Epsteinius translucidus Lin

Lin, Yu-Chi, Braby, M. F. & Hsu, Yu-Feng, 2020, A new genus and species of slug caterpillar (Lepidoptera: Limacodidae) from Taiwan, Zootaxa 4809 (2), pp. 374-382: 376-379

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Epsteinius translucidus Lin

sp. nov.

Epsteinius translucidus Lin   , sp. nov.

( Figs 1–4, 11 View FIGURES 1–12 , 13, 14 View FIGURES 13–16 , 17 View FIGURES 17–18 , 29, 30 View FIGURES 19–33 , 36, 37, 45, 46 View FIGURES 34–46 )

Material Examined. Holotype ( Figs 1, 2 View FIGURES 1–12 ). ♂ ‘ TAIWAN: NANTOU Co., Xitou , 1100m, 21.VII.2015, reared from Camellia sinensis   ( HSU 15 View Materials G16M), pupated 23.VII.2015, emgd. 16.VIII.2015, Y.C. Lin and R. J. Lin’ [white label, printed]   , ‘ Holotype Epsteinius translucidus   Lin’ [red label, printed] ( NHM)   .

Paratypes. 2 ♂, 6 ♀. 1 ♂ labeled similarly to holotype but with date ‘ 25. VI.2013 ’, ‘( HSU 13 View Materials F15M)’ and ‘emgd. 19.VII.2013   ’; 1 ♂ labeled similarly to holotype but with date ‘ 19.IX.2018 ’, ‘( HSU 18 View Materials J30M)’ and ‘pupated 5.X.2018   , emgd. 19.X.2018 ’; 1 ♀ labeled same as holotype; 2 ♀ labeled similarly to holotype but with date ‘ 19. IX.2018 ’, ‘( HSU 18 View Materials J30M)’, and ‘pupated 30.IX.2018   , emgd. 24.X.2018 ’ and ‘pupated 8.X.2018, emgd. 3.XI.2018 ’; 3 ♀ labeled similarly to holotype but with date ’ 18. VI.2019 ’, ‘( HSU 19 View Materials F41M)’, and ‘emgd. 20.VII.2019   ’, ‘emgd. 24.VII.2019 ’, and ‘emgd. 6.VIII.2019 ’ ( NTNU)   .

Description. Male ( Figs 1, 2, 11 View FIGURES 1–12 , 36, 37 View FIGURES 34–46 ): Head: frons hairy, brown; eyes semi-oval, grey with black center; labial palpus porrect, with 2 nd segment pointed upwards and 3 rd segment short, orange with brown patch; galeae small, partially covered by labial palpus; antenna filiform. Thorax: dark brown dorsally, pale-orange ventrally; legs orange with brown scaling, banded by brown on tarsi, hind leg tibia with four slender spurs, two in the middle and two at the end. Forewing: 5.3–5.5 mm long (from base to apex 5.4 ± 0.1 mm, n = 3); upperside orange-brown with irregular dark brown markings, becoming more pronounced towards base, with purple iridescent suffusion (more visible when alive), a broad dark brown submarginal band, scale fringe orange; underside ground color dark grey, broadly pale grey along dorsum, costa orange, a narrow black submarginal band, followed by a narrow orange terminal band, scale fringe orange with grey near tornus. Hindwing: upperside dark grey black, scale fringe grey; underside ground color pale yellow-grey, dorsum broadly grey, scale fringe grey.

Female ( Figs 3, 4 View FIGURES 1–12 , 45, 46 View FIGURES 34–46 ): similar to male, but larger, forewing 5.5–6.6 mm long (from base to apex 6.1 ± 0.5 mm, n = 5). The 5 th tarsomere with a long triangular recessed pad ( Fig. 45 View FIGURES 34–46 ) bearing sensilla and spinules ( Fig. 46 View FIGURES 34–46 ).

Male genitalia ( Figs 13, 14 View FIGURES 13–16 ): Uncus rather short, narrowly pointed, dorsally with few long hairs near base. Gnathos originating high on tegumen, weakly down-curved, fused before middle with short, blunt dorsal process from junction, long slender distal half with sharply down curved tip. Vinculum ventrally ill-defined, membranous. Valva distally narrowing and up-curved, inner surface densely hairy except near base; a long, distally up-curved, band-like process from inner dorsal margin of valva, and below a straight thorn-like process from base of valva; a sacculus-like process from ventral base of valva, consisting of a bulbous base terminating in a large curved gradually tapering horn-shaped spine reaching beyond dorsal margin of valva. Juxta weakly sclerotised. Phallus short, very wide and rounded at base and gradually narrowing to down-curved, strongly sclerotised ventral apex; vesica with two large cornuti, consisting of a more basal folded and apically curved sclerite and a more distal spine-like sclerite from a wide base.

Female genitalia ( Fig. 17 View FIGURES 17–18 ): Anal papillae flat, semicircular; posterior apophyses very long and slender, anterior apophyses very short and stout; lamella postvaginalis a deeply concave spinulose membrane, lamella antevaginalis with a long conspicuously spinulose knob centrally, flanked by a small plate on each side. Ductus bursae gradually widening from ostium, membranous, longitudinally plicate, narrowed before junction with corpus bursae. Corpus bursae ovate, small, half length of ductus bursae, with two large signa, each a convex plate with a row of flat complex teeth across its center.

Immature stages ( Figs 24–33 View FIGURES 19–33 ): Final instar larva ( Figs 26, 27, 31, 32 View FIGURES 19–33 ) 6.5–7.8 mm in length (7.1 ± 0.5 mm without spine length, n = 7), 3.2–4.7 mm in width of A3 (3.9 ± 0.5 mm without spine length, n = 7). Head brown. Body slug-like with no spine on T1; one spine and one seta on a protuberance for each D1 and D2, one spine on a protuberance for SD of T2; two spines on a protuberance for D, one spine each on a protuberance for D2 and SD of T3; two spines on a protuberance for D, one spine on a protuberance for SD of A1–A8; one spine and two setae on a protuberance for D of A9; no spine on A10. Coloration of body semi-translucent whitish-green in early instars ( Figs 24, 25 View FIGURES 19–33 ), becoming semi-translucent green in final instar, some individuals with an indistinct brown patch laterally on A3–A4. Cocoon ( Fig. 28 View FIGURES 19–33 ) spheroid, 5.1–6.0 mm in long axis (5.3 ± 0.5 mm, n = 5) and 3.3–4.2 mm in short axis (3.8 ± 0.3 mm, n = 5), brown. Pupa ( Fig. 40 View FIGURES 34–46 ) 3.9–4.6 mm in length (4.3 ± 0.3 mm, n = 3), 2.2–2.4 mm in width (2.3 ± 0.1 mm, n = 3); pupal eyepiece with a fracture line ( Figs 41–42 View FIGURES 34–46 ).

Etymology. The specific name translucidus   is derived from the Latin word trans, which means through or across, and the Latin word lucidus, which means under light or full of light. The species group name refers to the semi-translucent coloration of the larva, and is a compound descriptive name comprising an adjective combination with the ending of the second name in masculine form to agree with the gender of the generic name.

Distribution. Epsteinius translucidus   is currently known only from montane areas of central Taiwan at an altitude from 800 to 1100 m.

Biology. Larvae have been found on Camellia japonica   L. (HSU 13F16M and 13K14M) and C. sinensis   (L.) Kuntze (HSU 13F15M, 13K13M, 15G16M and 18J30M) ( Theaceae   ) in June, July, September and October. Of the nine larvae reared in captivity, the pupal stage varied from 14–30 days. These observations suggest there are at least two generations annually, with adults emerging in summer (July–August) and again in autumn (October–November).

The larva of E. translucidus   is semi-translucent, and it usually rests on the abaxial leaf surface. Whilst feeding on the underside of a leaf, the edge of the body is almost transparent, making the larva exceedingly difficult to detect. The feeding behavior is also unusual: most limacodid larvae consume the entire leaf, eating the epidermis only in the early instars ( Cock et al., 1987); however, E. translucidus   retains the feeding pattern typical of early instars throughout its entire life and never eats the whole leaf. This unusual feeding pattern results in the leaf having a skeletonized appearance ( Fig. 33 View FIGURES 19–33 ). The final instar larva of E. translucidus   closely resembles the skeletonized leaf and thus presumably relies on crypsis to avoid predation, unlike many other nettle caterpillars that rely on aposematism and an array of conspicuous poisonous spines.

Predation is an important selective pressure and some prey have evolved cryptic coloration to reduce the likelihood of being visually detected and eaten ( Webster et al., 2015). Transparency is a common strategy for aquatic organisms in mid-water environments to mimic the background and to decrease detectability by visual predators ( Kerfoot, 1982; Langsdale, 1993; Tsuda et al., 1998). However, in terrestrial organisms, transparency is a relatively rare adaptation for avoiding predation. Larvae of E. translucidus   appear semi-transparent and rest on the abaxial side of a leaf, and thus, represent an interesting case in which crypsis is based on transparency through its body color, resting behavior, and feeding pattern.


Departamento de Geologia, Universidad de Chile


University of Nottingham


Mykotektet, National Veterinary Institute


National Taiwan Normal University