Of the Hundreds of thousands of plant species in the world, silkworms (Bombyx mori) consume only one species, the white mulberry (Morus alba L.). This narrow specificity is still poorly understood. In this study, we compared the chemical composition of white mulberry (Morus alba L.) leaves with that of black mulberry (Morus nigra L.), used as a control. We analyzed the quantity of polyphenols, essential oils, proteins, and other substances present. The results revealed significant differences between the chemical composition of the leaf extracts from the two trees. The results of our research revealed that the yield of essential oils present in the leaves of Morus nigra (0.54%) was higher than that of the leaves of the host plant Morus alba (0.21%). The dosage of polyphenols contents showed a 72% superior value in Morus nigra leaf extracts compared to Morus alba leaf extract. In line with our results, studies have shown that high concentrations of essential oils and polyphenols present in plants play a repellent role for silkworms (Bombyx mori).  The results also showed that the dosage of total chlorophyll and proteins was higher in Morus alba leaf extracts compared to Morus nigra (43% and 28% respectively). The final result was electrophoresis, which showed the presence of certain silk proteins in the leaves of Morus alba and not in those of Morus nigra, to explain the specific preferences of the silkworm. Other parameters, such as carotenoids and soluble sugars did not show any significant difference between the leaves of the two species. Thus, it appears that the silkworms are not attracted by a single molecule or substance, but rather by a structured arrangement of several substances, each playing a role in this close relationship between the white mulberry (Morus alba L.) and the silkworms (Bombyx Mori).