Exochomoscirtes Pic, 1916

Ruta, Rafał & Yoshitomi, Hiroyuki, 2010, Revision of the genus Exochomoscirtes Pic (Coleoptera: Scirtidae: Scirtinae) 2598, Zootaxa 2598 (1), pp. 1-80 : 6-13

Genus Exochomoscirtes Pic, 1916

Exochomoscirtes Pic, 1916: 6

Type species: Exochomoscirtes binotatus Pic, 1916 (present designation).

Diagnosis. Metafemora enlarged; metacoxae meeting along full length of median line; body hemispherical to elongate oval, moderately to very convex. Elytral epipleura wide, inner edge of basal portion of epipleura trough-shaped. Palpomeres of maxillary palpi distinctly widened in females, narrower in males, apical palpomere axe-shaped; mandibles short, without denticles on inner edges. Penis small, consisting of oval or elongated pala and narrow, filiform parameroids. Tegmen peculiar, with three projections. Parameres long and narrow, widened or hooked apically. Females without excitators (sensu Ruta 2008), apical ventrite with paired fovea of glandular character. Prehensor elongated, tubular, often in accordion-folded membranous theca. Bursal sclerite well developed.

Redescription. Adult. Body oval, length 1.1–1.3(1.5) X width, moderately to strongly convex, elytra uniformly yellowish-brown to blackish-brown, or with contrasting pattern consisting of large red, orange or yellow spots. Dorsum with evident punctation, covered with semierect setae. Head very wide, 1.8–2.1 X its length, concealed from above by pronotum, with distinct punctation; eyes large, oval, protuberant, finely facetted; almost reaching subgenal ridge (genae almost entirely reduced); distance from posterior margin of eye to occipital ridge slightly smaller than half the eye length; tempora very short; sides of head behind eyes slightly converging basally; transverse occipital carina subtly marked, continued ventrally as subgenal ridges; paired supraantennal carinae not elevated, joined mesally to clypeal margin, frons flat; paired antennal fossae lying below carinae and extending laterally to edge of eye and ventrally reaching lower margin of eye; antennal insertions small and partly visible from above (situated near antennal carinae). Fronoclypeal suture absent; clypeus transverse, moderately short, lateral margins diverging anteriorly. Anteclypeus absent. Ventral portion of head behind occipital carina and between subgenal ridges slightly convex, gular area strongly convex, impunctate; submentum short, strongly transverse. Antennae filiform to subtly serrate; antennomere 1 widest, cylindrical, with a subtle trace of anterior ridge in anterior portion, antennomere 2 globular, shortest, antennomere 3 narrowest and as long as antennomere 2, antennomeres 4–11 of similar length to antennomeres 2 and 3 combined.

Labrum transverse, arising from the basal portion of clypeus, distinctly narrower than clypeus, 2/3 of its length concealed below clypeus, ca. 1/3 visible, anterior margin subtly emarginated or truncate, anterior angles widely rounded. Mandibles ( Fig. 1C ) ca. 1.5 X longer than wide, subtriangular, with unidentate apices; molar region well marked, covered with weak setae. Prostheca absent, inner margin of mandibles with sharp ridge, denticles absent, mandibles with sparse setae on outer margin. Maxillae ( Fig. 1B , 2 ) with narrow galea, not widening apically and covered with numerous long setae, arranged into two fan-shaped rows; anterior margin of lacinia covered with long, strong setae, without apical uncus, setae in basal half are less regularly and sparser arranged than setae in apical half; additional row of setae parallel to interior margin absent; palpomeres of maxillary palpi strongly widened in females, apical palpomere arising from cup-shaped preapical one, truncate at apex. Palpomeres of maxillary palpi in males less widened, apical palpomere axe-shaped. Mentum ( Fig. 1A ) transversely semioval with rounded lateral margins contiguous with anterior margin; ligula relatively narrow, widened apically, not emarginated at apex; apical labial palpomere arising from the side of widened, obliquely truncate preapical palpomere.

Pronotum strongly transverse, trapezoidal, over 2 X wider than long, widest at posterior angles; lateral margins straight, distinctly converging anteriorly, anterior margin straight, not extending beyond anterior angles, covering base of the head; anterior angles triangularly explanate; posterior angles acute to rightangled; base subtrapezoidal, with subtle margination (often reduced in mesal portion), basal foveae absent; disc of pronotum slightly convex. Prosternum highly reduced anteriorly, consisting of a pair of narrow areas of cuticle extending in front of coxal cavities; prosternal process laminar and narrow, apical portion only slightly widened, apex rounded, keel-shaped, covered with very small setae. Anterior coxa triangularly cylindrical, with smooth field delimited by subparallel carinae, forming area fitting protibiae. Anterior coxal cavities widely opened.

Scutellum equilaterally triangular, flat, with straight margins, apex pointed. Elytra oval to elongate oval, lateral margins often explanate, angle between pronotum and elytra not marked in dorsal outline; humeri well visible, apices regularly rounded, extended into triangular projections, elytra usually without traces of longitudinal ridges, adsutural stria not marked; elytral surface smooth; epipleura wide at bases, slightly wider than metanepipleuron, regularly narrowing behind metanepipleuron till elytral apex, not reduced in apical portion; epipleura in basal 1/3 with trough-like depression; elytral punctation confused, not granulate (moderately dense, distance between punctures ca. 1.0 puncture).

Mesoventrite ( Figs. 1D–E ) very short; lateral margins strongly oblique; anterior margin with subtle traces of coxal rests; mesoventral discrimen present in apical portion of intercoxal process, anterior portion forming distinct narrow, deep fossa for reception of prosternal process; mesoventral process narrow (but not laminate) and moderately long (L/W ca. 2.0) with subparallel sides, bilobed in posterior 1/3, touching metaventrite; mesocoxa completely separated by mesoventral process; mesanepisternum relatively wide, rhomboidal, forming depression for reception of anterior coxa, smooth, shining, impunctate; mesepimeron much smaller, strongly narrowed mesally, impunctate and shining; mesocoxal cavities closed laterally by narrow processes of mesanepisternum and mesepimeron; mesocoxa elongated, transversely oval (L/W ca. 2.0), slightly projecting; mesotrochantin moderately well developed and exposed, partly hidden, somewhat elongated.

Metaventrite ( Figs. 1D–E ) relatively short, moderately convex; metaventral discrimen present in posterior 3/4; metanepisternum subrectangular, ca. 1.7 X longer than its width (wider in anterior portion); anterior margin forming elevated ridge (followed by subtle depression). Metacoxa moderately large, ca. 2.8 X longer than its width, reaching epipleura; metacoxal plate well developed in mesal 1/4, absent in lateral portion. Metacoxal plates touching one another mesally. Metendosternite wide, ventral processes absent.

Wings (description based on E. maculatus , Figs. 1F–G ) ca. 2.0 X longer than its width; radial cell triangular, as long as wide; apical portion of r3 short, well sclerotized, straight; r4 slightly visible; rp-mp2 forming almost right angle with MP 1+2. Medial field with three free veins, MP 4 long, situated in the middle of the length of CuA + AA 1+2; several pigmented areas located as follows: radial cell and radial field around radial cell, three patches in apical field; patches between MP 1+2 and MP 3 and between MP 1+2 and RA. Radial bar may be abruptly curved in the vicinity of radial cell.

Legs relatively short and wide; hind coxae meeting along full length of median line; trochanters moderately long, posterior trochanters with small denticle on distal end; trochanterofemoral joint oblique; femora distinctly (ca. 20%) longer than tibia, femora widened in the middle of its length, protibiae and mesotibiae narrow and not widened apically; lateral portion of tibiae with distinct paired carinae; tibial spurs well developed, spurs on anterior and mesotibiae of similar length, distinctly shorter than width of tibiae; metatibial spurs well developed, dorsal one at least as long as tarsomere 1, ventral one a bit longer than half length of dorsal one. In males of several species dorsal spur is modified: with flattened lobe, elongated and hooked, widened or tridentate at apex. Posterior femora strongly widened, ca. 4–5 X wider than greatest width of metatibiae; distance between lateral carinae of metatibiae greater than in anterior and mesotibiae; length of tarsi greater than half length of tibiae, tarsomere 1 in protibiae and mesotibiae as long as tarsomeres 2–3 combined, claws simple. Posterior tarsi modified, tarsomere 1 longer than remaining, tarsomeres 2–4 of similar length, apical tarsomere almost as long as tarsomeres 3 and 4 combined.

Abdomen wider than its length (its width 1.4 X length in E. binotatus ), flattened; ventrites 1–4 of similar length, ventrite 5 a bit longer, ventrite 1 usually with a trace of keel in the basal 1/3; ventrite 5 subtly emarginated at apex. Laterosternites well developed, narrow, present on ventrites 1–4. Tergites 1–7 moderately sclerotized, regularly covered with setae, on sides of anterior margins of tergites 1–6 small oval areas devoided of setae are present, which are anteriorly contiguous with membranous portion; tergite 7 in males of several species modified (projecting or divided into lobes, Fig. 5 ).

Terminal segments and male genitalia. Sternite 8 small, widely U-shaped or transversely rectangular, often indistinct, sternite 9 consisting of two hemisternites, which are basally fused in some species, strongly sclerotized apically, with tuft of setae on apex, tergite 8 narrow, moderately to strongly elongated, sometimes with narrow emargination at apex, with a row of setae on margin. Tergite 9 moderately elongated, sometimes with emarginated apex and row of setae on apical margin.

Aedeagus dorsoventrally flattened; penis reduced, small, pala triangular, oval, elongate oval or pearshaped, in apical portion subtle filiform processes (parameroids) and elongated mesal process are present; tegmen with transverse basal portion, parameres large, long, apically dilated or hooked, between parameres a long median process with rounded apex is present, usually somewhat shorter than parameres.

Female genitalia. Sternite 8 consisting of a pair of triangular sclerites; tergite 8 with long apodemes, apical margin with a row of setae; ovipositor very long, longer than abdomen, its length ca. 8 X greatest width, branchlets small, but present, coxites membranous, elongated, with erect setae, styli with two tufts of setae. Prehensor tubular, usually long and narrow, strongly sclerotized, surrounded by accordion-folded membranous theca continuing as a duct connecting with bursa copulatrix; bursal sclerite small, symmetrical, consisting of two flat, oblong sclerites.

Sexual dimorphism. Metatibial spurs in males of several species ( E. dilaticornis , E. discoidalis , E. longispinus , E. nigromarginatus , E. picturatus ) are modified ( Fig. 3 ): elongated, enlarged, armed with denticles. Tergite 7 ( Fig. 5 ) can bear projections in males of several species ( E. jaechi , E. klausnitzeri , E. luteosuturalis , E. quadripartitus , E. ruforotundus ); ventrite often with paired foveae. Palpomeres of maxillary palpi broadened in females. Sexual dichroism can be observed in E. discoidalis and E. ceylonicus .

Larva (based on E. klausnitzeri sp. nov., identified by comparison with a larval exuvia of reared adult). Body ( Figs. 7–8A) about 10.0 mm in fully expanded specimen. Coloration of body almost brown, but legs and ventral surface of body paler.

Head transverse, bearing short setae on lateral margins; two non-melanized stemmata situated on each side of head. Antennae long, reaching about abdominal segment 2; scape short, slightly curved posteriorly; pedicel straight, longer than scape; flagellum long, about 120 segmented. Labrum ( Fig. 8F ) a little longer than wide, ventral lobes distinctly protruding, covered with short setae on dorsal surface, bearing long hairy setae in anterior portion. Epipharynx ( Fig. 8G ) with a pair of stout and pectinate long setae and four pairs of stout short setae at apices of ventral lobes, with a pair of stout short setae in anterointernal part of ventral lobes, closely covered with short hairy setae on interior parts of ventral lobes; anterior margin clearly projecting anteriorly in mesal part; surrounding parts of sockets of ventral setae elevated. Mandibles ( Fig. 8D ) with simple terminal teeth, bearing normal bristles in interior parts. Maxillary palpi ( Fig. 8B–C ) long and slender, 4-segmented; segment 1 long, bearing long setae on lateral parts; segment 2 punctulate in ventral surface, with a pair of long setae in dorsal surface; segment 3 with three pairs of ovate sensory organs on interior part of ventral surface; segment 4 short, with sensory organs at apices; approximate ratio of each segment (1–4) as 4.4: 2.6: 3.0: 1.0. Hypopharynx ( Fig. 8E ) a little longer than wide; keel-sclerite contiguous with socket of tooth-bristles, with six sensilla situated on base of stout and pectinate setae; tooth-bristles wide, bicornate at ends; comb teeth composed of 10–14 short projections; cushion area closed, with small membranous cushion. Thorax widest at mesonotum, bearing long setae on lateral margins. Legs relatively short; tibiotarsal organ ( Fig. 8H ; sensu Zwick, 2008) in fore legs present, consisting of some spinous short setae situated in apicoventral portion; tarsungule with two short setae and minute spines.

Abdomen gently tapered posteriorly, bearing closely short setae in lateral portion. Tergite 8 ( Fig. 8I ) trapezoidal, bearing long spinous setae in lateral portion, slightly bicornute at middle of anterior margin; sternite 8 ( Fig. 8K ) transversal semicircular, bearing long setae at lateral margins; tergite 9 ( Fig. 8J ) arch-shaped, with pectinate setae along anteroventral margin, apical part projecting posteriorly, with a pair of long setae in posterolateral corners; sternite 9 ( Fig. 8L ) semicircular, bearing pectinate setae on posterior margin.

Biology. The only published data on the biology concern E. ruforotundus , which was collected in a tree hollow and from bamboo internodes ( Watts 2004). At Mahua waterfall, Sabah, Borneo, larvae of E. takizawai sp. nov. were collected by H. Yoshitomi from a small phytotelmata (ca. 30 x 3 cm, depth ca. 7 cm) in buttress root, an adult female was collected on the same root ( Fig. 9 ). E. klausnitzeri sp. nov. and E. discoidalis (Pic) were collected together in the bamboo phytotelmata by Ch. Watts (see below).

Distribution. SE Asia (Java, Sumatra, Borneo, Sulawesi, continental SE Asia), a single species is known from New Guinea and northern Australia.

Figures

FIGURE 1. Morphological details of Exochomoscirtes. A) Exochomoscirtes rufomaculatus Pic, labium; B) Exochomoscirtes rufomaculatus Pic, maxilla; C) Exochomoscirtes rufomaculatus Pic, mandible; D) Exochomoscirtes picturatus sp. nov., meso- and metaventrite; E) Exochomoscirtes picturatus sp. nov., meso- and metaventrite, closeup; F) Exochomoscirtes maculatus (Waterhouse), wing; G) Exochomoscirtes dilaticornis sp. nov., wing.

FIGURE 2. Exochomoscirtes picturatus sp. nov., maxilla. A) male; B) female.

FIGURE 3. Metatibial spurs in Exochomoscirtes. A) E. dilaticornis sp. nov.; B) E. discoidalis (Pic); C) E. longispinus sp. nov.; D) E. nigromarginatus sp. nov.; E) E. picturatus sp. nov.; F) E. takizawai sp. nov.

FIGURE 5. Abdominal details in Exochomoscirtes. A) E. dilaticornis sp. nov., ventrite 5; B) E. discoidalis (Pic), ventrite 5; C) E. jaechi sp. nov., tergite 7; D) E. klausnitzeri sp. nov., tergite 7; E) E. luteosuturalis sp. nov., tergite 7; F) E. luteosuturaloides sp. nov., tergite 7; G) E. maculatus (Waterhouse), abdomen; H) E. maculatus (Waterhouse), ventrites 3–5; I) E. nigromarginatus sp. nov., ventrite 5; J) E. quadripartitus sp. nov., tergite 7.; K) E. ruforotundus (Watts) (Australia), tergite 7; L) E. takizawai sp. nov., ventrite 5.

FIGURE 8. Exochomoscirtes klausnitzeri sp. nov., details of larval morphology. A) habitus; B) maxillary palpus, dorsal view; C) maxillary palpus, lateral view; D) mandible; E) hypopharynx; F) labrum; G) epipharynx; H) foreleg; I) tergite 8; J) tergite 9; K) sternite 8; L) sternite 9. Scale bars = 0.5 mm.

FIGURE 9. Exochomoscirtes takizawai sp. nov., habitat. A) Mahua waterfall, Sabah, Borneo; B) phytotelmata in buttress root inhabited by larvae; C) adult female on the root (H. Yoshitomi phot.).