Scydmaenus (Parallomicrus) inflatitibia Franz

Jałoszyński, Paweł, 2023, Scydmaenus Latreille of Australia: Revision of species in subgenera Choleropsis Franz, Kingius Franz, Mascarensia Franz, Parallomicrus Franz, Scottiscydmaenus Franz, and description of Ascydmaenus subgen. n. (Coleoptera, Staphylinidae, Scydmaeninae), Zootaxa 5371 (1), pp. 1-75 : 47-50

publication ID	https://doi.org/ 10.11646/zootaxa.5371.1.1
publication LSID	lsid:zoobank.org:pub:D60B50D1-280B-4403-9E5B-25C0704A43A1
DOI	https://doi.org/10.5281/zenodo.10249305
persistent identifier	https://treatment.plazi.org/id/3E380C57-FFDB-4A72-27AC-B3DAFA43E7ED
treatment provided by	Plazi
scientific name	Scydmaenus (Parallomicrus) inflatitibia Franz
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Treatment

Scydmaenus (Parallomicrus) inflatitibia Franz View in CoL

Scydmaenus (Allomicrus) inflatitibia Franz, 1975: 284 View in CoL .

( Figs 118–124 View FIGURES 118–124 , 199 View FIGURES 189–205 )

Type material studied. Holotype ( AUSTRALIA: NEW SOUTH WALES): ♂ ( Fig. 120 View FIGURES 118–124 ), with labels illustrated in Fig. 199 View FIGURES 189–205 : “ N.S.Wales, ‘ Botany Bay / 1901. 42” [white with pink line below middle, handwritten], “ Heterognathus / A.M.Lea det.” [white, handwritten and printed], “ Scydmaenus / ( Heterognathus ) / inflatitibia / det. H.Franz m.” [white, handwritten and printed], “Typus” [red, handwritten], “Holo- / type” [white circle with red margin, printed] ( BNHM) . Paratype: ♀, “ N.S.Wales, ‘ Botany Bay / 1901. 42” [white with pink line below middle, handwritten], “Para- / type” [white circle with yellow margin] {unlabelled by Franz but listed in original description; identity uncertain, see Remarks} ( BNHM) .

Additional material studied. NEW SOUTH WALES: ♂, Acacia Plateau, J. Armstrong ( ANIC).

Revised diagnosis. In male antennomeres 3–4 each about 1.5 × as long as broad, 5 twice as long as broad, 6 1.5 × as long as broad, antennomeres 9 and 10 each 1.4 × as long as broad, and antennomere 11 less than twice as long as broad, with triangularly expanded angulate outer lateral margin ( Fig. 120 View FIGURES 118–124 , right antenna); metatibiae strongly modified ( Figs 118–120 View FIGURES 118–124 ), each medially broadened and with lateral (outer) elongate deep concavity surrounded by sharp margins and filled with setae, apical region constricted, narrowed and curved; pronotum with two pairs of antebasal pits; aedeagus in dorsal view ( Figs 121, 123 View FIGURES 118–124 ) with broad apex of median lobe, slightly narrower than half of widest (subapical) site of median lobe, flanked by weakly elongate, subtriangular weakly sclerotized lateral subapical lobes; median lobe lacking setae.

Redescription. Body in male ( Fig. 120 View FIGURES 118–124 ) slightly flattened, elongate and relatively slender, BL 1.75–1.81 mm; pigmentation uniformly light brown (including appendages); cuticle moderately glossy, covered with vestiture of setae slightly lighter than body.

Head (Fi. 120) in dorsal view indistinctly transverse and somewhat subhexagonal, broadest at eyes, HL 0.30– 0.34 mm, HW 0.33–0.35 mm; vertex and frons confluent and weakly convex, posterior margin of vertex evenly arcuate and anteriorly convex; tempora about 2.5 × as long as length of eye in dorsal view; supraantennal tubercles indistinct; frons over antennal fossae broadly subtriangular and with rounded anterior margin. Eyes small, weakly oval, not emarginate posteriorly and oblique in relation to long axis of head. Punctures on frons and vertex fine, inconspicuous; setae (including those on tempora) short, sparse, nearly recumbent. Genae as sparsely setose as frons and vertex. Anterior (exposed) region of head capsule demarcated from neck region by short abrupt impression around occipital constriction, anterior margin of gular plate on neck region with indistinct, narrow anteriorly-directed projection. Antennae ( Fig. 120 View FIGURES 118–124 ) long and slender, AnL 1.00– 1.03 mm; three terminal antennomeres forming indistinctly delimited club; scape 2.5 × as long as broad, distinctly broadening distally; pedicel 1.8 × as long as broad; antennomeres 3–4 each about 1.5 × as long as broad, 5 twice as long as broad, 6 1.5 × as long as broad, 7 and 8 each distinctly asymmetrical and each about as long as broad, 9 1.4 × as long as broad and barrel-shaped, 10 1.4 × as long as broad and distinctly broadening distally, 11 much shorter than 9 and 10 combined, about 1.6 × as long as broad, distinctly asymmetrical, with broadly subtriangular, angulate expansion on proximal region of outer margin (visible in right antenna in Fig. 120 View FIGURES 118–124 ).

Pronotum in dorsal view ( Fig. 120 View FIGURES 118–124 ) distinctly elongate, broadest between middle and anterior third, PL 0.50 mm, PW 0.40–0.41 mm; anterior margin arcuate and laterally confluent with rounded lateral margins, so that anterior corners are not marked; posterior corners obtuse-angled and blunt; posterior margin nearly straight at middle and bent anteriorly at sides; base with very narrow and indistinct posterior marginal carina, with two pairs of distinct, small and slightly transverse pits. Pronotal disc covered with fine, shallow and unremarkable sparse punctures; setae similar to those on head, moderately dense and long, suberect. Ventrally prothorax with nearly asetose and impunctate hypomera and basisternal region only slightly longer than procoxal rests, sparsely covered with moderately long recumbent setae.

Elytra ( Figs 109 View FIGURES 109–110 , 113 View FIGURES 113–117 ) oval, broadest slightly in front of middle, EL 0.95–0.98 mm, EW 0.65–0.68 mm, EI 1.41–1.50. Humeral calli small but distinctly elevated and each mesally demarcated by shallow and transverse basal elytral impression; basal elytral foveae lacking; apices separately rounded. Elytral punctures fine and inconspicuous; setae similar to those on pronotum, moderately dense. Hind wings fully developed.

Legs ( Fig. 120 View FIGURES 118–124 ) long and slender. Metatibia ( Figs 118–120 View FIGURES 118–124 ) strongly modified, medially broadened, with strongly elongate oval cavity on lateral (outer) surface demarcated by sharp edges and filled with setae, distal 1/4 rapidly narrowed, almost constricted and distinctly curved. Protarsi with tenent setae on tarsomeres 1–3, protarsomere 1 moderately strongly broadened, weakly elongate, 2–4 each almost as long as broad, 5 about 2.5 × as long as broad; mesotarsi longer than protarsi, mesotarsomere 1 about 3 × as long as broad, tarsomeres 2–4 each weakly elongate, tarsomere 5 about 2.5 × as long as broad; metatarsi slightly longer than mesotarsi, metatarsomere 1 about 3 × as long as broad, tarsomeres 2–4 each distinctly elongate, but decreasing in length distally, tarsomere 5 about 3 × as long as broad.

Aedeagus ( Figs 121–122 View FIGURES 118–124 ) elongate but not very slender, AeL 0.38 mm, in dorsal view median lobe (excluding lateral subapical lobes) broadest in distal 1/3, narrowing both distally and proximally, but basal region again broadened, apex slightly less than half as wide as total width of median lobe, apical margin indistinctly concave; lateral subapical lobes large, each subtriangular and slightly longer than wide, projecting laterally; flagellum broadened in proximal region to form asymmetrical coils; median lobe lacking setae; ostium situated in distal third of median lobe, far from its apex.

Female. Unknown (see Remarks).

Distribution. SE Australia: CE and NE New South Wales.

Remarks. The identity of the only known paratype female is uncertain. This specimen is remarkably smaller than the holotype male (BL 1.60 mm vs. 1.75), and it may belong to a different species.

Scydmaenus inflatitibia combines some characters typical of Parallomicrus (fused metanepisterna), Choleropsis (two pairs of antebasal pronotal pits), and Corbulifer (modified metatibia in males). It remarkably differs from S. myrmecobius , especially in aedeagal features. Although the aedeagus within the large genus Scydmaenus is poorly studied, its general structure is usually stable within subgenera. For instance, it was demonstrated that despite a wide spectrum of metatibial modifications in Corbulifer , the structure of the aedeagus is very similar in all species, i.e., all of them, independently of the shape of the median lobe, share long setae and asymmetrical proximal ‘chambers’ of the flagellum ( Jałoszyński 2018). All species of Choleropsis treated in the present study also have asymmetrical proximal flagellar coils, whereas two known species of Kingius , four Australian species of Scottiscydmaenus , and two species of the newly described Ascydmaenus subgen. n. share not coils, but symmetrical expansions of the proximal flagellar region, which appear as three consecutive ‘chambers’ demarcated by constrictions. Scydmaenus (Mascarensia) australiensis has strongly asymmetrical, broad coils, and even though the previously studied Scydmaenus (Mascarensia) kasuganus Franz, 1976 has a clearly different shape of the median lobe, its proximal flagellar region is also strongly asymmetrical in the dorsal view ( Jałoszyński 2022). Two species of Scydmaenus belonging in the subgenus Geoscydmaenus and inhabiting Madagascar have symmetrical proximal flagellar regions ( Jałoszyński 2016b). These observations suggest that groups of closely related species have similar structures of the flagellum. However, in the Australian Parallomicrus , S. myrmecobius has symmetrical ‘chambers’, whereas in S. inflatitibia they form a loose spiral. Because external features (pronotal pits, male secondary sexual modifications) are also different in these two species, in future they may be placed in separate subgenera.

Subgenus Scottiscydmaenus Franz

Scottiscydmaenus Franz, 1975: 277 View in CoL (as subgenus of Scydmaenus View in CoL ). Type species: Scydmaenus lodoiceae Scott, 1922 View in CoL (des. orig.).

Diagnosis. Franz (1975) defined Scottiscydmaenus by the following characters: (1) antennae with slender trimerous clubs with elongate antennomeres 9 ( Fig. 127 View FIGURES 127–129 ); (2) the pronotum strongly convex, lacking antebasal pits and a longitudinal carina ( Fig. 125 View FIGURES 125–126 ); (3) elytra strongly convex, lacking humeral calli and humeral folds ( Fig. 130 View FIGURES 130–134 ); (4) metanepisterna not demarcated from the metaventrite ( Fig. 128 View FIGURES 127–129 ); (5) the profemur in males with two ventral carinae, anterior one distally with a broad and blunt projection ( Fig. 129 View FIGURES 127–129 ); and (6) protibia in males distally weakly broadened, laterally flattened. The latter character was here found rather problematic, as the protibiae in all studied species are almost unmodified ( Fig. 129 View FIGURES 127–129 ).

Remarks. The status of Scottiscydmaenus as a separate subgenus will require verification. The Australian species share similarly modified profemora in males (with a distal anterior/dorsal tooth ( Fig. 129 View FIGURES 127–129 )—the anterior/dorsal terminology refers to the femur observed in the position as in Fig. 130 View FIGURES 130–134 ); antennae with conspicuously slender proximal flagellomeres and also a slender, elongate antennomere 9, so that the club appears as dimerous ( Fig. 127 View FIGURES 127–129 ); barely broadened protarsi in males with only sparse, poorly visible tenent setae ( Fig. 129 View FIGURES 127–129 ); pronota lacking pits ( Fig. 125 View FIGURES 125–126 ); elytra with reduced humeral structures (humeral calli, humeral folds, and basal impressions) due to lack of wings ( Fig. 125 View FIGURES 125–126 ); lack of lateral submental lobes ( Fig. 126 View FIGURES 125–126 ); the basisternal region of the prosternum distinctly, but not much longer than procoxal rests ( Fig. 126 View FIGURES 125–126 ); a narrow, almost carinate mesoventral intermesocoxal process ( Fig. 128 View FIGURES 127–129 ); metaventral intermetacoxal process about as wide as one metacoxa ( Fig. 128 View FIGURES 127–129 ); and the aedeagus in dorsal view narrowing distally, in lateral view weakly curved, lacking lateral subapical lobes, with dorsodistal minute setae and symmetrical ‘chambers’ of the proximal flagellar region (e.g., Figs 136–139 View FIGURES 135–144 ). However, it is unclear if this set of characters is sufficient to define a separate subgenus.

Composition, distribution and biology. Scottiscydmaenus includes six valid species names, but two of them were found to be synonymous during the present study, and one more new species is described. This subgenus is distributed in Madagascar, Seychelles (Praslin), and continental Australia. The Australian species are relatively variable in the body length and proportions of body parts; the most stable features are the shape of the head and the profemoral tooth in males. Scydmaenus clarkianus Franz , S. brachyponerophilus sp. n. and S. swanensis have been collected from colonies of the ant Brachyponera lutea (Mayr) ; S. optatus Sharp from colonies of B. lutea and Rythidoponera victoriae (André) . It is possible that the relatively large variation in body size and proportions of body parts found among the Australian Scottiscydmaenus is due to a partial or complete genetic isolation of local populations living in fragmented habitats.

Identification key to males of Australian species of Scydmaenus (Scottiscydmaenus) View in CoL

1 Head (together with mouthparts) clearly elongate........................................................... 2

- Head about as long as broad............................................................................ 3

2 Profemoral tooth sharp-angled and elongate; BL> 2 mm ..................... .. Scydmaenus brachyponerophilus sp. n.

- Profemoral tooth at most right-angled, broader than long or as long as broad; BL <2 mm ... Scydmaenus clarkianus Franz View in CoL

3 Length of temple in dorsal view equal to about 3 × length of eye; body slender; aedeagus in dorsal view with subapical broadening as wide as sub-basal broadening................................................. Scydmaenus optatus Sharp View in CoL

- Length of temple in dorsal view equal to about 2 × length of eye; body robust; aedeagus in dorsal view with subapical broadening narrower than sub-basal narrowing............................................ Scydmaenus swanensis Franz View in CoL