Beautiful photos of various insects, and I appreciate that you try to provide their scientific names (it's ok only to name the insect family instead of the exact species).
PEST OR USEFUL FOR HUMANS
Well, some fly species partly stay at dirty places and thus can pass diseases on to people. However, the dirt itself is most of the time created by us humans ...
As insect lover I sometimes like to change perspective and if someone asks me if this or that animal is a pest or 'useful' for us, I ask back if actually Homo sapiens is a pest (destroying the forest, polluting the air, litter plastic in the environment and the oceans, leading wars, producing nuclear waste) or useful for the planet? Well, I can understand that most humans don't really like these kind of questions ...
RE: PEST OR USEFUL FOR HUMANS