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The eggs of the Mediterranean flour moth, <i>Ephestia kuehniella</i>, are frequently utilized as alternative diets and have demonstrated promising outcomes when consumed by various insects. Nonetheless, the specific reasons for their effectiveness remain unclear. In our study, we assessed the developmental performance of the ladybird <i>Propylea japonica</i> when fed <i>E. kuehniella</i> eggs, alongside 12 factitious prey or artificial diets. Our findings revealed that ladybirds fed <i>E. kuehniella</i> eggs displayed a performance comparable to those fed the natural prey <i>Megoura crassicauda</i>. Transcriptome profiling of larvae raised on <i>E. kuehniella</i> eggs and <i>M. crassicauda</i> revealed that genes upregulated in the former group were enriched in metabolic pathways associated with carbohydrates, lipids, and other essential nutrients. This suggests that <i>E. kuehniella</i> eggs may have a higher nutrient content compared to natural prey. Furthermore, a notable downregulation in the expression of immune effector genes, such as <i>Attacin</i> and <i>Coleoptericin</i>, was observed, which might be attributed to the lower microbial content in <i>E. kuehniella</i> eggs compared to <i>M. crassicauda</i>. We suggest that the difference between <i>E. kuehniella</i> eggs and <i>M. crassicauda</i> as food sources for <i>P. japonica</i> lies in their nutrient and microbial contents. These findings provide valuable insights for the advancement of innovative artificial breeding systems for natural enemies.