Which of the following flies are known to cause issues by entering homes?

Drain flies are known to cause issues by entering homes due to their breeding habits and attraction to moisture sources. They often reproduce in wet, organic matter, such as decaying leaves or sludge found in drains, which allows them to thrive in indoor environments. Their presence can indicate issues related to hygiene and sanitation, as they can lead to unpleasant odors and potential contamination of food sources.

Other types of flies, while they may enter homes, typically have different behaviors or ecological niches. Biting midges are more associated with outdoor environments and are known for their painful bites, rather than entering homes. Flesh flies generally lay their eggs on decaying organic material outside rather than indoors and are more commonly encountered around areas where animal carcasses or waste are present. Stable flies, similarly, prefer to remain near livestock and outdoor environments rather than actively seeking entry into human residences. Thus, drain flies stand out as the ones specifically linked with indoor issues.