We conducted a rearing experiment with the chironomid species Chironomus riparius to assess the relationship between the δ13C values of chironomid larvae and the δ13C values of their exuvial head capsules. Our experiment was also designed to study the extent of the trophic fractionation factor (Δ13C) under different dietary conditions. Three food sources were used (Tetramin, oats and corn), covering a range in δ13C values of 14.55 ‰. For each of the four successive instars, carbon isotope ratios were measured in larval tissues and head capsules. This approach highlighted the variability in δ13C for both larvae and their head capsules during larval development. Once the larvae reached the 3rd instar, their δ13C values were stabilised and did not significantly differ from their food δ13C (Δ13C = 0 ‰). It is probable that the variability in the δ13C offset during larval development reflected a difference in the carbon turnover for the chironomid cuticle compared with the whole body. At the 4th instar, the δ13C offset did not significantly differ between the three food sources and was −0.9 ± 0.2 ‰. The proposed Δ13C and δ13C offset values can be considered as a first step for the reconstructions of the chironomid larvae paleo-diets with the aim of deciphering the different organic carbon sources supporting chironomid larvae productions. However, the influence of the environment (e.g. temperature, oxygen), other food sources (e.g. different nutritive values) as well as taxonomy (i.e. other chironomid species) should be assessed to strengthen the robustness of these results.