Eustra Schmidt-Gobel 1846
Creators: name: Fedorenko, D. N.
Publisher: name: Zenodo
Year: 2019
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Carabidae
Eustra

description: Genus Eustra Schmidt-Göbel, 1846
Schmidt-Göbel, 1846: 65; Chaudoir, 1854: 309; 1868: 71; Andrewes, 1919: 295, 299; 1929: 163, 167; Bänninger, 1927: 189, 206; Jeannel, 1946: 48; Stork, 1985: 1121, 1123; Deuve, 2001: 547–578; Moore et al., 2011: 63–82 (larva).
Type species: Eustra plagiata Schmidt-Göbel, 1846 (by monotypy).
REDESCRIPTION.Body (Figs 1–6) macropterous, small, BL ca 2.5–4 mm in general, shiny or slightly dull, and rather pale, yellow or pale brown; elytra bimaculate, i.e., each with a darker, subquadrate, submedian macula. Dorsal microsculpture meshed, isodiametric, very superficial to obliterate; elytra laterally with aciculate microsculpture consisting of dense microscopic tubercles. Body appendages and underside rather densely pubescent; dorsal pubescence sparser, its density depends on head, pronotum or elytra, leaving elytral submarginal area glabrous; propleura generally smooth.
Head medium-sized, more or less constricted behind eyes, without fixed supra-ocular setae. Eyes round in lateral view, small and convex; genae distinct, oblique, neither toothed nor embracing eyes from behind. A well-developed ocular ridge running around and at a distance from eye; the ridge conspicuously edged anteroventrally, separating gena from maxillary fissure; dorsally it consisting of supra-antennal carina anteriorly and supra-ocular carina behind, the former running just inside the latter, with a strigose area mostly substituted for both at anterior margin of eye. Frontal foveae missing. Clypeus bisetose on each side, slightly transverse, subquadrate, gently sinuate apically; frontoclypeal suture mostly subsinuate. Labrum long trapezoidal, almost triangular, with sides straight to subsinuate and converging much apicad; apex rounded to truncate, tuberculate or crenulate, with eight close setae along apical margin and one preapical seta on each side of inner pair of setae; without or with a subtle emargination on each side of two median setae. Antennae rather short, moniliform, entirely pubescent; pilosity on antennomeres 1–4 similar to that on the rest. Scape globular, short, with or without dorsal seta, pedicel eccentrically articulated. Antennomeres 5–10 subglobose and increasingly, slightly to moderately, transverse, antennomere 11 parallel-sided, twice as long as wide and as long as antennomeres 8–10 combined.
Mandibles moderately long, scrobe with 0–2 setae along ventral ridge; terebral tooth small, retinacular ridge large, bifid, basal retinacular tooth triangular, blunt, without narrow basal extension. Mentum anteriorly bisetose, with vestigial median tooth; ligula subquadrate, quadrisetose, paraglossae adnate vestigial. Submentum quadrisetose, gula well-developed, moderately wide basally, almost indistinct at submentum. Maxillary cardo short, stipes bisetose. Terminal labial and maxillary palpomere fusiform, maxillary one twice as wide as penultimate palpomere. Penultimate labial palpomere with two very close setae.
Pronotum cordate, more or less transverse, broadest 1/3– 1/5 from apex. Base slightly narrower than apex, truncate, strongly and abruptly oblique on sides; basal angles sharp, obtuse to right. Apex deeply sinuate or subtruncate medially, apical angles acute and porrect. Sides rounded, subsinuate just behind apical angles and straight to sinuate before basal ones. Disc convex, lateral margin rather widely explanate and finely beaded, more or less reflexed basally; lateral edge setulose and tuberculate or crenulate to smooth. Basal foveae round and deep, occupying basal third, median line fine yet deep, basal transverse impression quite transverse and fairly deep, apical transverse impression less so.
Elytra estriate, wide, convex, broadest behind middle, with sides more or less rounded and diverging slightly apicad, more rounded behind humeri, obliquely truncate posteriorly; apices rounded separately each; lateral half of each elytron flattened and longitudinally impressed in third fourth to middle third. Base distinctly wider than that of pronotum, basal margin slightly oblique from humeri to mesothoracic peduncle; humeri prominent, with blunt or rounded apices. Basal ridge fine at humerus, vestigial inside; lateral reflexed margin narrow, interrupted before preapical plica; lateral edge setulose and almost indistinctly serrulate, sometimes (E. nageli subglabra ssp.n.) smooth and nearly glabrous. Epipleura totally reduced behind preapical plica. Dorsum densely tuberculate and pilose, except for a smooth and glabrous submarginal area in middle third; pilosity dense to sparse, moderately long to very short. Fixed dorsal setae, basal or discal, missing; submarginal umbilical seta series (USS) continuous, consisting of larger setigerous pores, about ten (9–13) in basal 2/3 and five on a level with and behind preapical plica, the anterior and posterior pore groups being connected by an oblique row of 3–7, mostly 4–5, smaller setigerous pores. — Anterior setigerous pores increased to 11–13 in number are due to the presence of a few minute pores additional to larger ten.
Underside: mesocoxae separate and slightly projecting, with ventral intercoxal bridge, chiefly posterior process of mesoventrite, totally reduced, leaving mesocoxal cavities shallow, more so mesally, and apodemal pits of mesofurca (mesendosternite) exposed; anterior metaventral process either somewhat pointed, tuberculate and projecting (E. cariniceps sp.n.) or apically blunt to truncate, not or barely projecting (the other congeners reviewed). Metacoxae separate. Abdominal sternites transversely sulcate at bases (which character is hardly traceable because of the sternites telescoped), with obligatory setae hardly separable from dense ventral pubescence if at all (four or more longer setae present closer to apical margin), sternite VII mostly bisetose on each side.
Legs. Chetome obscured by dense, longer and shorter, pilosity. Meso- and metatarsomere 1 long, as long as respective tarsomeres 2–4 combined, usually slightly to conspicuously longer than tarsomere 5. Protarsomeres 1–3 ventroapically rounded and setose; protarsomeres 1–2 barely dilated, with ventral pad, in male.
Aedeagus as in Figs 7–46; right paramere narrow, longer to shorter than left one; right paramere more or less densely setose, left paramere glabrous. Internal sac mostly with a cluster of ca 5–7, strong, spiniform, radiating apical sclerites.
Female genitalia and reproductive tract. Gonocoxae entire, membranous and densely pubescent, widely separated by a round sclerotized part of bursa copulatrix; helminthoid sclerite well-developed.
DIAGNOSIS. The genus is very distinctive within Ozaenini in many points (see also ‘Comments’ to the genus). Very small body size and pale brown ground-colour, combined with fusiform terminal palpomeres, separate Eustra and Dhanya Andrewes, 1919 from the other ozaenines. The two genera are otherwise very distinctive. Specifically, Eustra is readily distinguishable from Dhanya in having mesocoxae conspicuously separated (vs. contiguous) and propleural pits missing (well-developed propleural pits are autapomorphy of Dhanya within Ozaenini). The other differences of Eustra from Dhanya are many: ocular ridge well-developed throughout or nearly so (vs. indistinct posteriorly), clypeus transversely subquadrate and bisetose on each side (vs. long hexagonal and unisetose on each side), antennal scape globulose (vs. short subcylindric), antennomere 11 much longer, labrum trapezoidal (vs. subquadrate), mandibles medium-sized and incurved (vs. large and almost straight), mandibular scrobe with several setae in general (vs. asetose), gula well-developed (vs. totally reduced), submentum bisetose (vs. unisetose), mentum tooth indistinct (vs. well-developed), maxillary stipes bisetose (vs. unisetose), pronotal lateral edge setulose and crenulate or tuberculate (vs. smooth, with 3–4 subequally spaced setae inside), elytral epipleura missing apically (vs. entire), elytral discal setae missing (vs. multiple in sites of intervals 3 and 5), protarsomeres 1–3 ventroapically rounded (vs. toothed at each apical angle), protarsomeres 1 and 2 slightly dilated and with ventral pad in male (vs. not dilated and without ventral pad), mesotarsomere 1 longer, as long as mesotarsomeres 2–4 combined (vs. as long as those 2 and 3 combined), metatarsomere 1 much longer than (vs. as long as) metatarsomere 5, abdominal sternite VII membranous yet entire apically (vs. well sclerotized, being sinuate in female in addition), with 2 apical setae on each side in general (vs. 3–4 setae on each side), female gonocoxite IX membranous (vs. well sclerotized). Finally, the genus has ventral structure of pterothorax unique within Adephaga.
DISTRIBUTION. The range extends throughout the Oriental region from Sri Lanka, southern India and Nepal, through Indochina to Taiwan, southern China, southern Japan, the Sunda Isles and the Philippines, including also adjacent parts of Palearctic East Asia in eastern China, Korea and Japan.
HABITATS AND HABITS.The members of the genus are silvicolous or cavernicolous. Silvicoles were captured at elevations ranging between 60 and 1,900 m a.s.l. Many of them are known from one to a few specimens only and rare in collections. On the other hand, most species taken by me in Vietnam are not uncommon lowland and piedmont forest-dwellers. Great majority of the specimens were captured by hands under bark of larger dead trees, standing or fallen, or under tree fragments on the ground (E. csikii) at elevations below 800 m a.s.l. The species were found to be associated with ants and/or termites, with two or three of them sometimes sharing their habitats with one another and often also with such carabids as Dhanya bioculata Andrewes, 1919 (Ozaenini), Perigona spp. (Perigonini), and Morion spp. (Morionini).
COMMENTS. The above redescription only concerns non-cavernicolous species reviewed below.
Ventral pterothoracic structure of Eustra is worthy of special mention. Even though this pattern looks very primitive, it with no doubt has emerged from much more complex structure in course of evolution. This latter groundplan is peculiar to nearly all Adephaga and includes almost internally contiguous mesocoxae, ventrally bridged with posterior process of mesoventrite and anterior process of metaventrite. These two cover mesal parts of the coxae ventrally, with apex of the latter process being superimposed on the former, to make mesocoxal cavities well separated in ventral view. Omophron Bonelli, 1810 has widely separated mesocoxal cavities and distinctly separated mesocoxae, which is certainly due to its nearly circular body, and the other deviations from the groundplan are only observed within Paussinae, including Ozaenini.Some of them, e.g., Pseudozaena Laporte, 1834, match well the groundplan, except only that the mesoventrite posterior to the mesothoracic peduncle is short. Many other Ozaenini demonstrate gradual reduction of the mesocoxal bridge in width and usually also in depth, as the mesocoxae become increasingly projecting and mesocoxal cavities increasingly shallow. Ventral pterothoracic structure of Eustra has most probably evolved from separating between contiguous mesocoxae (Pachyteles Perty, 1830, Dhanya Andrewes, 1919) following or, less likely, followed by totally reduced intercoxal bridge.
Neotropical Ozaenini and the remaining Ozaenini + Metriini are sister-groups based on molecular evidence [Moore, 2008], but Eustra and Dhanya were out of that analysis. While differences between Eustra and Dhanya are many, both share at least five derived character states: metatarsomere 1 as long as to much longer (vs. much shorter) than metatarsomere 5; terminal maxillary and labial palpomeres acuminate (vs. subtruncate to triangular); elytra with (vs. without) aciculate microsculpture along sides; small body size; and contiguous (vs. separated) mesocoxae/ mesocoxal cavities as primary feature. These synapomorphies combined suggest closer relationships between Eustra and Dhanya than between either and the other Paleotropical Ozaenini, and D. mulu Stork, 1985 apparently fills morphological gap between the two genera with itself. It shares more characters with Eustra than with Dhanya, i.e., clypeus bisetose on each side anteriorly, mandibles medium-sized, scape globulose, pronotal lateral edge crenulate and pilose (vs. smooth, with only 3– 4 lateral setae inside lateral edge), and meso- and metatarsal formula being similar: mesotarsi with tarsomere 1 about as long as tarsomere 5 while metatarsi with tarsomere 1 considerably longer than tarsomere 5.
Dhanya is much like a very small Itamus Schmidt-Göbel, 1846 or Sphaerostylus Chaudoir, 1848, with which it shares many characters, including more or less derived ones, such as a fairly long hexagonal clypeus, gula totally reduced behind, large mandibles, and protarsomeres 1–3 with ventro-apical angles toothed or spinose at least posteriorly (externally). Based on this evidence, Eustra may be supposed to have evolved from Dhanya, and Dhanya from ancestors close to Itamus / Sphaerostylus or something. On the other hand, the gula is posteriorly distinct in Eustra, but much reduced throughout its length in the other Ozaenini examined for comparison, ranging from nearly indistinct in width in Pseudozaena orientalis (Klug, 1831) and Sphaerostylus sp., and through reduced to a suture posteriorly (Itamus, Pachyteles (s.lato) spp., Goniotropis spp., Scythropaussus sp.) to totally reduced (Ozaena spp., Platycerozaena sp., Dhanya) — this is inconsistent with the above hypothesis. Another character of Eustra, the presense of ventral protarsal pad in male accordingly means its secondary reduction in Dhanya and Itamus, partial to complete in the former while complete in the latter.
KEY TO SPECIES OF EUSTRA OF VIETNAM
1(12) Silvicolous, macropterous and macrophthalmic species; elytra mostly bimaculate.
2(11) Body unicoloured yellow to pale brown, except for elytra each with a darker spot.
3(10) Elytral pubescence dense and long, setae as long as or barely longer than distance between neighbouring two in longitudinal row. Body slender, EL / EW 1.31–1.45.
4(5) Head, especially vertex, very convex, neck constriction very deep. Pronotal lateral edge nearly smooth. Elytral spots large, mostly extending from 2/5 to just before apex. — Southern and Central Vietnam ........................ .............................................. 3. E. posteroguttata sp.n.
5(4) Head with vertex slightly convex to nearly flat, neck constriction shallow to deep. Pronotal lateral edge nearly smooth. Elytral spots either smaller or vague.
6(7) Elytral spot median in position; ocular ridge dorsally conspicuous, entire and black. Pronotum more rectangular than in the other species and transverse, PW / PL 1.47– 1.60. BL 2.8–3.2 mm. — Southern and Central Vietnam. ..................................................... 1. E. cariniceps sp.n.
7(6) Combination of characters other than above.
8(9) Elytra vaguely infuscated on disc, without distinct spot; pronotum cordate and narrow, PW / PL 1.33. Body small, BL 2.95 mm. — Northern Vietnam ............................... ................................................ 2. E. gomyi Deuve, 2001
9(8) Elytra each with a spot extending from middle to 2/5 elytra; pronotum more transverse, PW / PL 1.50–1.57. Body larger, BL 3.5–3.7 mm. — Southern Vietnam ..... ...................................................... 4. E. dalatensis sp.n.
10(3) Elytral pubescence moderately dense and very short, setae about half as long as distance between neighbouring two in longitudinal row. Body robust, EL / EW 1.26–1.31. Elytral spots small to indistinct, between middle and 3/4 elytra. — Southern Vietnam .............. 6. E. nageli subglabra ssp.n.
11(2) Head dark brown to black, except for pale mouthparts, labrum, and clypeus; elytra dark brown, with suture, narrow lateral margin and apex, and basal third paler, reddish-brown to brown. Pronotal lateral edge tuberculate to denticulate. Elytra densely tuberculate-pubescent. .............................................. 5. E. csikii Jedlička, 1968
12(1) Cavernicolous, apterous and microphthalmic species of uniformly pale brown colour. — Kien Kiang Province. ..................................... E. honchongensis Deuve, 1996
description: Published as part of Fedorenko, D. N., 2019, New or little-known species of the genus Eustra Schmidt-Göbel, 1846 (Coleoptera: Carabidae: Ozaenini), pp. 5-16 in Russian Entomological Journal 28 (1) on pages 6-9, DOI: 10.15298/rusentj.28.1.02, http://zenodo.org/record/10919914