There are many biological factors that influence the developmental stability and therewith the morphological symmetry of species, such as the environment, stress during development, hybridisation between species, inbreeding and loss of genetic variability. Here, we analysed the developmental stability of wing traits of the butterfly Parnassius apollo, a threatened species with small local populations. We assessed the historical trajectory of developmental stability as measured by fluctuating asymmetry (FA) to evaluate the effect of protection and management actions on an Apollo population in Germany. We analysed 89 individuals collected from 1906 to 2004 at six morphological wing traits, four of which were FA traits. Our results show that legal protection (= listed on a red list) alone did not have any effect on FA and hence did not improve the population fitness. However, FA showed a clear response to management actions, but only after several generations. In 2004, 13 years after population management actions were implemented, the variance of population wide FA was comparable to the FA-variance from the beginning of the 20^th century. Our study supports the utilisation of FA as an assessment tool of effects of population management.