The tiny gnat-sized fly found on a trickling filter is called the _____ fly.

The tiny gnat-sized fly found on a trickling filter is called the _____ fly.

• A. Culex
• B. Simulium
• C. Psychoda
• D. Anopheles

Answer: (C)

Drain flies, also called sewer or moth flies, are the small insects commonly seen around trickling filters in wastewater plants. They belong to the genus Psychoda. Their larvae develop in moist, organic-rich films on surfaces, so a trickling filter provides the perfect habitat for them to grow. Adults are tiny, only a few millimeters, with hairy, moth-like wings held over the body. That combination—tiny size, moth-like hairy wings, and association with moist organic matter in wastewater—points to Psychoda as the fly on the trickling filter. This is distinct from mosquitoes such as Culex or Anopheles, which have different breeding habitats and appearances, and from blackflies of genus Simulium, which are not typically found massing on trickling filters.

Drain flies, also called sewer or moth flies, are the small insects commonly seen around trickling filters in wastewater plants. They belong to the genus Psychoda. Their larvae develop in moist, organic-rich films on surfaces, so a trickling filter provides the perfect habitat for them to grow. Adults are tiny, only a few millimeters, with hairy, moth-like wings held over the body. That combination—tiny size, moth-like hairy wings, and association with moist organic matter in wastewater—points to Psychoda as the fly on the trickling filter.

This is distinct from mosquitoes such as Culex or Anopheles, which have different breeding habitats and appearances, and from blackflies of genus Simulium, which are not typically found massing on trickling filters.