Two New Species and a New Combination of the Subfamily Erythraeinae Based on Larval Stage (Acari: Trombidiformes: Erythraeidae) from China

Simple Summary Erythraeid mite members are large, larvae usually parasitize other arthropods, whereas the nymphs and adults are free-living predators of a small insect. Free-living adults/nymphs and parasitic larvae vary greatly in morphology, and classification is usually treated independently. To date, more than 850 species of erythraeid mites have been recorded. Among them, more than 580 species were described only as larvae. Eatoniana Cambridge, 1898 is a small genus within Erythraeidae comprising, 10 valid species worldwide, three species of which were only reported based on larvae. Erythraeus Latreille, 1806 includes 123 species distributed worldwide, with 69 species reported based on larvae alone. Here, two new species, Eatoniana nanlingensis Xu and Jin sp. nov. from Guangdong Province and Erythraeus (Erythraeus) kunyuensis Xu and Jin sp. nov. from Shandong Province, are described based on larval stage. We believe that the study will contribute to further studies on the taxonomy and phylogeny of Erythraeidae. Abstract The species Eatoniana yangshuonicus (Haitlinger) comb. nov. is transferred from the genus Erythraeus to Eatoniana based on the basifemoral setal formula 2-2-1. Two new species, Eatoniana nanlingensis Xu and Jin sp. nov. and Erythraeus (Erythraeus) kunyuensis Xu and Jin sp. nov. are described and illustrated based on larvae. Eatoniana nanlingensis sp. nov. from the Oriental region (Guangdong Province), Er. (Er.) kunyuensis sp. nov. from the Palaearctic region (Shandong Province). An updated key to larval species of the genus Eatoniana of the world is presented.

Mąkol and Sevsay [4] proposed that the genus Abalakeus Southcott, 1994 is a synonym of the genus Eatoniana Cambridge, 1898, and evidence was obtained through the reared individuals. The genus Eatoniana includes 10 species, one of which is a fossil species, E. crinita Sidorchuk, Konikiewicz, Welbourn and Mąkol, 2019 based on active postlarval instars [5], of the remaining 9 species, 3 are reported based on larvae only, 4 on active postlarval instars only and 2 on both larvae and active postlarval instars, respectively [2,4,5].
Venter. All ventral setae, including coxalae, setiform, barbed and with pointed tips ( Figure 1B). Two pairs of intercoxal setae (1a and 3a), 1a slightly longer than 3a (Table 1); 1a located between and slightly posterior to coxae I, 3a almost in a line with anterior edges of coxae III; behind coxae III with 27 setae (28 in paratype), two setae (55-56) between coxae II and III. Three pairs of coxalae (1b, 2b and 3b), 1b much longer than 3b, 3b longer than 2b (Table 1). Length of setae increasing from 67 posterior to 3a to 91 near posterior margin.         Etymology. The name of the new species is derived from the Nanling National Natural Reserve where it was collected.
Etymology. The name of the new species is derived from the Nanling National Natural Reserve where it was collected.
Types Eatoniana nanlingensis sp. nov. can be easily separated from E. chekei, E. gonabadensis and E. lorestanicus based on TFe I without a solenidion (vs. present); the new species can be easily separated from E. plumipes and E. yangshuonicus based on eyes without platelets (vs. present) and two setae present between coxae II and III (vs. absence).
Eatoniana nanlingensis sp. nov. differs from E. bambusae by scutum shape (trapezoidal vs. pentagonal), the shape of ASE and PSE (having fully fine barbs vs. having fine barbs on distal halves), the presence of eupathidium on Ta III (vs. absence), fD (68 vs. 50), fn Ti Scutum with two pairs of sensilla (ASE and PSE) and scutalae (AL and PL). ASE and PSE with fine barbs on distal half, PSE much longer than ASE. AL longer than PL, both entirely barbed ( Table 2).  Description. Dorsum. Idiosoma almost oval or sub-circular, with 33 barbed setae (fD = 32-33 in paratypes) ( Figure 5A). Two pairs of eyes present on platelets. Scutum is pentagonal, anterior margin and anterolateral margin almost straight and posterolateral margin is almost straight with visible concavity between the base of PSE (Figures 6A and 7). Scutum with two pairs of sensilla (ASE and PSE) and scutalae (AL and PL). ASE and PSE with fine barbs on distal half, PSE much longer than ASE. AL longer than PL, both entirely barbed ( Table 2).     Venter. All ventral setae, including coxalae, setiform, barbed and with pointed tips ( Figure 5B). Two pairs of intercoxal setae (1a and 3a) present, 2a absent, 1a longer than 3a; Three pairs of coxalae (1b, 2b and 3b), 1b much longer than 3b and 2b, 3b longer than 2b ( Table 2). Intercoxal setae (1a and 3a) located between coxae I and coxae III, respectively, 1a located between and posterior to coxae I, 3a almost in a line with anterior edges of coxae III; behind coxae III with 14 setae (14 in paratypes).
Etymology. The name of the new species is derived from the National Natural Reserve where it was collected.
Types  Etymology. The name of the new species is derived from the National Natural Reserve where it was collected.
Types. Holotype, larva, unidentified herbaceous plants, collected by Si-Yuan Xu on 21 July 2018, from Kunyushan National Natural Reserve (Altitude: 135 m), Shandong Province, China. Paratypes, three larvae, the same data as the holotype.   In the original description, Haitlinger [25] mentioned Er. (Er.) kacperi with only one seta in BFe III, but figured it with two setae (Figure 8). Moreover, Haitlinger [25] figured Er. (Er.) kacperi with only one pair of eyes (Figure 1), not mentioned in the text, while all other known Erythraeus members have two pairs of eyes. Therefore, it seems that the taxonomic status of Er. (Er.) kacperi needs to be further studied.