Brachybyrrhulus, 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 : 318-320

Brachybyrrhulus gen. n. (figs 8, 12g)

Type species: Pedilophorus discicollis Lea.

Diagnosis. The two species of Brachybyrrhulus differ from all other Byrrhinae in having 10-segmented antennae ( Figs 8 B–C). They differ from species of Akidomorychus in having curved postcoxal lines on the metaventrite ( Fig. 8 A) and normal, palpiform gonostyli and from Pseudomorychus species in having a shorter and broader body ( Figs 8 E–F) and no hind wings.

Description. Length 1.8–2.5 mm. Body very short and broad (body length/elytral width = 1.35–1.42); lateral outline more or less continuous. Colour mostly dark reddish-brown to black, but red on sides of pronotum and sometimes elytra or with entire pronotum reddish; ventral surfaces reddish-brown to black, legs reddish-brown, antennae and palps mostly yellowish-red with scape and sometimes club darker. Vestiture of dorsal surfaces consisting of long erect reddish hairs, moderately long, decumbent to suberect yellow and white hairs relatively sparsely and unevenly distributed; scutellar shield usually completely covered with white decumbent hairs; ventral surfaces with moderately long, decumbent yellow hairs.

Head about 0.85 times 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 absent. Eyes relatively small, not protuberant, located anteriorly. Frontoclypeal suture absent; frontoclypeal region strongly declined with distinct frontal ridge; antennal insertions barely concealed from above; subantennal grooves weak, not extending beyond eyes. Labrum relatively large and well sclerotized, with distinct transverse groove at base; apex subtruncate. Antennae about 0.8 times as long as head width behind eyes, 10-segmented, with 4- or 5- segmented club; scape 2.15–2.35 times as long as wide, pedicel about half as long as and slightly narrower than scape and 1.4 times as long as wide; antennomere 3 1.5–2.7 times as long as 2 and about 3.3 times as long as wide; antennomeres 4–6 at least slightly longer than wide, the last asymmetrically expanded at apex, distinctly wider than 5 but distinctly narrower than following antennomeres; 7–10 forming distinct club, the first three transverse and the terminal one 2.4 times as long as wide and broadly rounded at apex. 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. Subgenal ridges absent. Gular sutures well separated; gula transverse; corporotentorium broad, straight; cervical sclerites well-developed.

Pronotum 0.43–0.48 times as long as wide, widest at base; anterior edge broadly rounded; sides straight and gradually narrowing anteriorly; anterior angles small and narrowly acute; lateral carinae complete, narrow but visible for their entire lengths from above; posterior angles slightly acute; posterior edge broadly rounded, unmargined, with distinct posterior accessory ridge beneath; disc moderately convex. Prosternum in front of coxae about 0.5 times as long as mid length of coxal cavity, moderately convex, with paired lateral antennal grooves; anterior edge weakly concave, with concave head rest above. Prosternal process complete, slightly narrowing posteriorly and broadly rounded at apex. Procoxa more or less cylindrical, with well-developed exposed trochantin and very small coxal plate; procoxal cavities strongly transverse, broadly open externally and internally. Notosternal sutures complete and anteriorly open. Hypomeron concave posteriorly, forming with epipleuron a crural impression for housing legs and antennae.

Scutellar shield about 0.2 times as wide as base of one elytron, acute at apex. Elytra about 1.03–1.05 times as long as wide and 2.75–3.00 times as long as pronotum; sides moderately evenly rounded from base almost to apex, but slightly sinuate before apex; widest at about middle, with weak humeri; disc strongly, evenly convex; elytral apex with ventral interlocking tongue; epipeuron short, ending just beyond mesocoxa, 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, vertical procoxal rests continued onto mesanepisterna and with moderately deep mesoventral cavity; discrimen present just behind cavity. Mesoventral process short, broad and apically emarginate forming a pair of apicolateral condyles. Mesocoxae slightly transverse, with short coxal plates and exposed trochantins. Mesocoxal cavities separated by about 2 times shortest diameter of coxal cavity, partly closed laterally by mesepimera and mesanepisterna.

Metaventrite moderately long, its shortest length twice as long as shortest diameter of mesocoxal cavity; with distinct, curved postcoxal lines extending from middle of each coxal cavity to edge of metanepisternum; discrimen about 0.5 times as long as ventrite; anterior metaventral process with pair of anterolateral cavities for receiving mesoventral condyles; exposed portion of metanepisternum about 3.7 times as long as wide, widest near anterior end and gradually narrowing posteriorly; metepimeron slightly exposed. Metacoxae about 0.25 times as long as wide at base, not projecting, separated by less than 0.1 times basal width, extending laterally to meet elytra, with well-developed, complete coxal plates widest at about mesal fifth. Metendosternite moderately long, broad stalk, long, slender laminae, long, narrow lateral arms and no anterior process. Hind wings absent.

Legs relatively short; femora and tibiae subequal in length; all femora slightly impressed for reception of tibiae; protibia very slightly expanded apically and abruptly narrowed just before apex; mesotibia widest at about middle with outer edge evenly curved; metatibia slightly expanded to apical third with outer edge evenly rounded; all tibiae with short subapical groove for reception of tarsus and with outer edge bearing several spine-like setae mixed with long, fine hairs; apex with paired spurs. Tarsi 5-5-5, tarsomere 4 not or only slightly shorter than 3, tarsomere 3 without or with very short, ventral lobe; pretarsal claws simple.

Abdomen about 0.7 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, narrow, intercoxal process, narrowly rounded at apex; ventrite 5 about 1.3 times as long as 3 and 4 combined, strongly transverse and broadly rounded at apex. 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. Sternite IX in male moderately elongate, truncate at base (anteriorly) and narrowly rounded at apex (posteriorly); tergite IX transverse and undivided, broadly emarginate at apex; tergite X (proctiger) transverse, partly fused to IX, broadly rounded at apex. Aedeagus with phallobase symmetrical, slightly elongate, with subacute, dorally curved lobe at base; parameres not diverging, parallel-sided from base to apical fifth, where outer edges are abruptly narrowed to subacute apex; penis slender, slightly narrowed from base to apex, which is narrowly rounded; basal struts short. 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 about 0.6 times as long as wide at base, which is completely fused to tergite IX, broadly rounded at apex. Female proctiger 0.6–0.75 times as long as wide. Ovipositor 0.9–1.05 times as long as wide; paraprocts 0.65–0.75 times as long as gonocoxites, each of which has an elongate, lightly to moderately sclerotized, outwardly curved and cylindrical or flattened and apically narrowed distal lobe, with an apical, lightly sclerotized, palpiform gonostylus 0.1 times as long.

Etymology. Brachys (Greek, adjective), short; the Holarctic byrrhid genus Byrrhus , and ul indicating a diminutive form. The name indicates the short, broad form of included species.

Included species. B. discicollis (Lea 1920: 285) comb. n., B. malleecola sp. n.

Distribution. Apparently restricted to the mallee of western Victoria and South Australia.

Biology. Brachybyrrhulus species are among the most xerophilous of the Australian byrrhines, occurring in the mallee region of southwestern Victoria and South Australia, an arid, sandy region dominated by several dwarf eucalypt species.

Figures

FIGURE 8. Byrrhinae: Brachybyrrhulus spp.: A, B. malleecola sp. n., pterothorax, ventral, with right mesocoxa removed, showing distinct postcoxal lines on metaventrite; B, B. discicollis (Lea), antenna; C, B. malleecola sp. n., antenna; D – E, B. malleecola sp. n., habitus, length = 2.25 mm: D, lateral; E, dorsal; F, B. discicollis (Lea), habitus, dorsal, length = 2.5 mm.