tokens: of luminosities for the LMC reported in Table 1 . Concerning the mass-loss rates, Riebel et al. ( 2012 ) find that the C-stars in the LMC with the highest degree of obscuration are injecting into the interstellar medium carbonaceous dust with a rate of ∼10 −7 M ⊙ yr −1 . This is translated into an overall mass-loss rate of ∼2 × 10 −5 M ⊙ yr −1 . 2 This quantity is significantly smaller than the result reported in Table 1 , which is in much better agreement with the results published by Gullieuszik et al. ( 2012 ), van Loon ( 2006 ) and Groenewegen et al. ( 2007 ). On the chemical side, we have seen that the conclusions we may draw for the SMC and LMC are different. In the former case, we showed that within the context of our description of the AGB and dust systems, the colours of the C-stars exhibiting the highest degree of obscuration are reproduced only if the amount of carbon accumulated at the surface exceeds ∼0.5 per cent of the total mass. This C abundance corresponds to a C/O ratio above 3. The IR colours of the most obscured LMC C-stars are however less sensitive to the surface carbon abundance than their SMC counterparts. The uncertainties affecting the degree of carbon enrichment are still significant, which is confirmed by the differences between the monash (surface carbon mass fraction slightly below 0.02, C/O ∼ 10) and aton ( X (C) ∼ 0.01, C/O ∼ 3) models. The most obscured C-stars in the MCs are very faint in the optical domain but much brighter in the near-IR. Thus, the best observational way to test the different nature (i.e. progenitor masses) of the obscured C-stars in the SMC and LMC would be to obtain follow-up high-resolution () near-IR ( JHK bands) spectroscopy of these stars. This can be done with actual instrumentation (e.g. CRIRES at European Southern Observatory/VLT). From such spectra, one could get the CNO elemental abundances, which are expected to be different in both types of stars (see e.g. Ventura et al. 2015b ). On the other hand, an analysis of the chemical composition of planetary nebulae (PNe) in the MCs would provide important complementary information on the chemical enrichment of C-stars in these galaxies. This is because only small surface abundance changes are expected from the final AGB phase to the PN stage. For example, Ventura et al. ( 2015b ) showed that the most C-enriched PNe in the LMC display carbon abundances below X (C) ∼ 0.01, in agreement with the 2.5 and 3 M ⊙ aton models and with the 2.25 M ⊙ monash model (see the bottom-right panel in Fig. 1 ). The extension of this type of analysis to a much wider sample of PNe in the LMC (and also to the SMC PNe) will help us to understand whether this upper limit in the carbon abundance is real, or due to the limited sample of PNe examined. 7 CONCLUSIONS We use Spitzer IR data of C-stars in the MCs to improve our understanding of the evolution of AGB stars with masses below ∼3 M ⊙ , which become carbon stars through repeated TDU events. We focus on
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