Larva, prepupa (last instar larva), pupa, and an empty shell of pupa after hatching of the black soldier fly Hermetia illucens contain eumelanin, an active synthesis of which is observed at the prepupal stage, which is probably due to the release of prepupa from the feed substrate thickness to the open space for pupation. It was shown for the first time that prepupa contains high quantities of the magnetically active form of manganese Mn2+. This fact indicates that Mn2+ stimulates the copper-containing tyrosinase-the key enzyme in the synthesis of melanin in the period of migration and adaptation of the insect to the solar radiation.