This is called the Oniscidae. You may find them under a brick or a damp object. You may have felt disgusted and wondered  why they exist in nature.  Well, let me tell you, the  oniscidae , better known as cochineal, is a subgroup of isopod crustaceans  whose function is to remove harmful heavy metals  from the earth such as mercury, cadmium and lead. They contribute to the cleansing of soil and groundwater to reaffirm  the wisdom of nature. Do not damage them or spray pesticides!