Dineura stilata ( Klug, 1816 )

Liston, Andrew, Prous, Marko & Vårdal, Hege, 2019, The West Palaearctic Dineura species, focussing on Sweden (Hymenoptera, Tenthredinidae), Zootaxa 4612 (4), pp. 501-517 : 505-509

Dineura stilata ( Klug, 1816)

Tenthredo (Allantus) stilata Klug, 1816: 82–83 . Syntypes ♀, “in hiesiger Gegend” [= Berlin area]; lectotype ♀ here designated, in ZMHUB (GBIF-GISHym2756, images: https://doi.org/10.6084/m9.figshare.7851272).

Type locality: Berlin ( Germany). Paralectotypes: 2 ♀ (GBIF-GISHym 2757 and 2758), same data as the lectotype, in ZMHUB .

Nematus apicalis Stephens, 1835: 32 . Syntypes, sex not stated, Coomb Wood near London, possibly in BMNH, not examined. Synonymy with stilata by Cameron (1885).

Selandria scapularis Stephens, 1835: 46 . Syntypes, sex not stated, near London, possibly in BMNH, not examined. Synonymy with stilata by Konow (1905).

Nematus xanthocerus Hartig, 1840: 23 . Syntypes, sex not stated, “Nordeutschland” [according to introductory text]; lectotype ♀ here designated, in ZSM (GBIF-GISHym3099, images: https://doi.org/10.6084/m9.figshare.7851299). Type locality: northern Germany. Paralectotypes: 1♀ (GBIF-GISHym3098), 1♂ (GBIF-GISHym3100), same data as the lectotype, in ZSM. Synonymy with stilata by Dalla Torre (1894).

Nematus posticus Förster, 1854: 349–350 . Syntypes ♂, near Aachen; lectotype ♂ here designated, in ZSM (GBIF-GISHym3091, images: https://doi.org/10.6084/m9.figshare.7851314). Type locality: Aachen. Paralectotypes: 5♂ (GBIF-GISHym3092 to 3096), same data as the lectotype, but undated, in ZSM. Synonymy with Nematus xanthocerus by Wüstnei (1885).

Nematus xanthopus Zaddach, 1876 : Plate III, Fig. 5. Syntypes larvae [subsequent description of adult by Brischke (1883): 167–168]; Danzig, Schottland, Elberfeld, München, Hamburg, Halle, Kopenhagen, Harz; lectotype ♀ here designated, in ZMHUB (GBIF-GISHym2760, images: https://doi.org/10.6084/m9.figshare.7851338). Type locality: Copenhagen. Synonymy with Nematus xanthocerus by Wüstnei (1885).

Dineura melanoxantha Zaddach, in Brischke, 1883: 232–233 . Syntypes ♀ ♂, Rostock, material lost. Listed in synonymy with stilata by Blank & Taeger (1998).

Dineura sulcifrons Konow, 1885: 296–297 . Syntypes ♀ ♂, “Corvin an der Persante” [now in Poland: West Pommerania, Powiats Białogardzki and Świdwiński], type material lost. Synonymy with stilata by Konow (1905).

Dineura sulcata: Konow (1890) , misspelling of sulcifrons .

Dineura nigro-flava Magretti, 1886: 24–25 . Holotype ♂ (SDEI-GISHym956, images: https://doi.org/10.6084/ m9.figshare.7856762), Senago ( Italy), in MSNG. Synonymy with stilata by Konow (1905).

Dineura stilata var. virilis Enslin, 1918: 732 . Syntypes ♀, type locality not stated; lectotype ♀ here designated, in ZSM (GBIF- GISHym3097, images: https://doi.org/10.6084/m9.figshare.7851413). Type locality: Denmark.

Nematus v-flavum Cameron, 1882: 537. Syntypes ♀, type locality not stated, possibly in BMNH, not examined. Tentative syn- onymy with stilata by Morice (1906).

Taxonomy. Enslin (1915) treated stilata and testaceipes as separate species, which he distinguished using colour characters. The range of variability which he described for each taxon fits quite closely with our observations. Since then there has been some controversy about the status of stilata and testaceipes . Conde (1938) may have been the first specialist to treat them as conspecific, but he did not explain why he did so. Lindqvist (1955) examined the genitalia of specimens which he held to represent stilata and testaceipes , and found no significant differences. He concluded from this observation, and because he thought that the larvae are “sehr gleichartig” [very similar], that “ testaceipes kaum für eine eigene, jedenfalls keine gute Art, sondern nur für eine Farbenform von stilata gehalten werden kann” [ testaceipes can hardly be held to be a distinct, and in any case not for a good species, but only as a colour form of stilata ]. However, it later transpired that what he identified as stilata were pale individuals of testaceipes : Dineura stilata is not at present known in Finland. Benson (1958) treated them as separate species, separated only by the colour pattern of the abdomen. Pschorn-Walcher & Altenhofer (2006) discussed the taxonomic problem in the light of observations on larvae: [translated from German] “ Dineura testaceipes (Klug) [.] Larvae collected end IX/03 from rowan ( Sorbus aucuparia ) near Schrems in the Waldviertel. Imagines emerged in the following year from end V to start VI. The species is said (as for D. stilata (Klug)) to occur also on hawthorn ( Crataegus ) ( Taeger et al. 1998). The separation of the two species using variable colour characters seems unreliable, particularly as the saws and male genitalia can hardly be distinguished ( Lindqvist 1955). Foodplant-choice tests with D. stilata ( Martens 1989) indicate rather the existence of hostplant races ( D. testaceipes on Sorbus , D. stilata on Crataegus ) or the effects of conditioning (preference for the host plant on which the larvae developed). Further rearing would be desirable”. The study by Macek (2015) presents a rather different conclusion: stilata and testaceipes are separate species, clearly distinguished by larval morphology, with testaceipes using both Sorbus and Crataegus as hosts, but stilata only on Crataegus . Here, we follow Macek’s (2015) opinion, which is supported by small but constant differences between the penis valves of stilata and testaceipes . Nevertheless, the taxonomy of these taxa would benefit from further study, preferably including additional sequence data for nuclear genes.

Additional description. Body length: ♀ 5.0– 6.3mm, ♂ 4.9–5.7. Head black, labrum and clypeus more or less pale. Scape and pedicel black (Fig. 7); flagellum dorsally dark and ventrally pale, or completely pale in some males. Pterostigma pale, with margins more or less darkened. Female (Figs 12–13): meso- and metanotum completely black, or mesoscutal lobes more or less pale-bordered. Upper mesepisternum extensively pale. Abdomen completely pale, apart from mostly black tergum 1, and sometimes smaller black markings on terga 2–3. Male (Fig. 14): meso- and metanotum completely black. Mesepisternum usually completely black, rarely pale above. At least abdominal tergum 1 largely black, often with some black markings medially on following terga, but one or more middle terga always completely pale. Penis valve: ventral spine slightly longer than dorsal one; dorsal spine basally wide relative to length ( Figs 30–31 ). The penis valve is thus more similar to that of parcivalvis ( Figs 34–35 ) than testaceipes ( Figs 32–33 ).

Total number of specimens examined: 35.

Similar species. Only very pale specimens of testaceipes (Fig. 15), found in warmer parts of central and southern Europe, but not in Fennoscandia, are likely to be confused with stilata (Fig. 12). However, the palest female testaceipes specimens have parts of the mesoscutum pale-marked, whereas the mesoscutum of stilata is always

Distribution. Widely distributed through most of Europe, including the British Isles, but not recorded in the

Iberian Peninsula ( Taeger et al. 2006). Not definitely known from outside Europe: according to Zhelochovtsev &

Sweden: Öland : 1♂ (NHRS-HEVA000003428) [no further data], leg. Boheman ( NHRS). 2♂ (DEI-GIS- Hym 31796), Station Linné 1km E, 40 m, 56.62°N 16.51°E, 29.05.2013 , Liston , Prous & Taeger ( SDEI). 1♂, same data as previous, but 30.05.2013 . 1♂, same data as previous, but leg. Liston, 17.06.2016 . 1♂, Mörbylånga kommun, Gamla Skogsby (Kalkstad), “diversitetsängen”, 56.62°N 16.51°E, 20.05.– 28.06.2006, leg. SMTP ( NHRS). 1♂, same data as previous, but 01– 16.06.2005 .

Figures

FIGURES 28–35. Dineura, penis valves. 28 virididorsata ♂, penis valve (80155). 29 virididorsata ♂, penis valve (19664; formerly det. pullior). 30–31 stilata ♂, penis valve (11350). 32–33 Dineura testaceipes ♂, penis valve (31800). 34 Dineura parcivalvis ♂, Russian Far East, penis valve (80232). 35 Dineura parcivalvis ♂, Finland, penis valve [“allotyp” FMNH].