Rhogogaster magniserrula Viitasaari

Taeger, Andreas & Viitasaari, Matti, 2015, European Rhogogaster s. str., with notes on several Asian species (Hymenoptera: Tenthredinidae), Zootaxa 4013 (3), pp. 369-398 : 376-377

Rhogogaster magniserrula Viitasaari , spec. nov.

( Figs 4n–p , 5e, f , n, 6p, 7a–q)

Material examined. Holotype ♀ (high resolution figures see http://dx.doi.org/10.6084/m9.figshare.1324048). Finland: “ Suomi PP: Simo 12.6.1948, O. Peltonen” (ca. 65.670°N, 25.052°E), coll. SDEI.

Paratypes: Finland: 1 ♀ Sipoo, Nevas, 6687:3412, margin of deciduous forest, (ca. 60.285°N, 25.408°E) 14– 20.7 .1985, A. Albrecht leg., coll. MV; 1 ♀ EnL, Enontekiö, Pallastunturit, Röyninkuru, (Grid2E) 756:337, 26.7.1951, J. Kaisila leg. (ca. 68.074°N, 24.058°E), coll. MV. This specimen was found on snow and the record was published as “ R. viridis L.”, identified by T. Kontuniemi [ Kaisila 1952: 19]. This paper gives a fairly accurate location between Saivokero and Vuontiskero (http://dx.doi.org/10.6084/m9.figshare.1411048). Russia: 1 ♀ “Kirov: Kirov: Vyatka 15–23 July 2001. Sweep-net. Leg. Erik Heibo” (ca. 58.462°N, 49.877°E), coll. E. Heibo (http:// dx.doi.org/10.6084/m9.figshare.1375774).

Description. The species is described in the key below.

Variability. The holotype and the paratype from Sipoo are very similar to each other, whereas the specimen from Enontekiö is somewhat paler, but all three are clearly darker than the paratype from Russia. The saw of the latter specimen is strongly worn ( Fig. 5f ). Nevertheless, there is little doubt that these four specimens are conspecific. The specimen from Russia has a much paler abdomen: all terga apically largely green, and the black patches only cover about half of the length of the terga ( Fig. 7 n). In contrast, the Finnish specimens have mainly black terga with narrow green apical margins (terga 2–3 medially almost completely black, Fig. 7a ). Furthermore, in the Russian specimen the black color on and beside the postocellar area, and on the occiput is clearly reduced ( Fig. 7 q). In addition, in the specimen from Kirov, the black line between the mesoscutellum and its appendage is missing ( Fig. 7 o), the mesopleural groove is not marked with black, and the femora of the front and middle legs are not continuously black-lined posteriorly as in the specimens from Finland.

Discussion. The species belongs in the group of R. viridis ( viridis , polaris , sibirica , californica s.l.). The angle of the incision behind the postcalcar (cypsella) is less than 45°, as usual in the group ( Figs 5e, f ). Furthermore, the densely sculptured appendage of the mesoscutellum and the shape of the frontal field agree with the usual character states in this group ( Fig. 7k ). The most distinctive external character of the species is the pale coloration of the head. The frontal ridges are not black in the lower part as in viridis and polaris , but green, in the holotype with an indistinct small dark pit in the lower part. A similar ‘ω’-like black marking is to be found in European Rhogogaster only in R. punctulata , but in this species the postocellar area is almost completely green, and the abdomen is much paler. Exceptionally (1♂ 1♀ of 340 examined specimens), very pale specimens of R. chlorosoma with similar head coloration occur. This form is dorsally much paler than magniserrula , the occiput is nearly completely pale (http:// dx.doi.org/10.6084/m9.figshare.1394863), and the genitalia are different.

In the eastern Palearctic R. sibirica (see below) the color of the head is even much paler than in magniserrula , and upper thorax and abdomen are nearly completely pale. Thus the amount of black on the head in the viridis group decreases in the order viridis ( Figs 4i –k ) – polaris (4l) – magniserrula (4n–p) – sibirica (4m).

The species is the most rarely collected European Rhogogaster . We cannot exclude, that undiscovered specimens of the species are mixed in larger collections under “ viridis ” in a broader sense. The coloration of the head should make it rather easy to recognize them.

Even though the male remains unknown, it seems not unlikely that it is similar to the female, and the general shape of its penis valves resembles that of viridis , polaris and sibirica .

Distribution. Fig. 6 p. The types were all collected in the boreal coniferous forest zone of NE Europe. The three records from Finland cover nearly the entire north-south extent of this country. Therefore, the species is at least to be expected in northern Sweden. The record from Kirov also suggests a more eastern distribution in northern Russia.

Etymology. The name magniserrula refers to the large serrulae of the saw and is to be treated as a noun.

Figures

FIGURE 4. a – x: head in dorsal view— a Rhogogaster punctulata, b R. chlorosoma, c R. chlorosoma (paratype), d R. scalaris (R. chlorosoma podkumokensis lectotype), e R. scalaris, f R. scalaris, g R. scalaris (R. carpatica lectotype), h R. scalaris, i R. viridis, j R. viridis (R. dryas paratype), k R. viridis, l R. polaris, m R. sibirica (lectotype), n R. magniserrula (holotype), o R. magniserrula (paratype from Russia), p R. magniserrula (holotype, oblique view), q R. robusta (holotype), r R. auctor (holotype), s R. naias (paratype), t R. bactriana (R. bactriana lindti paratype), u R. genistae (R. genistae viridifrons lectotype), v R. gilva (lectotype), w Tenthredo virescens (lectotype), x T. olivacea (R. viridis var. montana lectotype).

FIGURE 5. a – f: serrulae from the middle of the saw, with marked angle of cypsella— a – b Rhogogaster scalaris, c R. viridis, d R. polaris, e R. magniserrula, f R. magniserrula (worn). g – n: lancet (in h and k also lance) with details of serrulae— g, i, k R. polaris, h R. punctulata, j, l R. scalaris, m R. viridis, n R. magniserrula.

FIGURE 7. a – m: Rhogogaster magniserrula (holotype) — a dorsal view, b – c head and thorax dorsal view, d head and thorax laterally, e lance and lancet, f serrulae from the middle of the saw, g claw of hind leg, h hind tarsus, i 1 st – 3 rd plantar lobe, j face, k mesoscutellum and appendage in dorsolateral view, l labels, m antenna. n – r: R. magniserrula (paratype from Kirov) — n dorsal view, o head and thorax dorsolateral view p face oblique, q head dorsally, r labels.

FIGURE 6. a – j: penis valves— a – b Rhogogaster scalaris, c R. chlorosoma, d R. auctor (holotype), e R. punctulata, f R. polaris, g R. sibirica (paralectotype), h R. viridis, i R. naias (paratype). j – n: drawings of penis valves by Benson (1943, 1952, 1965) and Ross (1943) — j R. scalaris (as R. viridis), k R. chlorosoma, l R. punctulata, m R. californica, n R. viridis (as R. dryas). o: variability of penis valves in R. polaris (all from Sweden, Abisko area). p: records of R. magniserrula (displayed with Map data, © Basarsoft, Google).