The hard nucleus between silkworm chrysalis embryo and nerve bundle is silkworm chrysalis embryo and nerve bundle. Specifically: embryo: the black nucleus in the middle of silkworm chrysalis is the embryo of silkworm baby, which is wrapped inside and has not been exposed to harmful substances. Nerve bundle: the black core between cocoon and pupa is also the nerve bundle of silkworm pupa, which hatches and develops into the nervous system of silkworm. Edible safety: Although the hard core in the middle of silkworm chrysalis is edible, people with allergic constitution may have allergic reactions due to its high protein content. Therefore, if people feel uncomfortable or allergic when eating the black core of cocoon and pupa, they can remove the black core before eating. To sum up, the hard core in the middle of cocoon and pupa is edible, but attention should be paid to food safety and personal physique differences.