Insect decline necessitates the development and use of standardized protocols for regular monitoring. These methods have to be rapid, efficient, and cost-effective to allow for large-scale implementation. Many insect sampling and molecular methods have been developed. This includes Malaise trapping, high-throughput DNA barcoding (“megabarcoding”), and metabarcoding. The latter allows for assessing the species diversity in whole samples using few steps, but sample heterogeneity in terms of body size remains a challenge since large insects contribute disproportionately more mtDNA than small ones, potentially overwhelming the template DNA from small species that then go undetected. Size-sorting can mitigate this problem, but no satisfying automated, rapid and non-destructive solutions are available. We introduce the EntoSieve, a low-cost and DIY motorized instrument that disentangles and sorts abundant insect bulk samples into several body-size fractions while minimizing damage to specimens thus reducing the risk of DNA contamination across size fractions (e.g., legs of large specimens in small body-size fraction). EntoSieve utilizes readily available components, 3D-printed parts and customizable meshes, thus enabling parallelization at low cost. We here show the efficiency of the EntoSieve for three samples with more than 10,000 specimens using three sieving protocols and assess the impact on specimen integrity. Efficiency ranged from 92-99% and achieved within 18-60 minutes and specimen damage was not significant for subsamples. By facilitating rapid pre-processing, the device contributes to producing morphologically valuable vouchers for megabarcoding and is likely to improve compositional diversity accuracy across size classes when using metabarcoding.

Understanding and combatting biodiversity loss are critical tasks facing our planet. They are made especially difficult because much of the earth’s biodiversity is concentrated in abundant and speciesrich groups of invertebrates like insects. Traditionally, samples of insects have been analyzed manually by experts using morphology. Not only does this necessitate taxonomic expertise, but it is also error-prone, time-consuming, and often involves commercial microscopes that are too expensive for many countries in the Global South where most species are found. The alternative to expert sorting with morphology is the use of DNA barcoding. However, this requires a well-equipped laboratory and an entirely different skill set. We present an alternative solution: a low-cost, open-source photomicroscope for taking high-resolution, focus-stacked images that can be used for insect classification: the Entomoscope. We describe two different versions of the Entomoscope, a standalone version that can be operated without additional hardware and an even simpler Version, that requires a computer. We show that the optics are of sufficiently high quality to classify specimens with >95% accuracy into 15 different types of insects (mostly ’families’ according to the Linnean classification). The classifier can be successively extended or individually trained for specific classification tasks. Here, we provide building instructions, 3D files, and a list of commercially available parts so that everyone can build their own Entomoscope. Open-source DIY hardware like the Entomoscope facilitates affordable, cutting-edge biodiversity research by entomologists around the globe.