Rhyzobius serratus, Czerwiński & Szawaryn & Tomaszewska, 2020

Czerwiński, Tomasz, Szawaryn, Karol & Tomaszewska, Wioletta, 2020, Three new species of the genus Rhyzobius Stephens, 1829 from New Guinea (Coleoptera: Coccinellidae: Coccidulini), European Journal of Taxonomy 692, pp. 1-17 : 11-15

Rhyzobius serratus sp. nov.

urn:lsid:zoobank.org:act:96A5BE00-3CB9-4A99-AEDE-73284A171644

Figs 1 I–L, 3C, E, G, I, 4G–I, 5J–M

Diagnosis

This species is similar to R. amabilis Weise, 1918 and R. papuensis Tomaszewska, 2010 , but it can be distinguished from them by having elytra with a distinct, oval area along the mid length of the elytral suture covered with only small punctures surrounded by rows of coarse macropunctures (similar to R. weiri Tomaszewska, 2010 ), and the prosternal process with carinae joined before the anterior prosternal margin and continuing anteriorly as a single carina. This shape of prosternal carinae is similar to that in R. atramentarius sp. nov., but R. serratus sp. nov. differs from it by lacking of tibial spurs, the eyes without interfacetal setae, ventrite 5 in the male with the posterior margin emarginate and by having distinct metaepimeron.

Etymology

The name of this species derives from the Latin and refers to the serrate outer surface of the penis guide.

Material examined

Holotype

NEW GUINEA • ♂; Madang Province , Mt Wilhelm, Bananumbo; 5º45ʹ33.4ʺ S, 145º14ʹ08.2ʺ E; 1700 m a.s.l.; 30 Oct.–1 Nov. 2012; “06727-CoCocc Ibisca Niugini 2012”; FIT-MW1700-S-3/8-d06; plot 19, order 10233; MNHN.

Type locality

Papua New Guinea, Madang Province, Mt Wilhelm, Bananumbo.

Description

MEASUREMENTS. Length 2.30 mm; TL/EW = 1.21; PL/PW = 0.45; EL/EW = 1.0.

BODY ( Fig. 1 I–K). Broadly oval, strongly convex dorsally, hemispherical, winged; black and shiny; antennae, mouthparts, tarsi and abdominal ventrites (except ventrite 1) pale brown. Dorsum with double pubescence consisting of appressed setae and sparse darker stiff bristles distinct along elytral lateral margins only; dorsal pubescence not forming pattern on elytra.

HEAD ( Fig. 1L ). Withdrawn into prothorax with eyes partially visible externally; ventral antennal grooves distinctly circularly bent towards outer margin of eye. Eyes dorsally with inner orbits convergent, closer near vertex than anteriorly; ocular canthus extending slightly into eye; interocular distance 0.53 times as wide as head across eyes; interfacetal setae indistinct. Antenna composed of 11 antennomeres, about 0.75 times as long as head capsule width; scape large, swollen, 1.55 times as long as pedicel; pedicel barrel-shaped, narrower than scape, 1.3 times as long as wide; antennomere 3- 2.30 times as long as wide, and about 2.5 times as long as 4; antennomere 4- 1.15 times as long as 5; antennomeres 5 and 6 quadrate, antennomere 7 obconical, at base about 0.75 times as wide as at apex and about 1.2 times as long as antennomere 6. Antennal club consisting of 3 antennomeres, with two subterminal segments asymmetrical; antennomere 9 as long as antennomere 10 and distinctly shorter than terminal antennomere; terminal antennomere distinctly elongate, rounded apically. Anterior clypeal margin distinctly emarginate, with rounded lateral lobes and with median area membranous. Labrum truncate at apex. Maxilla with cardo transverse with outer angle reaching slightly outside of mouth cavity ( Fig. 3G ); terminal palpomere 1.1 times as long as wide, weakly expanded apically. Mentum transverse, about 1.5 times as wide as long; anterior margin almost straight; ventral surface with horseshoe-like impression; prementum as long as broad; ligula parallel-sided; labial palps separated by distance about equal to width of palpiger; apical palpomere as long and as broad as penultimate one; submentum distinct.

PRONOTUM. With anterolateral angles rounded, not swollen, but with distinct groove near angles; anterior and hind margin without border; lateral margin with entire border. Prothoracic hypomeron ( Fig. 3I ) with broad, concave area along anterior half of prothoracic lateral margin; notosternal suture distinct, simple; prosternal process 0.6 times as broad as longest coxal diameter, its surface with carinae joined before apex and continuing anteriorly as single carina; prosternum in front of coxa about 0.65 times as long as coxal longitudinal diameter at the same position; anterior margin continuing as weakly arcuate line, much more posterior than anterior pronotal margin; procoxal cavity distinctly transverse, without visible bordering line.

PTEROTHORAX. Anterior margin of mesoventrite ( Fig. 3I ) with complete raised border; mesoventral process at median length of coxa about 1.20 times as broad as corresponding coxal diameter; mesometaventrite articulation with suture visible; junction angulate posteriorly. Scutellar shield transverse, triangular, surface punctate and setose. Elytra with lateral margins narrow, but entirely visible from above; surface with distinct, oval area with small punctures along mid length of elytral suture surrounded by rows of coarse macropunctures ( Fig. 3E ). Elytral epipleuron incomplete apically, 2.5 times as wide as corresponding metaepisternum, inner margin with border area narrow throughout and border line fading before base of elytron. Metaventrite coarsely punctate, with complete discrimen; metaventral postcoxal lines distinctly separated at middle, recurved and complete laterally; metaepisternum with external process interlocking with fovea on elytron; metaepimeron distinct, visible ventrally.

LEGS. With trochanters angulately produced ( Fig. 3C, I ); tibiae without visible apical spurs; fore and mid tarsal claws in male appendiculate, holotype specimen misses metatibiae and tarsi.

ABDOMEN ( Fig. 4G ). With five ventrites; ventrite 1- 1.6 times as long as ventrite 2; abdominal postcoxal lines separate medially, recurved and complete anteriorly, deep, posteriorly nearly reaching anterior margin of ventrite 2; ventrite 5 simply setose, hind margin narrowly emarginate; hind margin of sternite VIII weakly emarginate ( Fig. 4H ), tergite VIII rounded.

MALE TERMINALIA AND GENITALIA ( Figs 4I , 5 J–M). Male genital segment with sternite IX with central part membranous ( Fig. 4I ); apodeme of male sternum IX rod-like, and base of spiculum widened, membranous. Penis base with outer arm obsolete, inner arm well developed; penis apex as in Fig. 5 J–K. Parameres ( Fig. 5 L–M) articulated with phallobase, well developed, simple and separated, comparatively narrow, about 0.9 times as long as penis guide, with apices covered with simple setae; penis guide broad, without additional processes with outer margin serrate along apical half, widest at about apical sixth, with lateral sides sinuate but symmetrical throughout, with upturned apex; tegminal strut simple.

Female. Not known.

Distribution

Papua New Guinea: Mt Wilhelm.

An updated key to species of Rhyzobius from New Guinea (based on Tomaszewska, 2010)

1. Dorsum uniformly blackish or deeply black .................................................................................... 2

– Dorsum bicoloured (black and brown, orange or yellowish) ........................................................... 7

2. Elytra with strongly intensive, three-coloured (green, violet and blue) metallic sheen ..................... ....................................................................................................... R. metallicus Tomaszewska, 2010

– Elytra with moderately intensive, unicoloured metallic sheen or without metallic sheen ............... 3

3. Mid and hind tibia with single apical spur ........................................................................................ 4

– Mid and hind tibia without apical spurs ........................................................................................... 5

4. Body large (2.85–3.65 mm long); elytra coarsely punctate; prosternal carinae subparallel, joined roundly before anterior prosternal margin ...................................... R. iracildae Tomaszewska, 2010

– Body smaller (2.00– 2.35 mm long); elytra less coarsely punctate; prosternal carinae joined before anterior prosternal margin and continuing anteriorly as a single carina .... R. atramentarius sp. nov.

5. Body large and oval; prosternal carinae complete and separate .................. R. amabilis Weise, 1918

– Body mostly smaller and more elongate; prosternal carinae joined anteriorly ................................ 6

6. Pronotum distinctly swollen towards anterolateral angles; prosternal carinae complete, joined anteriorly in form of triangle; prothoracic hypomeron with short crescent shaped groove perpendicular to notosternal suture ...................................................................... R. papuensis Tomaszewska, 2010

– Pronotum not swollen towards anterolateral angles; prosternal carinae joined before anterior margin of prosternum and continuing anteriorly as a single carina, forming bell-like shape; prothoracic hypomeron with broad concave area along anterior half of prothoracic lateral margin .................................................................................................................. R. serratus sp. nov.

7. Elytra black with small, preapical, yellowish, round oval spot on each elytron; pronotum black ..... .................................................................................................... R. bipunctatus Tomaszewska, 2010

– Elytra black without spots, or with brown apex; pronotum brown or bicoloured (black and brown) ........................................................................................................................................................... 8

8. Ventral antennal grooves reaching beyond posterior margin of eyes, straight; pronotum with regular border ................................................................................................................................................ 9

– Ventral antennal grooves distinctly circularly bent towards outer margin of eye; pronotum usually with at least weak groove near anterior angles ............................................................................... 10

9. Prosternal process smooth, not carinate; elytra black with yellow apices .......................................... ................................................................................................................. R. jaya Tomaszewska, 2010

– Prosternal carinae joined roundly before prosternal margin and continuing anteriorly as single carina; elytra entirely black ................................................................. R. leucochaetus Tomaszewska, 2010

10. Pronotum black or dark brown with at least lateral margins light brown ........................................11

– Pronotum brown, sometimes weakly infuscate at base .................................................................. 12

11. Pronotal lateral margins distinctly swollen towards anterolateral angles of pronotum and with deep groove near angles; prosternal process with carinae joined before anterior margin of prosternum and continuing anteriorly as single carina ............................................... R. poorani Tomaszewska, 2010

– Pronotal lateral margins not swollen, without groove near anterolateral angles of pronotum; prosternal process with complete carinae, joined anteriorly in form of triangle ................................ ............................................................................................................................... R. albinos sp. nov.

12. Mid and hind tibia with single apical spur; prosternal carinae joined roundly before anterior margin of prosternum and continuing anteriorly as single carina .............. R. gonzalezi Tomaszewska, 2010

– Mid and hind tibia without apical spurs; prosternal carinae separate throughout their length or joined but not continuing anteriorly as single carina ................................................................................. 13

13. Body stronger convex in dorsal aspect; elytra mostly black with violet metallic sheen, apex somewhat paler; prosternal carinae complete and separated; male ventrite 5 with admedian setose patches, apical margin narrowly truncate .................................................... R. violaceus Tomaszewska, 2010

– Body less convex; elytra entirely black with cupreous metallic sheen; prosternal carinae joined roundly just before prosternal margin; male ventrite 5 simply setose and with apical margin rounded ............................................................................................... R. luciae Tomaszewska, 2010

Figures

Fig. 1. Habitus of new species of Rhyzobius spp. (holotypes). A–D. R. albinos sp. nov., ♂ (MNHN). E–H. R. atramentarius sp. nov., ♂ (MNHN). I–L. R. serratus sp. nov., ♂ (MNHN). A, E, I. Dorsal view. B, F, J. Ventral view. C, G, K. Lateral view. D, H, L. Frontal view. Scale bars = 0.5 mm.

Fig. 3. SEM images of Rhyzobius spp. (holotypes). A–B, D, F, H. R. atramentarius sp. nov., ♂ (MNHN). C, E, G, I. Rhyzobius serratus sp. nov., ♂ (MNHN). A. Habitus, dorsal. B–C. Habitus, ventral. D. Pronotum. E. Details of elytral punctation. F–G. Head, ventral. H–I. Pro-, meso- and metathorax, ventral. Scale bars: A–C = 1.0 mm; D–E, H– I = 0.5 mm; F = 0.4 mm; G = 0.3 mm.

Fig. 4. Abdomens and male terminalia of Rhyzobius spp. A–C. R. albinos sp. nov. D–F. R. atramentarius sp. nov. G–I. R. serratus sp. nov. A, D, G. Abdomen. B, E, H. Abdominal segment VIII, ventral. C, F, I. Male genital segment, dorsal. Scale bars: A, D, G = 0.5 mm; B–C, E–F, H–I = 0.2 mm.

Fig. 5. Male and female genitalia of Rhyzobius spp. A–D. R. albinos sp. nov. E–I. R. atramentarius sp. nov. J–M. R. serratus sp. nov. A, E, J. Penis, lateral. B, F, K. Apex of penis. C, G, L. Tegmen, inner view. D, H, M. Tegmen, lateral. I. Female genitalia. Scale bars: 0.2 mm.