Four New Species of Larval Charletonia and Leptus (Acari: Trombidiformes: Erythraeidae), with a Checklist of the Two Genera and Their Hosts from China

Simple Summary The bright red color of Erythraeid mites is conspicuous. The Erythraeid larvae are usually ectoparasitic on arthropods and easily observed. Both the genera Charletonia and Leptus are distributed worldwide. Charletonia has 86 species and Leptus has more than 240 species based on larvae, respectively. To date, two species of the genus Charletonia and 11 species of the genus Leptus have been reported from China. Here, four new species, Charletonia rectangia Xu and Jin sp. nov. collected from tropical rainforests in the Guangxi Province and Yunnan Province, Leptus (Leptus) bomiensis Xu and Jin sp. nov. from the Tibet Autonomous Region, where the altitude ranges from 2673 to 3374 m, Leptus (Leptus) longisolenidionus Xu and Jin sp. nov. from jungles in the Hainan Province (Hainan Island), and Leptus (Leptus) striatus Xu and Jin sp. nov. from Xishuangbanna tropical rainforests in the Yunnan Province. We believe that this study will contribute to further research on the taxonomy and phylogeny of the family. Abstract Four new species, Charletonia rectangia Xu and Jin sp. nov., Leptus (Leptus) bomiensis Xu and Jin sp. nov., Leptus (Leptus) longisolenidionus Xu and Jin sp. nov., and Leptus (Leptus) striatus Xu and Jin sp. nov. are described and illustrated based on larvae. All four new species are from biodiversity hotspots, L. (L.) bomiensis sp. nov. from the Eastern Himalayas biodiversity hotspot, while the other three species from the Indo–Burma biodiversity hotspot.

To date, a total of 11 species of the genus Leptus have been reported bas from China, of which only three species have host records and all the hos [13,[36][37][38][39][40].
In this paper, Charletonia rectangia Xu and Jin sp. nov., Leptus (Leptus) and Jin sp. nov., Leptus (Leptus) longisolenidionus Xu and Jin sp. nov., and Le striatus Xu and Jin sp. nov. are described and illustrated based on larvae fro the specimens of the four new species were collected from biological hotspo

Materials and Methods
Moths were collected by a light trip, harvestmen were captured on leave late at night, and other insects were collected using an insect net in the fiel quently preserved in small vials containing 75% ethanol. Erythraeid larval s insects or harvestmen were detached by a fine brush under a stereomicrosco larval specimens were prepared with Oudemans' fluid and mounted in Hoy Figures were drawn with the aid of a drawing tube attached to a Nikon Ecli croscope. The distribution map was prepared with Arcmap 10.3. The term abbreviations are adapted from Bassini-Silva et al. [18,44], Jacinavicius Haitlinger and Saboori [46], Šundić et al. [47] and Xu et al. [48]. Measurem pressed in micrometers (μm). The SD, standard deviation, keeps two decima
Etymology. The new species is named after the rectangular-like shape of the scutum.  Description. Dorsum. Idiosoma is almost oval (the holotype was used for drawing and its posterior cuticle was broken during slide preparation), with 148 barbed setae (fD = 148-150 in paratypes) ( Figure 6A). Scutum length slightly shorter than width, with two pairs of sensilla (ASE and PSE), and two pairs of scutalae (AL and PL); anterior margin concave, anterolateral margins slightly cambered, posterolateral margins sinuous, posterior margin somewhat convex ( Figures 7A and 8). ASE bases are slightly posterior to the level of AL bases, PSE near the posterior margin of the scutum. ASE, PSE, AL and PL are all entirely barbed, and PSE much longer than ASE, AL and PL subequal ( Table 2). Insects 2022, 13, x 9 of 27        Diagnosis (larva). ASE and PSE with fine barbs throughout the length; gnathosoma with two hypostomalae; palpfemur and palpgenu each with one barbed seta on the dorsal surface (PaScFed and PaScGed); fD = 148-150; Ti I 206-212; Ti III 251-264.
Etymology. The new species is named after a distinctly long solenidion on Ta I.        (Figures 12A and 13); P longer than ASE; PL slightly longer than AL, both entirely barbed (Table 3).  Description. Dorsum. Idiosoma with 52-56 barbed setae (fD = 52 in holotype) ( Figure 17A). Scutum length is slightly longer than the width (Table 4), the anterior margin is concave, anterolateral margins and posterolateral margins are slightly sinuous, posterior margin concave ( Figure 18A); with longitudinal striations on both sides, and small disordered striations in median region ( Figures 18A and 19A); with two pairs of sensilla (ASE and PSE) and two pairs of scutalae (AL and PL); ASE located between AL and PL bases and almost at same level of PL; PSE near posterior margin of scutum; ASE and PSE with fine barbs throughout the length, PSE slightly longer than ASE; PL slightly longer than or subequal to AL, both entirely barbed (Table 4)  Venter. All ventral setae, including coxalae, barbed and acute ( Figure 17B). Coxae I, II and III ventrally with numerous fine striations ( Figure 17B). Two barbed intercoxal setae present between coxae I (1a) and between coxae II (2a), respectively. Four intercoxal setae (3a 1 and 3a 2 ) between coxae III with 3a 1 somewhat anteriorly located; 3a 2 distinctly longer than 3a 1 , 1a longer than 2a, 2a and 3a 2 subequal (Table 4). Three pairs of coxalae (1b, 2b and 3b), 1b much longer than 2b and 3b, 2b and 3b subequal, 1b and 1a almost subequal (Table 4). Area behind coxae III with 18-20 setae (fV = 18 in holotype).
Gnathosoma. With one pair of nude galealae (cs), two pairs of hypostomalae (as and bs), as nude and bs barbed ( Figure 18); bs much longer than as, bs longer than cs (Table 4). Palpfemur and palpgenu with numerous fine striations, and each with one barbed seta on dorsal surface (PaScFed and PaScGed) (Figures 18C and 19C). Palptibia with two barbed setae and one nude seta, ventral surface with one barbed seta, odontus simple. Palptarsus with eight setae, of which five barbed, one nude, one solenidion (ω) and one eupathidium (ζ) ( Figure 18D). fPp = 0-B-B-2BN-5BNωζ. Cheliceral base dorsally with numerous longitudinal sinuous striations; ventral of basis capituli proximally with transverse striations and distally with numerous fine longitudinal striations ( Figures 18B,C and 19B,C). Palpal supracoxal seta (elcp) peg-like.             provide valuable biological information for the study of erythraeid fauna, a phylogeny of the family, and co-evolution with the hosts.

Discussion
The genera Charletonia and Leptus are distributed worldwide (except Antarctica) with 86 and more than 240 species described with larvae, respectively. However, only three species of Charletonia and 14 species of Leptus were reported from China ( Figure 22). Charletonia and Leptus in China represent less than 4% and 6% of the known world species, respectively. It suggests an urgent need to collect and study these genera and even the Erythraeidae in China.