What may be nearby if you are finding high infestations of moth flies?

Finding high infestations of moth flies typically indicates the presence of moist and decaying organic material, which is favorable for their breeding. Moth flies, also known as drain flies or sewage flies, thrive in environments where stagnant water or organic waste is present, making them commonly found near sewage treatment plants. These facilities often create conditions where organic matter accumulates, providing an ideal habitat for moth flies to reproduce.

Conversely, while locations like sausage plants, sand or gravel pits, and meat packing plants can attract various pests due to their operations, they do not generally create the same moist, organic conditions that moth flies prefer. Sausage plants may have some waste, but they typically do not maintain the high moisture levels ideal for moth fly infestations. A sand or gravel pit would lack the necessary organic matter altogether, and although a meat packing plant could attract flies due to the presence of animal products, it does not mimic the specific environment created by sewage treatment plants. Thus, the strong association of moth flies with sewage and organic waste makes the sewage treatment plant the most relevant answer.