Dactylosternum Wollaston 1854
Creators: name: Mai, Zuqi
name: Hu, Jian
name: Minoshima, Yûsuke N.
name: Jia, Fenglong
name: Fikáček, Martin
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Hydrophilidae
Dactylosternum

description: Dactylosternum Wollaston, 1854
(Figs. 1–71)
Dactylosternum Wollaston, 1854: 99. Type species: Dactylosternum roussetii Wollaston
For complete synonymy, see Hansen (1999).
Diagnosis. Body oblong oval to broadly oval, moderately to strongly convex, more or less uniformly brown to black; antenna with 9 antennomeres in Asian species, antennal bases concealed by lateral parts of clypeus, club (antennomeres 7–9) loosely segmented or compact; labrum completely concealed by clypeus or partially exposed in front of clypeus in Chinese and Japanese species; frontoclypeal suture distinct; maxillary palps with 4 palpomeres, stout; labial palps with 3 palpomeres, rather stout; gula forming a transverse triangle posteriorly, narrow and parallelsided anteriorly; prosternum more or less tectiform medially, often with a distinct tooth anteromedially; hypomeron pubescent except on marginal portion, without defined antennal grooves; metaventrite with pubescence except on raised median portion; metaventral process strongly projecting anteriorly between mesocoxae, abutting mesoventral elevation; elytron with at least 9 rows of serial punctures or striae, the outer serial punctures usually larger and deeper than the inner serial punctures; sides of elytron more or less explanate at least in posterior half; elytral epipleuron wide and reaching elytron end; first abdominal ventrite with complete or almost complete carina medially.
Biology. All species of Dactylosternum for which biology is known are terrestrial. They usually occur in various types of decaying plant material, including that under bark of freshly cut trees (Bloom 2014) and in tropical forest leaf litter (Fikáček 2010, Fikáček et al. 2020). In tropical areas, Dactylosternum abdominale (Fabricius, 1792) was found in banana trees (Figs. 65, 67) and its larvae are predators of the banana weevil (Koppenhöfer 1995); in temperate areas the same species is found in domestic waste or farmyard manure (Lõkkös 2009). Dactylosternum cacti (LeConte, 1855) in inhabiting rotting cactus tissues (Archangelsky 1994, Arriaga-Varela et al. 2019). Many Chinese species were collected in the decaying pseudostem of banana plants and in rotten wood (Figs. 67–69). Dactylosternum nanlingensis Mai et Jia, sp. nov. was collected from fungal hyphae on fallen wood (Figs. 64, 66), and D. songxiaobini Mai et Jia, sp. nov. was collected from a rotten wood with termites.
A list of Chinese Dactylosternum Wollaston, 1854
Dactylosternum abdominale (Fabricius, 1792)
Dactylosternum corbetti Balfour-Browne, 1942
Dactylosternum frater Mai et Jia, sp. nov.
Dactylosternum hydrophiloides (MacLeay, 1825)
Dactylosternum latum (Sharp, 1873)
Dactylosternum nanlingensis Mai et Jia, sp. nov.
Dactylosternum pseudolatum Mai et Jia, sp. nov.
Dactylosternum pui Jia, 2002
Dactylosternum salvazai Orchymont, 1925
Dactylosternum songxiaobini Mai et Jia, sp. nov.
A list of Japanese Dactylosternum Wollaston, 1854
Dactylosternum abdominale (Fabricius, 1792)
? Dactylosternum latum (Sharp, 1873) (doubtful)
A key to species of Dactylosternum in China and Japan
1 Antennal club loosely segmented (Fig. 39). Body broadly oval, strongly convex................................... 2
- Antennal club compact (Fig. 40). Body elongate to oval, anterior half of elytra nearly parallel-sided, weakly to moderately convex.............................................................................................. 4
2(1) Anterior margin of clypeus pubescent; elytral series 1–3 reaching basal half of elytra; punctures on pronotum simple, without lateral scars (Fig. 43); ventral surface of mesofemora fully covered with dense pubescence except on extreme apex (Fig. 41); body reddish brown to piceous brown (Fig. 4). China .................................................. D. pui Jia
- Anterior margin of clypeus not pubescent; all elytral series nearly reaching elytral base; punctures of pronotum with lateral scars (Figs. 44–45); ventral surface of mesofemora only covered with pubescence along anterior margin (Fig. 42); body dark brown to black....................................................................................... 3
3(2) Body size less than 4 mm; elytral sutural stria distinct in posterior half; with nearly 20 serial punctures. China. … D. songxiaobini ......................................................................... Mai et Jia, sp. nov.
- Body size more than 4 mm; elytral sutural stria almost reaching basal third elytra; with 10 serial punctures. China ................................................................................ D. nanlingensis Mai et Jia, sp. nov.
4(1) Body size less than 5 mm; pronotum with distinct microsculpture on interstices or arising from the punctures, at least on the lateral portion (Figs. 46–47)............................................................................. 5
- Body size more than 5 mm; pronotum without any trace of microsculpture on interstices............................. 6
5(4) Body size less 4 mm; moderately convex; each puncture on vertex, pronotum, scutellum and elytron connected with two diverging impressed short lines (Fig. 46). China ....................................... D. corbetti Balfour-Browne
- Body size over 4 mm; weakly convex; clypeus, posterior margin of vertex and lateral portion of pronotum with distinct meshlike microsculpture on interstices, the lines are not connected to punctures (Fig. 47). China and Japan ................................................................................................. D. abdominale (Fabricius)
6(7) Body weakly convex; anterior margin of clypeus with distinct marginal rim (Fig. 18); interstices of elytral intervals with dense micropunctures, especially in posterior half (Fig. 51); median lobe very short and broad, apex rounded, reaching only to the midlength of parameres; parameres almost as long as phallobase (Fig. 24). China ........... D. hydrophiloides (MacLeay)
- Body moderately convex; anterior margin of clypeus without marginal rim (Fig. 19); elytral interval punctures with associated microsculpture especially in posterior half, but intersticed smooth (Figs. 52–55); median lobe a little shorter than parameres, pointed at apex; parameres distinctly longer than phallobase................................................... 7
7(6) Posterior margin of abdominal ventrite 5 with a distinct marginal rim and a stria (Figs. 60–61)........................ 8
- Posterior margin of abdominal ventrite 5 with very fine marginal rim or without it, without stria (Figs. 62–63)........... 9
8(7) Anteromedial portion of metaventrite behind metaventral process with a Λ-shaped divergent ridges (Fig. 57); each elytral ground puncture attached with a K/H-shape microsculpture especially in the posterior half (Fig. 53); posteromedial portion of abdominal ventrite 5 with mesh-like microsculpture (Fig. 61); outer margin of parameres not sinuate, not so curved as in D. pseudolatum (Figs. 25a, 25b); ventral plate of the median lobe rounded apically (Fig. 25c). China ... D. salvazai Orchymont
- Anteromedial portion of metaventral process with a short transverse groove (Fig. 56); each elytral ground puncture attached with one/two transverse lines especially in posterior half (Fig. 52); posteromedial portion of abdominal ventrite 5 with fine punctures (Fig. 60); parameres distinctly sinuate on outer margin and more curved subapically (Figs. 27–29); ventral plate of the median lobe strongly pointed apically (Figs. 27c, 28c). China ................... D. pseudolatum Mai et Jia, sp. nov.
9(7) Anteromedial portion of metaventral process with a strongly impressed pit (Fig. 58); median lobe widest at basal third or at midlength, outer margin nearly parallel-sided medially, gonopore situated subapically (Figs. 30–38). China and possibly Japan .................................................................................. D. latum (Sharp)
- Anteromedial portion of metaventral process slightly depressed (Fig. 59); median lobe widest at basal third, gradually narrowing towards apex, outer margin not parallel-sided, gonopore situated apically (Fig. 26). China ...... D. frater Mai et Jia, sp. nov.
description: Published as part of Mai, Zuqi, Hu, Jian, Minoshima, Yûsuke N., Jia, Fenglong & Fikáček, Martin, 2022, Review of Dactylosternum Wollaston, 1854 from China and Japan (Coleoptera, Hydrophilidae, Sphaeridiinae), pp. 269-300 in Zootaxa 5091 (2) on pages 271-272, DOI: 10.11646/zootaxa.5091.2.3, http://zenodo.org/record/5843837