Final answer:
The visible signs of an active bed bug infestation are mosquito-like welts, a 'musky' smell, small blood stains on sheets, and tiny, sand-sized black pellets.
Step-by-step explanation:
The visible signs of an active bed bug infestation can include mosquito-like welts, a 'musky' smell, small blood stains on sheets, and tiny, sand-sized black pellets. Bed bug bites can often resemble mosquito or flea bites and can cause itchy welts on the skin. If you notice multiple bites in a line or cluster, it could be a sign of a bed bug infestation.
Bed bugs can also emit a distinct odor described as 'musky' or 'sweet.' This odor is caused by the chemicals released by bed bugs in their pheromones. Small blood stains on sheets or pillowcases can be caused by bed bugs being crushed during feeding. Additionally, bed bug infestations can leave behind tiny, sand-sized black pellets known as bed bug feces. These pellets are often found in mattress seams, furniture cracks, and other hiding places.