Products made of plastic have revolutionized people's way of life worldwide since they first appeared in 1950. Plastic products have many benefits to our society, but they have also provoked severe environmental problems and caused issues for many organisms. Microplastics (particles between 1 and 5000 micrometers) have a negative impact on many biological processes, including the development, immune system, and stress levels of different organisms. In the present study we report, for the first time, a kind of mechanical damage caused by microplastics to a greater wax moth larva Galleria mellonella (Lepidoptera, Pyralidae). This damage involved an interference in their cuticle development, provoking its death. Damage to development-related structures represents an acute lethal factor. Since an increasing number of insects are in contact with this pollutant in nature (e.g., soils), this type of damage becomes relevant and deserves attention from the scientific community.