Rhithrodytes sexguttatus ( AUBÉ , 1838)

Fery, Hans, 2016, Notes on Rhithrodytes BAMEUL, 1989, with the description of R. minimus nov. sp. from Algeria (Coleoptera, Dytiscidae. Hydroporini, Siettitiina), Linzer biologische Beiträge 48 (1), pp. 431-450 : 439-442

Rhithrodytes sexguttatus ( AUBÉ, 1838)

Hydroporus sexguttatus AUBÉ, 1838a: 632 + fig. 2 on plate 38, 1838b: 330; BERTOLINI 1872: 38; PORTA 1923: 251.

Hydroporus (Graptodytes) sexguttatus AUBÉ ; SEIDLITZ 1887: 61.

Graptodytes sexguttatus (AUBÉ) ; ZIMMERMANN 1919: 183, 1920: 116, 1932: 86; LUIGIONI 1929: 157; GUIGNOT 1947: 117; PORTA 1949: 101; ANGELINI 1978: 49, 1984: 71; FRANCISCOLO 1979: 401; ROCCHI 1980: 123, 1989: 86, 2001: 133; BURMEISTER et al. 1988: 177.

Rhithrodytes sexguttatus (AUBÉ) ; BAMEUL 1989: 486; NILSSON 2001: 182, 2003: 68, 2016: 159; DETTNER 2006: 98, 2007: 132; BAMEUL & QUENEY 2014: 99; NILSSON & HÁJEK 2016: 37;

Graptodytes sexguttatus ab. octoguttatus ZIMMERMANN, 1919: 183 (infrasubspecific, not available)

T y p e l o c a l i t y: Sardinia, Italy.

T y p e m a t e r i a l: S y n t y p e: ♀, "3038" [printed], " Sardaigne [hw?], Coll. Chevrolat, Det. Sharp. [18]82 [printed]", " Hydroporus 6 Guttatus Dahl, ht. [= habitat] in Sardinia Dahl" [hw Chevrolat], "Sharp det. 1882 [printed], Hydroporus sexguttatus Aubé [hw unknown]", "sec. Zimm. Cat. Junk [printed], Graptodytes sexguttatus Aubé [hw unknown]", "Coll. R. I. Sc. N. B." [printed], " Syntype, Hydroporus sexguttatus Aubé, 1838 (label mounted by H. Fery 2016)" [red, printed] (IRSN) (scans of the labels are given in Fig. 9 ). Originally, this syntype must have been pinned (hole through the right elytron and body), but someone (possibly Chevrolat) has glued the specimen onto the present card.

AUBÉ (1838a: 634) wrote that he has studied only two specimens belonging A. Chevrolat and collected by G. Dahl in Sardinia (this is why there is no doubt about the identity of the syntype mentioned above). I was not able to locate the second syntype in the collections of the IRSN or of the MNHN. Thirteen specimens are stored in the coll. Aubé of the MNHN: nine specimens on five cards, originally two specimens on each, but one specimen lost (rests of glue are recognisable) ; four glue cards with only one specimen on each card; all pins without any original label and collecting data; however, all with " Museum Paris , coll. Aubé, SEF" or "Museum Paris, SEF, coll. Ch. Aubé " ; two of the single specimens with additional " Graptodytes 6-guttatus Aubé" [hw Guignot]. According to the lack of any labels with informative data, none of these 13 specimens can be treated as syntype .

I refrain from designating the single syntype of the IRSN ( Fig. 8 ) as the lectotype because it is a female. Such nomenclatorial act (typification) would not support in any way the stability of the nomenclature, but could even be counterproductive if ever the second syntype is found and happens to be a male.

A d d i t i o n a l m a t e r i a l s t u d i e d: The ZSM houses two males which might be called "types" of Graptodytes sexguttatus ab. octoguttatus ZIMMERMANN, 1919: 183 ("type locality" Sardinia). In this aberration the basal transversal yellow band of each elytron is divided into two spots by a black longitudinal stripe, and thus both elytra together have eight yellow spots. According to article 45.6 of the ICZN (1999), this taxon has infrasubspecific rank. The labels of one of these specimens are: " Sardinien " [printed], "Type" [round light blue label, hw Zimmermann], "Samml. A. Zimmermann" [printed], "Typus" [red label, printed; unauthorised curatorial designation], male gender symbol, " Graptodytes sexguttatus ab. octoguttatus Zimmerm. [type-written], " Rhithrodytes sexguttatus (Aubé) [hw Bameul], F. Bameul det. 1988 [printed]". The second specimen has the same labels, except that the type-written label is lacking and the text of the red label is " Paratypus " (see Figs 10 and 11 for habitus and labels).

Additionally, I have studied a large amount of specimens from diverse localities in Corsica and Sardinia, mainly collected by myself. Especially specimens from Corsica vary considerably not only in body shape and elytral pattern, but also in the shape of the median lobe of aedeagus. At present I cannot judge whether this is due to intraspecific variation or whether different species/subspecies are involved. More well-founded statements may become possible when still further material and, in particular, molecular data of specimens from diverse localities will become available.

N o t e s: Since its description R. sexguttatus was dealt with in numerous publications (only a small part of which are listed above) and cited from Sardinia, Corsica, Elba, Isle of Montechristo and continental Italy (especially from Tuscany). However, there has been confusion about the identity of this species until BAMEUL (1989) published his revision of this species group and created the new genus Rhithrodytes . In particular, the distribution of the species is – in my opinion – not clear. Sardinia and Corsica as well as Elba seem to be correct, but I regard "Tuscany" a doubtful record. The source of this eventual misunderstanding may be BERTOLINI (1872: 38) who gave "Cors., Sard." for R. sexguttattus and "Cors., It. sup. [= upper Italia]" for Rhithrodytes crux (FABRICIUS, 1792) . SEIDLITZ (1887: 61) gave " Italien, Sardinien, Corsica " for R. sexguttatus , but on the same page for R. crux "Toscana" and " Corsica ". SAINTE- CLAIRE DEVILLE (1914: 53) gave for R. sexguttatus central Italy, Corsica and Sardinia, but doubted SEIDLITZ' record of R. crux from Corsica. PORTA (1923: 251) reported R. sexguttatus from Sardinia, Corsica and " Italia centrale". LUIGIONI (1929: 157) reported R. sexguttatus among others from Tuscany ("App. tosc." = Tuscany Apennines); same did PORTA (1949: 101; " Toscana "). These records were repeated by FRANCISCOLO (1979: 401), ROCCHI (1989: 86, 2001: 133), and DETTNER (2006: 98). ANGELINI (1984: 71) referred to FRANCISCOLO' s records and added "Fornovolasco" (in Tuscany, 44.03N 10.36E, ca. 25 km NNW Lucca). To my knowledge, this is the only record for continental Italy with more detailed data on the collecting site. ANGELINI' s record was repeated by BAMEUL (1989: 488) and by DETTNER (2006: 98). As far as I know, no further collecting of this species was ever made in Tuscany or other localities on continental Italy.

I strongly doubt all records from Tuscany, in particular, because at the time of the publication of ANGELINI’ s and FRANCISCOLO’ s works the identity of R. sexguttatus was disputed and in part the species was set in synonymy with R. bimaculatus (cf. the discussion on p. 402 of FRANCISCOLO 1979; see also GUIGNOT 1947: 118). Additionally, I have collected recently (25.6.2016) in brooks near Fornovolasco and found 36 specimens of Rhithrodytes , most of them at a locality (ca. 44.026N 10.358E) which is only 250 m apart from the centre of that village. All specimens turned out to be R. crux (FABRICIUS, 1792) and not a single R. sexguttatus was found.

Figures

Figs 8-9: Female syntype of Hydroporus sexguttatus AUBÉ, 1838: (8) habitus; (9) labels (scale bar 2 mm).

Figs 10-11: "Type" of Graptodytes sexguttatus ab. octoguttatus ZIMMERMANN, 1919: (10) habitus; (11) labels (scale bar 2 mm).