## 5 Conclusions  
Scanning techniques using micro-CT have now become increasingly common over the past 20 years, starting with primarily medical applications [36], and then extending into paleontology [34], the geosciences [37], and finally into entomology [26; 38; 39].  
This has allowed samples from different sources to be used and further exploited, from a morphological/functional/evolutionary perspective [40; 41].  
With this work, we wanted to demonstrate the power of this technique, using samples of very rare insects and difficult to find (in nature or museums), prepared in different ways. We can resume our findings in the following points:  
* 3D models will have the best details, especially for the interior organs when the samples are scanned with an SR-micro-CT, thanks to the higher resolution it can achieve, despite its higher pixel size value.
* When possible, it would be best to specifically prepare the samples for micro-CT (for example, with the staining methods reported in [25]).
* If the interest is mainly on the external surface of a specimen, even an old museum sample can be used (after the removal of dust on its cuticle).
* When is important to visualize and segment internal organs and structures, critical-point dried specimens produce the best results.
* The removal of the glue and cardboard in museum specimens, if possible, will yield better results in the final 3D model, and eliminate a lot of work to digitally remove those parts in the mesh.
* Finally, samples specifically prepared for Electron Microscopy (as in sputter-coated) will present a lot of artifacts in the final model, rendering them not easily usable.  
Our resulting 3D models can and will be used in the future for new interesting morphological analyses, and will guide additional histological and electron microscopy studies.  
Conceptualization, F.S.M., M.M., F.S. and A.D.G.; methodology, F.S.M., G.T., C.D., M.M. and A.D.G.; software, F.S.M., M.M., F.S., G.T. and C.D.; investigation, F.S.M., M.M. and A.D.G.; resources, A.D.G.; data curation, F.S.M., M.M. and A.D.G.; writing--original draft preparation, F.S.M.; writing--review and editing, F.S.M., M.M., F.S., G.T., C.D. and A.D.G.; visualization, F.S.M. and M.M.; supervision, F.S.M., M.M., F.S. and A.D.G.; project administration, A.D.G.; funding acquisition, M.M., G.T. and A.D.G. All authors have read and agreed to the published version of the manuscript.  
This research was founded by the SYNTHESYS project (Synthesis of systematic resources, the European Union-funded Integrated Activity Grant), grant number DE-TAF-5591; ELETTRA SYRMEP (SYrchrotron Radiation for MEdical Physics) beamline, proposal number 20160088; DI-PARTIMENTO DI ECCELLENZA (Grant of Excellence Departments, MIUR Italy, L232/2016-Art. 1, comm 314-337) awarded to the Dept. of Science, University of Roma Tre, Rome, Italy 2018/2022.  
Not applicable.  
Data Availability Statement: Data available on request.  
We would like to thank [PERSON] for providing us with some paussing samples used for this work; and [PERSON], for sampling _Microdon_ specimens that have later been scanned for this study. We are also particularly grateful to [PERSON], [PERSON], and [PERSON] for the help given during the acquisition of the data at the Museum fur Naturkunde. Finally, we are deeply in debt with our friend, [PERSON], for his invaluable tips during the various steps for the creation of this manuscript.  
The authors declare no conflict of interest.