Merodon natans (Fabricius, 1794)

Vujic, Ante, Tot, Tamara, Andric, Andrijana, Acanski, Jelena, Sasic Zoric, Ljiljana, Perez-Banon, Celeste, Aracil, Andrea, Veselic, Sanja, Arok, Maja, Mengual, Ximo, van Eck, Andre, Rojo, Santos & Radenkovic, Snezana, 2021, Review of the Merodon natans group with description of a new species, a key to the adults of known species of the natans lineage and first descriptions of some preimaginal stages, Arthropod Systematics & amp; Phylogeny 79, pp. 343-378 : 343

Merodon natans (Fabricius, 1794)

Syrphus natans Fabricius, 1794: 283.

Syrphus annulatus Fabricius, 1794: 296. syn. nov.

Syrphus melancholicus Fabricius, 1794: 302.

Diagnosis.

Merodon natans is a medium sized species (8-12 mm), which can be easily distinguished from M. calcaratus by its longer antenna (Fig. 2A, B ), broader metafemur in both sexes (Fig. 4A, B ) and the large, rounded posterior surstyle lobe of the male genitalia (Fig. 10A, B ) (in M. calcaratus posterior surstyle lobe narrow, fingerlike (Fig. 5A-G )). Morphologically it is closely related to M. makrisi sp. nov. and M. pulveris . Males of these species can be distinguished by the structure of the male terminalia: ventral margin of posterior surstyle lobe without visible triangular prominence from lateral view, although present in some specimens, but it is small and visible only from ventral view in M. natans (Fig. 10A, B ) (ventral margin of posterior surstyle lobe with clearly visible triangular prominence present in M. makrisi sp. nov. (Figs 8A :v, B:v, 10D:v) and M. pulveris (Fig. 10C :v)). Females of M. natans and M. pulveris are very similar, but the yellow pile, intermixed with some black pile on tarsomeres of proleg in M. natans can differentiate this species from M. pulveris (in M. pulveris tarsomeres of proleg covered with yellow pile only, except in some specimens with a very few black pile on the fifth tarsomere). Females of M. natans and M. makrisi sp. nov. can be separated based on the position of fossette, which is near the base of arista in M. makrisi sp. nov. (Fig. 2E, I :f) (in M. natans fossette position medially between the base of the arista and apex of basofagellomere (Fig. 2B, J :f)).

Type material.

Syrphus natans Fabricius: Type locality: Italy. Original Puparium description was based on an unspecified number of specimens. One appropriately labelled type was located in J.C. Fabricius collection ( ZMUC), but only a pin without any remaining parts of the specimen is present in the collection ( “193.20”). Consequently, we decided to designate a neotype because the type material has been destroyed. Neotype (designated here): ITALY: 1 ♂, Colli Berici, Unknown leg. (DS coll.), genitalia in a separate microvial with glycerine. Both basoflagellomere with arista glued to the locality label. Original labels: "Colli Berici (VI) / Viliaga - Pr. N. 132 / 45.384722°N 11.510000°E / 10-22 Aug. 2011", " Merodon / ♂ / natans / Det. Sommaggio 2011", “AU1861”, “24944”. - Syrphus annulatus Fabricius: Type locality: “Gallia” [France]. Original Puparium description was based on an unspecified number of specimens. Two syntypes were found in J.C. Fabricius collection ( ZMUC). Both specimens are partly destroyed, except for the remaining part of thorax and wings. Characters of both specimens match the definition of Merodon natans and we designated one of these specimens with a label as lectotype and the second specimen with a label as paralectotype. Designation of Syrphus annulatus lectotype was based on syntypes deposited in Copenhagen Museum ( ZMUC). The syntypes are partly destroyed, but the polinosity and pilosity of the mesoscutum clearly demonstrated that these specimens belong to the Merodon natans group. The synonymy with M. natans is based on distribution (France), where no other species from the M. natans group occur. Lectotype (designated here): FRANCE: sex unknown, original labels: “Gallia”, " annulatus ", "P 198.7 Bosc" [based on remaining body parts sex unclear] ( ZMUC). Paralectotype (designated here): FRANCE: sex unknown, original labels: “Gallia”, " annulatus ", "P 198.7 Bosc" [based on remaining body parts sex unclear] ( ZMUC). - Syrphus melancholicus Fabricius: Type locality: Italy. Original Puparium description was based on an unspecified number of specimens. One syntype was found in J.C. Fabricius collection ( ZMUC). Characters of the syntype match M. natans and it is designated as lectotype. Lectotype (designated here): ITALY: 1 ♂, original labels: " melancholicus ", “245.58” ( ZMUC). - Other studied material. Published in Arok et al. (2019); SPAIN: 1 ♂; Soria, Miño de Medinaceli; 28 Aug. 1984; M.A. Marcos-García leg.; published in Marcos-García (1988). - Additional material examined. CROATIA: 1 ♀; Island Cres, env. Cres; 8-10 Sep. 2009; J. Halada leg.; FSUNS ID 25463 (MB coll.) 1 ♀; Nos Kalik, Krka N.P.; 43.8175°N, 15.9913°E; 130 m a.s.l.; 1 Oct. 2017; A. van Eck leg.; AvE coll. - GREECE: 1 ♂; Iraklia, Ageli; 36.8420°N, 25.4609°E; 21 Oct. 2018; J. Gavalas leg.; FSUNS ID 25448 (MAegean) 6 ♀♀; same data as for preceding; FSUNS ID 25449 to 25454 (MAegean) 1 ♀; Iraklia, Merichas; 36.8284°N, 25.4686°E; 28 Oct. 2018; J. Gavalas leg.; FSUNS ID 25455 (MAegean) 1 ♀; Crete, Asteri near Skala-Elos; 23-25 Apr. 1956; Brochmann leg.; ZFMK-DIP-00076213 ( ZFMK) 1 ♀; Crete, Agia Galini, Fourfouras; 9 Oct. 1992; N. Chalwatzis leg.; ZFMK-DIP-00076212 ( ZFMK) 2 ♂♂; Kefalonia, 1 km W of Fiskardo; 50 m a.s.l.; 5 Oct. 1994; S.M. Blank leg.; ZFMK-DIP-00076209, ZFMK-DIP-00076210 ( ZFMK) 1 ♂; Kefalonia, 1 km W of Poriarata, near Vlachata; 150 m a.s.l.; 9 Oct. 1994; S.M. Blank leg.; ZFMK-DIP-00076206 ( ZFMK) 2 ♀♀; same data as for preceding; ZFMK-DIP-00076207, ZFMK-DIP-00076208 ( ZFMK) 1 ♂; 42 km SW of Gythio, Cape Tenaro; 16 Oct. 1994; S.M. Blank leg.; ZFMK-DIP-00076211 ( ZFMK). - ITALY: 1♀; Sardinia, Siniscola, Pineta; Apr. 1989; M. Hauser leg.; ZFMK-DIP-00069590 ( ZFMK). - SERBIA: 1 ♀; Pčinja, Vogance; 42.3451°N, 21.9159°E; 513 m a.s.l.; 11 Sep. 2020; A. Vujić, L. Likov, T. Tot, M. Ranković leg.; on Mentha sp.; FSUNS ID 32714 ( FSUNS) 2 ♂♂, Pčinja, Donja Trnica; 42.3840°N, 22.0525°E; 11 Sep. 2020; A. Vujić, L. Likov, T. Tot, M. Ranković leg.; on/near Prospero autumnale ; FSUNS ID 32720, 32724 ( FSUNS) 3 ♀♀; same data as for preceding; FSUNS ID 32721 to 32723 ( FSUNS) 1 ♀; same data as for preceding; 15 Sep. 2020 a female reared from pupa collected 11 Sep. 2020 in Prospero autumnale bulb by A. Vujić; FSUNS ID 34373 ( FSUNS).

Redescription.

Male (Fig. 11A, C ). Head: Antenna: dark brown; basal part of arista light brown; in some specimens basoflagellomere light brown; basoflagellomere two times as long as wide. Face: Black, white pollinose; covered with long white pile as long as pedicel, except for medial vitta extending from base of antenna to lower part of face without long white pile; ventral part of face and anteroventral part of gena black, shiny; frontal triangle black, white pollinose, covered with long white pile as long as pedicel; eyes holoptic, covered with white pile; vertical triangle isosceles black, shiny except for anterior part to anterior ocellus and posterior part to posterior ocelli white pollinose; vertical triangle covered with long white pile as long as pile on frontal triangle and intermixed black pile on ocellar triangle; ocellar triangle equilateral; occiput black, white pollinose covered with white pile as long as pile on vertical triangle. Thorax: Scutum black, with five white pollinose vittae; covered with white erect pile as long as pile on occiput and short, black adpressed pile on area between transverse suture and scutellum; short black bristles present above wing base; scutellum black, covered with long white pile as long as pile on scutum; pleura black, white pollinose; dorsal part of anterior anepisternum, posterior anepisternum, anterior anepimeron, dorsomedial part of anepimeron with long, dense white pile as long as pile on scutum; long white pile on katepisternum broadly separated with bare area between; proepimeron and katatergum with some white pile. Legs: Femora black, yellow only at base and apex, covered with white pile, some black pile presented on its apical part; metafemur swollen with serrated triangular lamina (Fig. 4A ); tibiae yellow medially darkened, covered with white pile; colour of tarsomere dorsally varies from yellow to dark brown, ventrally yellowish; tarsomeres mainly covered with white pile, intermixed with some black pile. Wing: Hyaline, covered with microtrichia except for some bare areas in first and second basal cells; stigma light yellow; wing veins dark brown, basally yellowish; halter and calypter yellow. Abdomen: Black, slightly tapering; tergum 2 with anterolateral reddish maculae, in some specimens anterolateral reddish maculae on tergum 2 absent; terga 2-4 with white pollinose fasciae; pollinose fasciae on tergum 2 widely separated, on terga 3-4 in some specimens may merge; lateral margin of abdomen blackish covered with white pollinosity, in some specimens lateral margin of abdomen yellowish; posterior margin of terga 3-4 yellowish; terga covered with adpressed black and white pile, shorter than pile on scutum; white pile on lateral margin of abdomen longer than pile on terga; sternum 1 dark brown; colour of sterna 2-4 varies from dark brown to light brown; sterna covered with long, white erect pile longer than pile on terga. Male genitalia: Epandrium (Fig. 10A, B ): posterior surstyle lobe rounded, ventral margin of posterior surstyle lobe without visible triangular prominence from lateral view, although it can be present in some specimens, but it is small and visible only from ventral view; anterior surstyle lobe on inner side oval shaped, covered with dense, short white pile. Hypandrium: as in other members of Merodon natans group, hypandrium broaded medially. Female (Fig. 11B, D ): Similar to male except for normal sexual dimorphism. Frons black covered with white pollinosity, except for black shiny vitta extending from lunule to anterior ocellus.

Variability.

The posterior surstyle lobe in males of M. natans varies in shape, as in the case of M. calcaratus , but is less distinct. In the Montenegro (Boka Kotorska) population of M. natans and in a single specimen from Spain, the posterior surstyle lobe is narrower (Fig. 10B ).

Distribution.

Merodon natans occurs in most countries of southern Europe (Spain, Italy, Croatia, Serbia, Bulgaria, North Macedonia, Montenegro, Greece) and part of western Europe (France) (Fig. 6 ). According to Marcos-García et al. (2007) and Speight (2020), M. natans is recorded from Israel and the Caucasus. However, the records of M. natans from Israel refer to M. neolydicus Vujić in Vujić et al. (2018b) and M. makrisi sp. nov. described in this paper. We can here anticipate that specimens from the Caucasus will also likely refer to another Merodon species.

Biology.

Preferred environments are forests with open ground; herb-rich open areas in thermophilous Quercus forest and phrygana with Cistus scrub; also in orchards in southern Europe ( Speight 2020). Adults prefer open areas with tall herbs and scrub (Fig. 11A, B, E ), within dry woodland; a secretive species, as easily collected by use of Malaise traps as by direct observation ( Speight 2020). Flowers visited include: Prospero autumnale (Fig. 11C, D ), Foeniculum sp., Mentha sp., Solidago sp., Drimia maritima . The flight period is in Spring (April/May) and Autumn (end August/beginning October). The puparium, described here, is found in the host plant Prospero autumnale in Serbia (Fig. 11C, D ).

Additional remark.

This study revealed that records from Portugal ( van Eck 2016) were based on incorrect identifications. At present, M. natans is not confirmed for the Portuguese fauna and should be removed from its checklist.

Figures

Figure 2. Antenna. A, B, J Merodon natans C, D, K M. pulveris E, F, I M. makrisi Vujic, Radenkovic & Tot sp. nov. G, H M. calcaratus; A, C, E, G male B, D, F, H-K female; A-H lateral view I-K dorsal view; A Greece (Olimp) B Greece (Achaia) C, D Turkey E, F, I Cyprus G, H Spain J Greece (Alexandroupoli) K Turkey. Scale bar: 0.2 mm.

Figure 4. Metaleg without tarsomeres, lateral view. A, B Merodon natans C, D M. pulveris E, F M. makrisi Vujic, Radenkovic & Tot sp. nov. G, H M. calcaratus; A, C, E, G male B, D, F, H female; A Italy (Sicily) B Croatia C, D Turkey E, F Cyprus G Algeria H Tunis. Scale bar: 1 mm.

Figure 5. Merodon calcaratus epandrium, lateral view. A Morocco B, D Algeria C Tunis E left surstyle of specimen from Kenya F Kenya G Spain. Arrow marks invagination on ventral margin of surstyle. Scale bar: 0.2 mm.

Figure 6. Distribution map of the species of Merodon natans group.

Figure 8. Merodon makrisi Vujic, Radenkovic & Tot sp. nov. male genitalia, Cyprus. A epandrium B left surstyle C, E hypandrium D aedeagus and associated structures; A, C, D lateral view B, E ventral view. Abbreviations: a - anterior surstyle lobe, aa - aedeagal apodeme, ae - aedeagus, c - cercus, ea - ejaculatory apodeme, la - lateral sclerite of aedeagus, n - notch on theca to which is attached the aedeagal apodeme, p - posterior surstyle lobe, v - triangular prominence on ventral margin of posterior surstyle lobe. Scale bar: 0.2 mm.

Figure 10. Epandrium, lateral view. A, B Merodon natans C M. pulveris D M. makrisi Vujic, Radenkovic & Tot sp. nov. Abbreviation: v - triangular prominence on ventral margin of posterior surstyle lobe; A Greece (Achaia) B Montenegro C Greece (Rhodes) D Cyprus. Scale bar: 0.2 mm.

Figure 11. Merodon natans in a Serbian habitat. A, C male B, D female E typical habitat where M. natans can be collected. Photos: T. Tot, 11 Sep. 2020.