Idiothrix, Lawrence, John F., Slipinski, Adam, Jäger, Olaf & Pütz, Andreas, 2013

Lawrence, John F., Slipinski, Adam, Jäger, Olaf & Pütz, Andreas, 2013, The Australian Byrrhinae (Coleoptera: Byrrhidae) with descriptions of new genera and species, Zootaxa 3745 (3), pp. 301-329 : 311-315

Idiothrix gen. n. ( Figs. 6 , 11 B)

Type species: Pedilophorus carinaticeps Lea 1920 .

Diagnosis. The single species included in this genus is distinguished by the partial fusion of the metaventrite and metanepisternum ( Fig. 6 E), the complex vestiture with dark erect bristles mixed with recumbent yellow, organge and black thickened setae ( Figs 6 A–B), and the presence of paired glandular openings on abdominal ventrites 4 and 5 ( Fig. 6 D). The inflated posterior pronotal angles and large crural impression involving the hypomera and elytral epipleura are somewhat similar to those in Nothochaetes , but in addition to the features mentioned above, I. carinaticeps differs in having a 4-segmented antennal club ( Fig. 6 C) and tibiae lined with fine setae only and not stout spine-like setae.

Description. Length 2.3–3.0 mm. Body oblong (body length/greatest width = 1.45–1.53), moderately strongly convex; lateral outlines more or less continuous, but somewhat sinuate; dorsal outline continuous with highest point at about middle of elytra. Upper surfaces more or less even, except for elytral bases, each of which bears a well developed humeral callus and two short, weak, longitudinal elevations between this and the scutellar shield; head and pronotum smooth and shiny, but elytral surface appearing rough due to granulose interspaces. Colour of head, pronotum and scutellum dark reddish-brown to black; elytra primarily metallic green, somewhat darker along sides and suture and on small patches on disc; undersurfaces and legs reddish-brown; antennae and palps yellow. Dorsal vestiture complex, consisting of moderately long, decumbent, thickened, yellow and orange setae over most of surface, decumbent black setae on scutellum and in small patches on elytra and scattered, long, erect, black bristles on pronotum and elytra. Ventral surfaces clothed with short, fine, yellow decumbent hairs.

Head almost as long as width behind eyes, strongly declined and deeply inserted into prothorax, but with eyes at least partly visible; occipital region with short median endocarina; transverse occipital ridge weakly developed. Eyes relatively small, not protuberant, located anteriorly. Frontoclypeal suture absent; frontoclypeal region weakly declined without distinct frontal ridge; antennal insertions barely concealed from above; subantennal grooves weak, extending to edges of eyes. Labrum relatively large and well sclerotized, with distinct transverse groove at base; apex subtruncate. Antennae slightly longer than head width behind eyes, 11-segmented, with 4-segmented club; scape about twice as long as wide; pedicel about half as long as and slightly narrower than scape and 1.5 times as long as wide; antennomere 3 about 1.5 times as long as 2 and 5 times as long as wide; antennomeres 4–6 slightly longer than wide and 7 about as long as wide and more or less globular; first three club segments distinctly transverse and the last about 1.2 times as long as wide. Mandible broad, subtriangular and obliquely tridentate; dorsal surface with distinct ridge fitting against sides of labrum; mesal surface of mandibular base without mola but with basal brush of hairs. Maxilla with short, densely setose galea and lacinia; apical maxillary and labial palpomeres more or less fusiform, those of the labium shorter and broader. Subgenal ridges present but weakly developed. Gular sutures well separated; gula transverse; corporotentorium broad, straight; cervical sclerites welldeveloped.

Pronotum about 0.46–0.54 times as long as wide, widest at base; anterior edge broadly rounded but with weak emargination at middle; sides inflated and slghtly raised at base, gradually narrowing and sinuate anteriorly; anterior angles well developed and acute; lateral carinae complete but narrow and weakly defined, not visible for their entire lengths from above; posterior angles right; posterior edge somewhat angulate, unmargined, with distinct posterior accessory ridge beneath; disc moderately convex, slightly impressed anterolaterally. Prosternum in front of coxae relatively short, about 0.5 times as long as mid length of coxal cavity, slightly convex, with paired lateral antennal grooves and a concave head rest above. Prosternal process complete, parallel-sided and subtruncate at apex. Procoxa more or less cylindrical, with well-developed exposed trochantin and short coxal plate produced to form tooth-like process; procoxal cavities strongly transverse, broadly open externally and internally. Notosternal sutures complete and anteriorly open. Hypomeron concave posteriorly, forming with epipleuron a large impression for housing legs and antennae.

Scutellar shield about 0.2 times as wide as base of one elytron, about as long as wide and acute at apex. Elytra about 1.03–1.05 times as long as wide and 2.2–2.5 times as long as pronotum; sides sharply sinuate anteriorly, widest at middle and narrowing posteriorly, with distinct, somewhat inflated and angulate humeri; disc moderately convex, base with pair larger, ovate humeral calli at lateral third and a smaller pair of elongate tubercles at mesal third; elytral apex without ventral interlocking tongue; epipleuron short, ending just beyond mesocoxa, relatively wide and deeply concave, forming posterior part of crural impression. Mesoventrite strongly transverse, separated by complete sutures from mesanepisterna, which are very widely separated; anterior edge on different plane than metaventrite, with a pair of large, strongly declined procoxal rests continued onto mesanepisterna and with moderately deep mesoventral cavity; discrimen not apparent. Mesoventral process short, broad and apically emarginate forming a pair of apicolateral condyles. Mesocoxae slightly transverse, with short coxal plates and with exposed trochantins. Mesocoxal cavities separated by about 1.36 times shortest diameter of coxal cavity, partly closed laterally by mesepimera and mesanepisterna, which are more or less fused together.

Metaventrite moderately short, its shortest length subequal to shortest diameter of mesocoxal cavity; without distinct postcoxal lines but with weak, angulate crural impressions; discrimen about 0.15 times as long as ventrite; anterior metaventral process with pair of anterolateral cavities for receiving mesoventral condyles; metanepisternum exposed, but partly fused to metaventrite, the suture visible only at anterior end. Metacoxae about 0.33 times as long as wide at base, not projecting, separated by about 0.1 times basal width, extending laterally to meet elytra, with well-developed, complete coxal plates, each bearing a rounded projection at about middle. Metendosternite with moderately long, broad stalk, long, narrow lateral arms and no laminae or anterior process. Hind wings absent.

Legs relatively short; femora and tibiae subequal in length; all femora grooved for reception of tibiae; protibia distinctly wider at apical third, with distinct tarsal impression extending almost to base; meso- and metatibiae slightly wider at middle, without or with weak tarsal impression, outer edges of all tibiae lined with fine setae. Tarsi 5-5-5, tarsomere 4 reduced, tarsomere 3 bearing a long, hyaline, setose ventral process longer than body of tarsomere; pretarsal claws simple.

Abdomen about 0.85 times as long as wide at base with five ventrites, the first three of which are connate; first ventrite with anterolateral corners slightly impressed and with short, subacute intercoxal process; ventrite 5 about as long as 3 and 4 combined, broadly rounded at apex; ventrites 4 and 5 each with pair of lateral glandular openings. Abdominal tergites lightly sclerotized or membranous. Functional spiracles on abdominal segments I– VIII. Anterior edge of sternite VIII in male with short, broad, truncate anterior projection, posterior edge slightly concave. Sternite IX in male slightly elongate, subtruncate at base (anteriorly) and broadly rounded at apex (posteriorly); tergite IX transverse and undivided, broadly emarginate at apex; tergite X (proctiger) free from tergite IX, about as long as wide at base, broadly rounded at apex. Aedeagus with phallobase symmetrical, about 1.6 times as long as wide, narrowed anteriorly with broadly rounded lobe at base; parameres not diverging, broadest at base, gradually narrowed and subacute at apex; penis more or less parallel-sided, slightly narrowed apically, narrowly rounded and cleft at apex. Female proctiger about as twice as long as wide at base, broadly rounded at apex. Anterior edge of sternite VIII in female biemarginate or with short angulate or truncate anterior process (spiculum ventrale), posterior edge broadly rounded; tergite VIII transverse and undivided; tergite IX consisting of paired laterotergites (paraprocts) connected at midline by a slender, lightly sclerotised strip. Female proctiger slightly longer than wide. Ovipositor about 2.25 times as long as wide; paraprocts about 0.85 times as long as gonocoxites, each of which has well sclerotized, slightly compressed distal lobe slightly curved dorsolaterally, strongly curved at apex, with a well sclerotized, cylindrical gonostylus 0.14 times as long.

Etymology. Idios (Greek, adjective), distinct, individual and thrix, trichos (Greek, f), hair. Name implies the unusual nature of the vestiture.

Included species: I. carinaticeps (Lea 1920: 284) comb. n..

Distribution: Known only from Tasmania.

Figures

FIGURE 6. Byrrhinae: Idiothrix carinaticeps (Lea): A – B, habitus, length = 2.7 mm: A, lateral; B, dorsal; C, antenna; D, abdomen, ventral, showing glandular pores on ventrites 4 and 5; E, pterothorax, ventral, with right coxa removed, showing partial fusion of metanepisternum and metaventrite.

FIGURE 11. Byrrhidae, scanning electron micrographs: A, Akidomorychus raucus (Blackburn), protorax and fore legs, anterior; B, Idiothrix carinaticeps (Lea), anterior portion of head, anterodorsolateral, with right mandible removed, showing left mandibular ridge and groove fitting onto side of labrum; C – D, Nothochaetes howensis sp. n.: C, prothorax, ventral, with both coxae removed; D, left hypomeron, showing oblique ridge and anterior impression. E, Microchaetes sp.: prothorqax, ventral, with right coxa and leg removed, showing characteristic triangular sternal plate. F, Nothochaetes fasciculatus (Lea), right hypomeron, showing curved ridge and deep anterior fossa.