Stenostoma rostratum Fabricius, 1787

Poloni, Riccardo, Bologna, Marco A. & Riccieri, Alessandra, 2024, One genus, four different stories: evolutionary history, bionomics and biogeography of the monotypic tribe Stenostomatini (Coleoptera: Oedemeridae), Zoological Journal of the Linnean Society 200 (3), pp. 705-719 : 715-716

Stenostoma rostratum Fabricius, 1787

(F I G S 1D, E, I, L, 2G–M, 6E, F)

Rhinomacer caeruleus Petagna, 1787 Specimens Insectorum ulterioris. Calabriae – 144, pl. 72, fig. 34 (nomen praeoccupatum by Rhinomacer coeruleus Geoffroy in Fourcroy, 1785: 114).

Leptura rostrata – Fabricius 1787 Mantissa Insectorum, 1: 159, 23.

Necydalis ceramboides – Rossi 1794,: 99 (nomen praeoccupatum by Necydalis ceramboides Forster 1771: 47 ).

Stenostoma rostratum – Latreille 1810: 217.

Stenostoma coeruleum – Seidlitz 1899: 5: 964.

Stenostoma coeruleum schatzmayri – Magistretti 1941: 77; Bologna 1981: 212.

Stenostoma coeruleum coeruleum – Bologna 1981: 207, figs 1, 3–9.

Stenostoma rostratum – Vazquez 1993: 118; Vazquez 2002: 106, 178 Fig. b.

Stenostoma rostratum rostratum – Švihla 2005: 72.

Stenostoma rostratum septentrionale – Švihla 2005: 72.

Type locality: Rhinomacer coeruleus : [Calabria, Italy]Brancaleone; L. rostrata : [ Algeria] Ammi Moussa [according to Švihla 2005; but this interpretation is questionable, with this locality being far from the coast, and also the note (‘ Ammi mains Africae Dom. Vahl’.) by Linnaeus could indicate on plants of Ammi ( Apiaceae ), along the African seas (‘mains’); in any case, the type locality can be identified along the Maghreb coasts where Vahl collected]; N. ceramboides [Tuscany, Italy]: Etruria; S. c. schatzmayri: [ Israel] Tel Aviv; S. r. septentrionale : not specified.

Type specimens: We examined one paratype of the form S. c. schatzmayri ( MVR) .

Short description: For an extended description, see Mulsant (1858), Bologna (1981) and Švihla (2005). Body length: 7–12 mm. Colour of the body blue or greenish. Head distinctly rostrate, twice as long as wide ( Fig. 1I, L ). Pronotum subcylindrical, slightly enlarged at the base and at two-thirds of its length and protruding anteriorly ( Fig. 1I, L ). Aedeagus long and thin, only slightly narrowed towards the apex, similar to S. melitense but less curved ( Figs 2H, L, M ). The shape of the aedeagus is variable in both subspecies.

Taxonomic notes: Latreille (1810), describing the new genus Stenostoma , ascribed to it Leptura rostrata , but this binomial association was not used in the literature for several years. Vazquez (1993) first evidenced that the name Rhinomacer caeruleus was preoccupied and consequently resurrected Latreille’s binomial.

According to Švihla (2005), the species is polytypic, and the nominate form is distributed in the southern Iberian Peninsula, north-western Africa (from Morocco to Tunisia), Israel, Sporades islands and Crete, but is apparently absent from in Libya and Egypt, two countries relatively well explored. The form S. c. schatzmayri was simply considered as a synonym of the nominotypical subspecies by Švihla (2005). The subspecies S. r. septentrionale was not described formally by Švihla (2005), and neither types nor type locality were specified, but it was considered only as a new name for R. caeruleus . It is distributed along the northern coasts of the Mediterranean (from Spain to Italy and the Tyrrhenian islands, Croatia, Montenegro, Corfu and the Peloponnese). No information on the taxonomic position of the Atlantic populations ( Morocco, Portugal, Spain and France) was proposed by Švihla (2005).

The supposed two subspecies are very similar ( Švihla 2005): the nominotypical one has finer sculptured elytra and shorter elytral pubescence than the subspecies S. r. septentrionale , but the difference in pubescence is subtle and can be seen only by examining numerous specimens. In some samples we examined, these differences were not recognizable and no difference in genitalia or other characters were found, even when examining numerous specimens from multiple localities. We consider that the variability of the sculpture and the pubescence can be ascribed to the intraspecific variability of a species displaying a wide range and a moderately wide morphological variability, wuch as S. rostratum . Other traits that vary in a considerable way are as follows: (i) size (7–12 mm); (ii) colour of integument (from metallic green to metallic blue); (iii) sculpture of pronotum (from deeper and denser punctures to shallower and scattered); (iv) shape of the pronotum (more or less enlarged at the base and at two-thirds of its length); and (v) male genitalia, especially the apex of the aedeagus (slender and more acuminate to bulkier and rounder) ( Figs 2H, L, M ).

For these reasons and because no molecular differences were detected among the examined populations, we consider the species as monotypic, with slightly different setation in northern and southern populations, and propose the following synonymy: Stenostoma rostratum septentionale Švihla, 2005 = Stenostoma rostratum ( Fabricius, 1787) syn. nov.

Distribution: Stenostoma rostratum is distributed with scattered populations in almost all well-preserved dune coasts of the western Mediterranean and more disjointly along the south-eastern and eastern coasts of the Basin: Portugal, Spain, France, Italy, Croatia, Montenegro, Albania, Greece (apparently only in Corfu, Peloponnese, Crete and Sporades), Morocco, Algeria, Tunisia, Israel and Cyprus (Kubisz and Iwan 2020), but we did not examine specimens from the last country. It has also been recorded from the Atlantic coasts of Portugal, Spain and western France (north to Brittany) and of Morocco (South to Essaouira) ( Fig. 3 ). According to Magistretti (1963), it is also distributed along the Black Sea Russian coasts, from where we did not examine material; Kubisz and Iwan (2020) did not consider this citation.

Ecology: Stenoecious and halophilic element, strictly related to well-preserved coastal fore-dunes ( Fig. 6E, F ), considered as an indicator of good quality of this endangered ecosystem ( Bologna 1981, Agullo and Prieto 2012). Champion (1891) erroneously indicated its presence in marshy habitats. Its presence is restricted to the first 30 m of frontal, dynamic and embryonic dunes, where are spread only herbaceous plants, usually referable to the ‘Cakiletum’ and ‘Elymetum’ associations (see Biondi et al. 1986).

This species can be considered as an oligophagous element, feeding on Eryngium maritimum L., Echinophora spinosa L. ( Apiaceae ) and Anthemis maritima L. ( Asteraceae ) ( Binaghi 1964, Bologna 1977, 1984, Vazquez 1993, Montalto and Bologna 2011), and rarely recorded on other flowers of the same ecosystem, such as Cakile maritima Scopoli and Achillea maritima L. ( Mulsant 1858, Biondi et al. 1986, Vazquez 1993; authors' observation).

The short courtship and copulation, both with the male dorsal in position on the female, were observed on the host flowers in different localities of Italy (observation by the authors.) and in laboratory conditions (Supporting Information, Fig. S3 ; see Results).

The ascertained phenology is April–August (observation by the authors; Magistretti 1941, Binaghi 1964, Bologna 1977; Supporting Information, Table S2).

Perris (1877) briefly described the larva of this species by comparison with that of Oedemera flavipes (Fabricius, 1792) and considered it as developing in the roots and the basal stem of Eryngium maritimum and Achillea maritima ( Perris 1857, 1877). In contrast, Caillol (1919) supposed that the larva develops inside bollards standing in sea water, whereas Bologna (2010) and Montalto and Bologna (2011), on the base of personal observation in Sardinia (Is Arenas of Narbolia, Oristano province, M.A.B.) noted adults ovipositing on soaked or dried driftwood transported by the sea on the seashore. We also made a similar observation (A.R. and M.A.B., pers. obs.) in the same Sardinian locality of Is Arenas and in Porto Ferro (Sassari province) in June 2021. By rearing female and male individuals of S. rostratum in laboratory conditions (as explained in the Materials and Methods and the Results), we demonstrated that larvae develop within driftwood. Larvae obtained from laboratory experiments will be the object of a separate morphological contribution.

Figures

Figure 1. Habitus and detail of head and pronotum of the species within the genus Stenostoma. A–E, habitus. A, Stenostoma cossyrense. B, Stenostoma lowei. C, Stenostoma melitense. D, Stenostoma rostratum rostratum. E, Stenostoma rostratum septentrionale. F–L, detail of head and pronotum. F, S. cossyrense. G, S. lowei. H, S. melitense. I, S. rostratum rostratum. L, S. rostratum septentrionale.

Figure 2. Genitalia of the species within the genus Stenostoma. A, B, Stenostoma cossyrense tegmen (A) and aedeagus (B). C, D, Stenostoma lowei tegmen (C) and aedeagus (D). E, F, Stenostoma melitense tegmen (E) and aedeagus (F). G, H, Stenostoma rostratum rostratum tegmen (G) and aedeagus (H). I–M, Stenostoma rostratum septentrionale tegmen (I) aedeagus (L) and aedeagus, variability (M).

Figure 3. Distribution map of the tribe Stenostomatini. Key:white dots, Stenostoma rostratum; purple dots, Stenostoma lowei; green dots, Stenostoma cossyrense; orange dots, Stenostoma melitense.

Figure 6. Biotopes of the species within the genus Stenostoma. A, Pantelleria, Piano Ghirlanda (Stenostoma cossyrense). B, Madeira, Eira do Serrado, Madeira (Stenostoma lowei). C, Sicily, Punta Braccetto, stabilized dunes (Stenostoma melitense). D, Malta, Gozo Island (S. melitense). E, Sicily, Punta Braccetto, dunes (Stenostoma rostratum). F, Sardinia, Porto Ferro (S. rostratum, habitat and oviposition site with dead wood).