The Tasar silkworm Antheraea mylitta D. is reported to be attacked by a host of pests. These pests are broadly categorized as predators and parasitoids. Predators cause damage to Tasar larvae during early instar and parasitoids during late stages to Tasar silkworm larvae. Apart from these pests, of late infestation of the dermestid beetle, Dermestes ater was observed in Tasar sericulture. During the first and second crop grainage season of 2013, the infestation of D. ater was noticed in the grainage house of Silkworm Breeding and Genetics section of CTR&TI, Ranchi. Both the grubs and adults were found feeding on the pupa and ovipositing moth. The infestation was observed in the open cocoon, ovipositing female moths inside the paper oviposition box, dead moths in the grainage house, and in the debris of the grainage house. The incubation period of eggs was 7.33 days. Developmental duration of grubs lasted for 102 days. Pupal duration was 7.33 days. The adults and grubs of Dermestes ater were observed to feed on pupa, moth and silk fiber and cocoon shell of Antheraea mylitta. Further, detailed studies are required on the feeding behavior, habit and habitat, and extent of damage caused by these beetles in Tasar sericulture.