Dans la nuit, après mon message précédent + quelques recherches sans succès chez les Bethylidés, j'ai envoyé un courriel à Jeroen de Rond, qui nous avait bien renseignés sur mon premier spécimen dans cette famille (
Sclerodermus ephippius).
Sa réponse, assez longue, vient de me parvenir et, suite à une tentative assez décevante de traduction en ligne, je ne peux que vous livrer la version anglaise, en demandant à une âme charitable de bien vouloir traduire ; je pense toutefois avoir compris qu'il s'agirait d'une femelle de
Bethylus dendrophilus, espèce et genre pas encore en galerie :
your specimen is obviously a Bethylus female. Bethylinae are easily recognised by the convexly arched clypeal carina, running higher than in other subfamilies and reaching the vertex behind the antennal sockets. The stigma in the forewing is usually quite large and the radial vein ends in a hook.
After enhancing your photographs (the lower are quite dark) I noticed erect light hairs on the hind edge of the head. I think that the eyes are glabrous, and not haired like in Bethylus (Anoxus) boops. So, that leaves only Bethylus dendrophilus, a species that is relatively unknown, but in fact will not be uncommon in Western Europe. It lives in trees, that much is known, but nothing has been published about its hosts. Possible candidates could be Psychidae, of which the larvae build Trichoptera-like casings of all kinds of collected material.
I got many specimens of Bethylus dendrophilus from a scientific team, running an experimental orchard in The Netherlands. Most of the females have been collected in summer, but they can already be found in early spring. The fact that you encountered this female in winter is no exception: all Bethylus females hibernate.
If you see these wasps running over the leaves of plants or trees in your garden you might discover what they are interested in. That would probably reveal new evidence. Rearing the larvae that they place on a caterpillar would offer enough material for a scientific article.
The females are fast runners and hardly ever fly. I observed many females of Bethylus cephalotes and Bethylus fuscicornis running over the leaves of tussilago in wet sandy environments during the summer. Males of most species have rarely been collected. They either are extremely rare or emerge only for a few days.
Au cours de mes recherches, j'ai noté une ressemblance certaine avec des photos de la galerie classées dans les inconnus de la famille (
cf. 82037 et
103131) ; si vous trouvez ça pertinent, ça pourrait faire avancer leur détermination, au moins jusqu'au genre.
... Pierre.
