Fatty acids as components of cuticular lipids of insects play a significant role in antifungal in protection against fungal infection. The chemical composition of cuticular and internal extracts obtained from all developmental stages of flesh flies Sarcophaga carnaria was identified. The fatty acids were detected using gas chromatography coupled with mass spectrometry and the most abundant for all examined stages were: 18:1 > 16:0 > 16:1 > 18:0 > 18:2. Polyunsaturated fatty acids (PUFA) C20 were found in both, cuticular and internal extracts. GC–MS analysis showed higher relative content of PUFA in adults than in preimaginal stages.

Fatty acids alone as well as their cuticular and internal extracts obtained from larvae, pupae male and female of S. carnaria were tested according to their potential antimicrobial activity against entomopathogenic fungi: Paecilomyces lilacinus, Paecilomyces fumosoroseus, Lecanicillium lecanii, Metarhizium anisopliae, Beauveria bassiana (Tve-N39) and B. bassiana (Dv-1/07). FA presented diverse antimicrobial activity depending on the length of the chain and the presence of unsaturated bonds. Short chain and unsaturated FA (6:0, 11:0, 13:0) have shown significantly stronger activity against fungi but they were detected in lower concentrations. PUFA inhibit fungal growth more effectively than unsaturated long chain fatty acids. Cuticular and internal extracts of all living forms of S. carnaria exhibited approximately equal activity against tested entomopathogenic fungi. We presumed that the most abundant saturated long chain FA and additionally PUFA founded in our analysis are involved in protecting the flies against fungal infection.