2010), the precise distribution of C. (C.) navis in China cannot be determined. However, it is possible that the type locality of C. sinesicus is located along the coastline of Southern China, because this species was collected from the small islands within the Ryukyu Islands, and was found in the soil from Singapore.
The present findings revealed morphological variations among the two populations in the Ryukyu Islands, and suggest that these characteristics could be intraspecific variations of C. (C.) navis. However, a detailed understanding of the intraspecific variations of this species remains hampered by a lack of sufficient material from other localities. With the aid of the habitat information of C. (C.) navis in the Ryukyu Islands, further faunal surveys in Southeast and East Asia are necessary to clarify the true range of this species. Then, additional specimens obtained in future surveys will help elucidate the precise intraspecific morphological variations of C. (C.) navis.