INTRODUCTION

The springtail family Tomoceridae (Collembola) contains 166 species in 16 genera over the world (Janssens 2010). The rare tomocerid genus Lethemurus was described by Yosii (1970) based on the type species Lethemurus finitimusYosii, 1970 from Japan. Yosii (1970) also recombined Tomocerus (Tritomurus) missusMills, 1940 with Lethemurus missus (Mills) that had been described from the USA. Presently, two species in this genus are known in the world.

In this study, we describe a new species of Lethemurus from Korea. Comparison of diagnostic characters between congeneric species is provided with a key to the species.

MATERIALS AND METHODS

Specimens were collected using aspirator and brush and preserved in 80-100% ethanol in 10-20 mL glass vials. Dissection, slide preparation, and observation were conducted using same methods as described in Chang et al. (2015).

Materials of the new species are deposited in the Korean Institute of Biospeleology (KIB) in Daejeon, Korea. The following materials of the congeneric species were also examined: Lethemurus missus (Mills): 1 female, Paulter Cave, Monroe CO, Illinois, USA, SJ Taylor & FN Soto-Adames, 14 ix 2009, Natural History Survey Collection, University of Illinois (Urbana-Champaign).

TAXONOMIC ACCOUNTS

Genus LethemurusYosii, 1970

LethemurusYosii, 1970 (Type species: Lethemurus finitimus

Yosii, 1970; Type locality: Nakatonbetsu Cave, Hokkaido, Japan.

Diagonosis. Eyes absent. Trochanteral organ well developed with ca 40 setae. Base of dentes without large lateral macrochaetae.

Distribution. Korea, Japan, USA.

Lethemurus coreanus Chang and Bae, sp. n.

(Fig. 1-3)

(Korean name: Han-guk-gul-ga-si-tok-to-gi)

Material examined. Holotype: ♂, Gangwon-do, Samcheok- si, Singi-myeon, Daei-ri, Hwanseon-gul Cave (cave NO. 31), 8 i 1974, J Namgung, YG Choi [KIB]. Paratypes: 2♂ (same data as holotype).

Description (Holotype). Body light brown; some parts darker (Fig. 1A). Body size 5.0 mm; antennae longer than body size up to 4.8 mm, 4 times longer than head length (Fig. 2A). Body segment ratio 17 : 9 in thorax, 34 : 38 : 80 : 53 : 28 : 17 in abdomen. Antennae segment ratio 23 : 49 : 308 : 25. Third antennal organ not differentiated. Eyes and PAO absent (Fig. 1B). Head macrochaetae 2+2 / 5+5 / 2+2 (Fig. 2B). Labrum with smooth setae 6 / 5, 5, 4 and 4 spinules on distal margin (Fig. 3A). Chaetae of mesothoracic collar long. Distribution of body macrochaetae as in Fig. 2C. Leg segment ratio (coxa: trochanter: femur: tibiotarsus) 36 : 29 : 66 : 107. Trochanteral organ with 40 setae in trochanter, 35 setae in femur (Fig. 3B). Mid-legs with 1 femoral spine; hind-legs with 2 femoral spines (Fig. 3C). Unguis, unguiculus, and tenent hair ratio 14 : 9 : 8. Unguis with 1 small proximal inner tooth; unguiculus with 3 small teeth from proximal to middle part (Fig. 3D). Tenent hair tapering, acuminate (Fig. 3D). Ventral tube with numerous setae on posterior part (Fig. 3E, F). Retinaculum quadridentate with only 1 seta on corpus (Fig. 3G). Furca ratio 57 : 76 : 11. Dental spines simple form, 8-10 / 2, I, 1, I, 1, I, 1, I without lateral macrochaetae (Fig. 3H). Mucro long and slender, with 3 evenly spaced teeth; basal tooth with a clear membrane (Fig. 3I).

Diagnosis(Table 1). Antennae 4 times longer than head length, almost as long as body length (Fig. 2A). Eyes absent (Fig. 2B). Manubrium without marcochaetae in lateral side (Fig. 3A). Trochanteral organ present with ca 40 setae (Fig. 3B). Unguis with 1 tooth and unguiculus with 3 teeth (Fig. 3D). Dentes with several spines (Fig. 3H).

Etymology. The species epithet “coreanus” is from the country name Korea where the species is described.

Remarks. Type specimens of this species were collected from “Manmulsang” area in Hwanseon-gul Cave, located 200-250 m from entrance, a dark zone with constant temperature.

Key to the species of Lethemurus

Remarks. Key characters of L. missus were examined from the female specimen in Materials and Methods.