We have launched a new citizen science project called “Okáčům na stopě”, which aims to involve the broad public in the study of the population ecology of the critically endangered Hipparchia semele butterfly in the Prokop Valley and its surroundings. In the past, the rock grayling (Hipparchia semele) was one of the most widespread large Satyrid butterflies in the Czech Republic, but today it is one of the most critically endangered species. The general public can help us by taking pictures of butterflies, preferably those with codes on the wings, using the iNaturalist application (https://www.inaturalist.org/projects/okacum-na-stope). You can follow the news about the project on our Facebook (https://1url.cz/@FBokacumnastope) or occasionally on TV (https://www.ceskatelevize.cz/porady/1097181328-udalosti/221411000100801/video/855377).