Rhizophagus diaboli, Dodelin, 2021

Barnouin, Thomas, Vincent, Alexis & Soldati, Fabien, 2025, Rhizophagus atticus Tozer, 1968 in France: synonymy with R. diaboli Dodelin, 2021, distribution and ecology (Coleoptera: Monotomidae), Zootaxa 5691 (2), pp. 329-340 : 335-336

Rhizophagus diaboli compared with R. atticus

The shape of the antennal club is not a valid character to discriminate between R. diaboli and R. atticus . Although Tozer (1968) and Dodelin (2021) described the club of R. atticus as spherical, the type specimens of R. atticus consistently show a subtruncate antennal club with the 11 th antennomere embedded into the 10 th ( Fig. 11 ), thus falling within the range of variability observed in R. diaboli ( Fig. 12 ). The photos of this character by Nikolopoulos (1969) are consistent with our observations.

Body size is not a distinguishing feature between both species either. Dodelin (2021) maintains that R. atticus is smaller (2.0–2.8 mm) than R. diaboli (3.0–4.0 mm). However, it was based on an examination of only 10 specimens in total for both species. It is also regrettable that for R. atticus he relied only on the measurements presented by Tozer (1968), omitting the more extensive measurements (2.5–3.8 mm) presented by Nikolopoulos (1969). Our measurements show that the three specimens in the type series vary in size from 2.5–2.8 mm, thus falling within the size range of R. diaboli .

In the same sex, the shape of the pronotum does not vary significantly between both species. As previously mentioned, the microreticulation of the pronotum of R. diaboli is highly variable ( Figs. 8, 9 ), including totally smooth forms like those observed in type specimens of R. atticus ( Fig. 7 ).

Considering genitalia, the shape of the median lobe in profile, and the arrangement of setae on it, are perfectly similar between specimens of R. diaboli ( Fig. 18 ) and the holotype of R. atticus ( Fig. 17 ). We do not find the differences in the schemes presented by Dodelin (2021). The genitalia’s internal features of R. atticus holotype are not fully visible, because the genitalia are old and dried out ( Fig. 14 ). Only a chemical treatment would possibly allow us to observe the genitalia in their entirety, but this method has been ruled out to avoid any damage. Nevertheless, the broad, rectilinear medial sclerite and the partially visible anterior sclerite are like those observed in R. diaboli ( Fig. 15 ).

As a conclusion, considering the similarity in morphology and genitalia, as well as the lack of consistently differing characters between the two species, the following synonymy is established:

Figures

FIGURES 5–13. Figures 5–6. Habitus—5. R. atticus from France, ♀, 3.0 mm. 6. R. depressus from France, ♀, 3.6 mm. Figures 7–10. Pronotum—7. R. atticus, holotype ♂. 8. R. atticus, shiny form, from France, ♂. 9. R. atticus, microreticulate form, from France, ♀. 10. R. depressus, from France, ♀. Figures 11–13. Antennal club—11. R. atticus, holotype ♂. 12. R. atticus, from France. 13. R. depressus, from France. (Photos: Alexis Vincent).

FIGURES 14–19. Figures 14–16. Median lobe of aedeagus with internal sclerites (dorsal view)—14. R. atticus, holotype ♂. 15. R. atticus, from France. 16. R. depressus, from France. (Photos:Alexis Vincent). Figures 17–19. Median lobe of aedeagus (lateral view)—17. R. atticus, holotype ♂. 18. R. atticus, from France. 19. R. depressus, from France. (Photos: Alexis Vincent).