Updated project metadata. The midgut of the tick is the most important tissue for the storage and digestion of host blood, which serves as the sole source of energy and nutrients for all tick development and reproduction. During feeding at each developmental stage, dynamic changes in the tick midgut epithelium reflect changes in physiological processes in this tissue. In addition, the midgut serves as the primary interface between the tick and tick-borne pathogens, which determines the vector competence of the tick. Several transcriptome data from Ixodes ricinus have been published, but few studies have examined tick proteomes. In contrast to transcriptome data, proteomics provides a deeper understanding of key cellular processes occurring in the investigated tissues. In this work, we present for the first time insight into proteomics of the midgut of I. ricinus nymph. Label-free quantitative proteomics was used to elucidate changes during blood meal and development in I. ricinus. A total of 1 534 I. ricinus-specific proteins were identified, with only a few host proteins detected. In addition, the proteins involved in the specific physiological processes of the tick were studied in detail to gain better insight into the ontogeny of the midgut of the nymph.