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Hi Theo Zeegers,
Thank you very much for your expert suggestion! Thanks to your input, I have come to the conclusion that this is a Masistylum arcuatum. The genus description provided by Pierfilippo Cerretti matches perfectly, at least for all the parts visible in my photos.Furthermore, in Pachystylum the post-sutural dc setae are generally 4 (my specimen has 3), and the median marginal depression on syntergite 1+2 extends all the way to its posterior margin (whereas in my specimen it stops halfway).
Thank you so much for your help!