Andrena (Euandrena) sesmae Wood, Cornalba & Praz, 2023

Wood, Thomas James, Praz, Christophe, Selis, Marco, Flaminio, Simone, Mei, Maurizio, Cornalba, Maurizio, Rosa, Paolo, Divelec, Romain Le & Michez, Denis, 2023, Revisions to the Andrena fauna of Italy, with the description of a new species (Hymenoptera: Andrenidae), Fragmenta entomologica 55 (2), pp. 271-310 : 291-296

publication ID	https://doi.org/ 10.13133/2284-4880/1542
persistent identifier	https://treatment.plazi.org/id/ED6C878F-BF5F-216A-C326-0E40FE27F8AA
treatment provided by	Felipe
scientific name	Andrena (Euandrena) sesmae Wood, Cornalba & Praz
status	sp. nov.

Treatment

Andrena (Euandrena) sesmae Wood, Cornalba & Praz , sp. nov.

HOLOTYPE: ITALY: UMBRIA: 1♀, Attigliano ( TR), Fi- ume Tevere , 50 m, 42.509 oN, 12.279 oE, 17 Mar 2023 [type locality between the two provinces of Terni (Umbria) and Viterbo (Lazio) on the bed of the river Tiber), leg. M. Selis ( OÖLM) (BOLD accession number WPATW998-23).

PARATYPES: ITALY: LOMBARDY: 6♀, Milano, Niguarda , 19 Mar 1922, leg. L. Micheli ( MSNM) ; 3♀, Milano , 29–30 Mar 1922, leg. L. Micheli ( MSNM) ; 2♀, Monza , 12 Mar 1922, leg. L. Micheli ( MSNM) ; 4♀, Cecima ( PV) , 440–690 m, 2 Jun 2018, leg. M. Cornalba ( CPC / MCC) ; 1♀, ibidem, 18 Mar 2019, leg. M. Cornalba ( MCC) ; 1♀, ibidem, 9 Jun 2019, leg. M. Cornalba ( MCC) ; 1♀, ibidem, 30 May 2020, leg. M. Cornalba ( MCC) ; 2♀, ibidem, 6 Jun 2023, leg. M. Cornalba ( MCC) ; 1♀, ibidem, 17 Jun 2023, leg. M. Cornalba ( MCC) ; EMILIA-ROMAGNA: 1♀, Bologna, Ronzano , 16 Jun 1935, leg. G. Grandi, IEUB . UMBRIA: 4♂, Castel Viscardo, 10 km NW of Orvieto , 30 May– 7 Jun 1991, leg. J. Gusenleitner, ( OÖLM) . LAZIO / UMBRIA: 1♀ , Lazio ( VT) / Umbria ( TR) , Tevere, Bomarzo / Attigliano , 50 m, 17 Mar 2023, leg. M. Selis ( TJWC) ; 1♂ 1♀, ibidem, 15 Feb 2023, ( MSVI) . LAZIO: 1♂, Norchia ( VT) , 125–160 m, 5 Mar 2021, leg. M. Selis ( TJWC) ; 1♂, ibidem, 19 May 2022 ( OÖLM) ; 1♂, ibidem, 10 Mar 2022 ( TJWC) ; 1♂, ibidem, 26 Feb 2021 ( TJWC) ; 3♀, ibidem, 28 Feb 2021 (MSVI/ TJWC) ; 1♂, ibidem, 5 Mar 2021 ( MSVI) ; 1♂, ibidem, 25 Mar 2021 ( MSVI) ; 1♀, Maccarese ( RM) , 30–65 m, 4 Mar 2020, leg. M. Selis ( MSVI) .

Diagnosis. Andrena sesmae sp. nov. can be placed in the subgenus Euandrena due to the narrow facial foveae, occupying slightly less than one third of the space between the compound eye and a lateral ocellus, the foveae narrowing further ventrally, pronotum without humeral angle, A3 long (clearly exceeding A4+5), and the predominantly simple hairs of the tibial scopae (hairs not strongly plumose as in the subgenus Chrysandrena Hedicke, 1933 ).

Diagnosis to species level is challenging due to the high degree of taxonomic complexity within the subgenus Euandrena ( Praz et al. 2019; Wood 2023a; b). Genetic analyses suggest that A. sesmae sp. nov. is clearly distinct from A. bicolor Fabricius, 1775 s. l. (that is, the two clades found within A. bicolor and discussed in Schmidt et al. 2015, Praz et al. 2019, Gueuning et al. 2020), including Andrena bicolor apricaria Warncke, 1975 , of unclear status. Genetic distance between A. sesmae and A. bicolor were on average 6.23% (range 5.09–7.74%). Andrena sesmae was part of a well-supported clade ( Fig. 9 View Fig ) containing three monophyletic lineages: one lineage including all Italian specimens, attributed to A. sesmae , and two lineage each containing sequences from Greece and Jordan. One of these lineages was previously referred to as Euandrena sp. 3 ( Praz et al. 2019), and can provisionally be referred to as A. rufitibialis Friese, 1899 . The second lineage can be tentatively referred to as A. glidia Warncke, 1965 . Although not included here, both clades are present in Israel (G. Pisanty, pers. comm., unpublished data), indicating that these two mitochondrial lineages are widespread in the East Mediterranean. The average genetic distance between these two lineages was 5.47% (4.92–6.28%). These two lineages are morphologically variable and future research is needed to determine whether they represent two distinct species, and how to consistently recognise them morphologically. As in the case of A. bicolor , they are both referred to as A. rufitibalis s. l. for now. The genetic difference between these two lineages and A. sesmae was 4.05% (3.04–5.64%), but A. sesmae is morphologically distinct from both lineages and is therefore recognized as a distinct species. Genetic distances within A. sesmae were on average 0.32% (0.00–1.40%). Diagnosis is therefore made to these lineages, as well as to A. bicolor , to which A. sesmae is not immediately related.

Recognition of A. sesmae sp. nov. requires the use of a combination of characters, and also the recognition that pubescence colour is highly variable, and no individual pubescence character can be used in isolation. In the female sex, A. sesmae should be recognised by the facial pubescence which is often extensively pale with black hairs restricted to the inner margins of the compound eye ( Fig. 10A View Fig ), or the clypeus ( Fig. 10C View Fig ). This contrasts A. bicolor which typically displays abundant black hairs on the face, either entirely black or usually with some sparse pale hairs also present around the antennal insertions or on the frons. Some A. sesmae converge on this colour pattern, with very dark individuals showing only scattered ginger hairs around the antennal insertions ( Figs 10E, G View Fig ). The same pattern is seen for the pubescence of the mesepisternum, which can be extensively pale ( Figs 10B, D View Fig ), but can also display many black hairs ( Figs 10F, H View Fig ), and hence approaches the condition of A. bicolor which usually displays abundant black hairs on the mesepisternum. In addition, A. sesmae (and A. rufitibialis s. l.) have a fringe of light grey hairs along the margin of T2-T4; in A. bicolor s. l., the same fringe of hairs is less dense, and usually darker, typically yellowish brown in fresh specimens. The scutum of A. sesmae also has numerous, short dark hairs beneath the longer light hairs, a condition rarely observed in A. bicolor in central Europe. Some individuals of A. sesmae from the Milan region show the hind tibiae and basitarsi partially lightened orange ( Fig. 11F View Fig ). This may result in some confusion with A. ruficrus Nylander, 1848 , but this latter species has the facial foveae short and broad, not clearly narrowing ventrally, and the mesepisternum lacks black hairs, whereas in the only individuals of A. sesmae with light orange hind tibiae, the mesepisternum shows abundant black hairs; in addition, the tergal discs are shagreened and very finely punctate in A. ruficrus , contrasting with the condition in A. sesmae .

Pale individuals of A. sesmae sp. nov. (with abundant pale hairs on the face and mesepisternum) resemble A. rufitibialis s. l. The key point of difference that allows separation, and which also allows separation from A. bicolor , is that the scutum is covered entirely with strong and dense granular shagreen, and is almost entirely dull. The surface is punctate, but the punctures are relatively shallow, and are typically separated by 0.5–1 puncture diameters except medially where they can be separated by up to 3 puncture diameters ( Fig. 11C View Fig ). In comparison species, the scutum is usually at least partially shiny, sometimes extensively so, and scutal punctures are usually stronger, more distinct, and slightly denser (the holotypes of the additional East Mediterranean comparison taxa A. rufitibialis limosa Warncke, 1975 and A. robusta Warncke, 1975 also display a shiny scutum; the status of these taxa remains to be established). Andrena sesmae can therefore be recognised in an Italian context by the typically pale hair of the face and mesepisternum combined with the uniformly strongly shagreened and dull scutum with obscure punctation. However, some barcoded specimens of A. bicolor from Lebanon (e.g. WPATW1138-23) show a scutum that is almost equally dull, with shining areas greatly reduced; it is clear that extreme care must be taken in this complex group, including the use of molecular data whenever possible.

Males of sesmae sp. nov. are, as always in the subgenus Euandrena , more challenging to recognise. The combination of face with intermixed black and white hairs, mesepisternum with intermixed black and white hairs, and scutum with strong and dense granular shagreen, almost entirely dull (as in the female sex) should allow recognition. However, there is a great deal of variation in pubescence colouration. For the facial hair, it can vary from a more or less even mix of black and white ( Fig. 12C View Fig ) to entirely black ( Fig. 12D View Fig , thus resembling males of A. bicolor ), to extensively white ( Fig. 12E View Fig ). The same goes for the mesepisternum which is typically a mixture of black and white ( Fig. 13A View Fig ), but can be entirely covered with black hairs ( Fig. 13B View Fig ). As for females, the key character is the uniformly shagreened and dull scutum. This combination of characters should allow recognition in most cases, though consultation of barcoded material should be made for the highest degree of confidence.

Description: Female: Body length: 8.5–9.5 mm ( Fig. 11A View Fig ). Head: Dark, 1.2 times wider than long ( Fig. 11B View Fig ). Clypeus weakly domed, densely but shallowly punctate, punctures separated by <0.5–0.5 puncture diameters, underlying surface strongly shagreened, dull. Process of labrum rounded triangular, 2.5 times wider than long, surface with weak wrinkles, predominantly shining. Gena slightly exceeding width of compound eye; ocelloccipital distance slightly exceeding diameter of lateral ocellus. Foveae dorsally narrow, occupying ⅓ of space between compound eye and lateral ocellus, equalling width of flagellum, slightly narrowing further ventrally at level of antennal insertions; foveae filled with dark brown hairs. Face with variable pubescence, palest forms with abundant pale hairs covering majority of face, with black hairs restricted to inner margins of compound eyes ( Fig. 10A View Fig , 11B View Fig ), sometimes extending onto clypeus ( Fig. 10C View Fig ). Darker forms with face predominantly covered by black hairs, with ginger hairs around antennal insertions and on frons ( Figs 10E, G View Fig ). Gena and vertex equally variable, with predominantly pale or predominantly dark pubescence; facial hair moderately long, none equalling length of scape. Antennae basally dark, A5– 12 ventrally slightly lightened by presence of grey scales; A3 exceeding A4+5, shorter than A4+5+6.

Mesosoma : Scutum uniformly covered with strong and dense granular shagreen, and almost entirely dull, surface shallowly punctate, punctures separated by 0.5–1 puncture diameters, medially separated by up to 3 puncture diameters ( Fig. 11C View Fig ). Pronotum rounded. Mesepisternum with granular microreticulation, dull. Dorsolateral parts of propodeum with fine granular microreticulation, sculpture overlain with sparse network of raised rugosity forming appearance of large shallow punctures with raised rims, pseudopunctures separated by 0.5–1 puncture diameters. Propodeal triangle narrow, laterally finely delineated by faintly raised narrow carinae, internal surface with granular microreticulation without pseudopunctures, basally with irregular weakly raised rugae; propodeal triangle thus defined by change in surface sculpture. Mesepisternum with variable pubescence, from predominantly covered with long light brown hairs with only scattered black hairs ( Figs 10B; 10D View Fig ) to intermixed ginger and black hairs ( Fig. 10F View Fig ) to predominantly black haired ( Fig. 10H View Fig ). Propodeal corbicula incomplete, dorsal fringe loosely formed, composed of light brown plumose hairs, internal surface with numerous plumose hairs. Legs usually dark ( Fig. 10E View Fig ), hind tibiae and basitarsi sometimes lightened orange ( Fig. 10F View Fig ); pubescence of legs light to dark brown. Flocculus complete, composed of light brown plumose hairs; femoral and tibial scopae composed of golden-orange partially plumose hairs, comprising a mixture of simple and weakly plumose hairs. Hind tarsal claws with inner tooth. Wings hyaline, stigma and venation dark brown, nervulus interstitial.

Metasoma: Tergal discs dark, apical margins narrowly lightened hyaline yellow-brown, underlying surface shagreened, weakly shining. Tergal discs irregularly punctate, punctures separated by 1–2 puncture diameters, on T1 punctures with partially raised rims, resembling crater punctures; marginal areas more or less punctate. Tergal discs with long erect hairs, basally pale to light reddish-brown, apically with increasing abundance of shorter black hairs on discs of T3–4; T1–4 apically with brown- ish-grey hairs forming weak complete apical hairbands, not obscuring underlying surface, most clearly produced on T3–4 ( Figs 11E–F View Fig ). Apical fringe of T5 and hairs flank- ing pygidial plate dark brown. Pygidial plate rounded triangular, surface weakly shining, featureless.

Male: Body length: 8–9 mm ( Fig. 12A View Fig ). Head: Dark, 1.25 times wider than long ( Fig. 12B View Fig ). Clypeus weakly domed, broadly flattened medially, surface densely but shallowly punctate, punctures separated by <0.5–0.5 puncture diameters, underlying surface strongly shagreened, dull. Process of labrum rounded trapezoidal, 2–2.5 times wider than long, anterior margin truncate, humped, emarginate. Gena slightly exceeding to exceeding width of compound eye; ocelloccipital distance 1.5 times diameter of lateral ocellus. Facial pubescence variable, from mixed black and white ( Fig. 12C View Fig ) to entirely black ( Fig. 12D View Fig ) to predominantly white with black hairs restricted to inner margins of compound eyes and apex of clypeus ( Fig. 12E View Fig ); gena and vertex equally variable, facial pubescence long, longest hairs exceeding length of scape. Antennae dark basally, A4–13 ventrally lightened by presence of grey scales; A3 exceeding A4, shorter than A4+5, A4 quadrate, only lightly longer than broad, A5–13 rectangular, clearly longer than broad.

Mesosoma : Mesosoma structurally as in female ( Fig. 12F View Fig ). Mesepisternum with pubescence variable, from covered with intermixed black and white hairs ( Fig. 13A View Fig ) to entirely covered with black hairs ( Fig. 13B View Fig ); hairs exceeding length of scape. Scutum and scutellum with pubescence variable, from white to orange-brown. Legs dark, pubescence whitish. Hind tarsal claws with inner tooth. Wings hyaline, stigma and venation dark brown, nervulus interstitial.

Metasoma: Terga structurally as in female, pubescence more scattered, T2–4 with very weak apical hairbands composed of long sparse hairs, not obscuring underlying surface ( Fig. 13C View Fig ). T6-7 with long brown hairs overlying pseudopygidial plate. S8 narrow, columnar, ventral surface covered with spreading dark brown hairs. Genital capsule simple, gonocoxae apically produced into slight rounded bumps, gonostyli narrow, slightly broadened apically, spatulate, inner margins slightly raised ( Fig. 13D View Fig ). Penis valves narrow, more or less par- allel-sided though medially constricted, occupying ¼ of space between gonostyli.

Remarks. The species appears to be bivoltine, with the first generation in March (and presumably early April) and the second generation at the end of May into June. All of the second-generation females observed at the Cecima site were collecting pollen on Campanula rapunculus ( Campanulaceae ), except one that was collecting on Loncomelos brevistylus (= Ornithogalum pyramidale auct.; Asparagaceae ). The only first-generation female observed at the site was collected on Crepis sancta ( Asteraceae ).

Etymology. From Sésma, the name of Cecima in the local dialect. Cecima is the village in the northern foothills of the Ligurian Apennines (SW Lombardy) in whose vicinity this species was first detected by one of us (MC). The name takes the genitive form.

Distribution. Northern and central Italy (Lombardy, Emilia-Romagna, Umbria, Lazio).