## 1 Introduction  
Scientific research on insects is usually supported by a variety of techniques, which allow the gaining of knowledge on their morphology and anatomy [1]. Main morphological methods, such as photomicrography [2] and scanning electron microscopy (SEM) [3], aim at analyzing the cuticular structure and body surface of insects. In addition, anatomical studies often include one or more following approaches: histology [4; 5; 6], confocal scanner laser microscopy (CLSM) [7], light-sheet fluorescence microscopy (LSFM) [8], serial block-facescanning electron microscopy (SBSFM) [9], dual-beam scanning electron microscopy (FIB-SEM) [10; 11; 12; 13], nuclear magnetic resonance imaging (NMR) [14; 15], and micro-computed tomography (micro-CT) [16; 17; 18].  
All these techniques have advantages and disadvantages and require specimen preparation before they can be performed. This, however, often makes it difficult to use a certain sample for other types of analysis, with different techniques and instruments. For example, a paraffin-embedded sample prepared for histological analysis may not be usable for subsequent electron microscopy. On the contrary, a sample embedded in the resin may be utilized for both electron microscopy and histology, if the resin sections are colored with, for instance, methylene blue or toluidine blue. Moreover, the scarcity of insects to be used may determine strong limitations regarding the technique to be chosen. In fact, it is not always possible to have many samples of a certain species and if destructive analyses were to be performed, for example by embedding, sputter-coating, or preparing them for histology, this would make it impossible to use the same samples for further studies using different techniques. Some specimens may come from old museum collections and be holotypes of a certain species, prohibiting the use of analyses schemes that would damage the specimens.  
In order to study a certain rare sample or one that is difficult to collect in nature, one of the most versatile techniques remains scanning by micro-CT/synchrotron radiation (SR) micro-CT [19]. This is because micro-computed tomography is a non-destructive and very rapid (at least when compared to histology) three-dimensional imaging process, which results in virtual slices of even very small samples at high resolution [20], providing a high level of detail of both internal and external features. Another advantage of this technique is that specimens which had been previously prepared for TEM, SEM, or other kinds of investigations may still be able to be scanned. micro-CT is frequently used even when dealing with amber fossils [21; 22; 23], another type of specimen that is rare and hardly available in large numbers. If the number of samples available for a study is sufficient, and the species themselves are not extremely rare to find, the quality of the micro-CT scans can be improved by applying dedicated sample preparation steps, such as chemical or freeze-drying and/or heavy metal-based stainings. Usually, these tissue stainings lead to an improved image contrast, especially for soft-tissue components [24; 25; 26]. Some of the more common examples of stains are iodine, PTA, and silver staining. micro-CT is also useful for live imaging of whole invertebrates, for example by using carbon dioxide as an anesthetic and preventing animal movement during scanning [27].  
In this work, specimens of the Diptera, Hymenoptera and Coleoptera insect orders were scanned via both micro-CT and SR-micro-CT, using four of the most frequently utilized types of sample preparation for morphological studies to improve the ability for the rendering of 3D models and evaluate the pros and cons of using samples for 3D reconstruction, that had not previously been prepared for micro-CT.