How can the presence of cockroaches be determined?

The presence of cockroaches can be effectively determined by locating cast skins and droppings. Cockroaches undergo a process called molting, where they shed their skin as they grow. These cast skins are a clear indicator of their presence in an area. Additionally, cockroach droppings, which resemble small black specks or coffee grounds, are another physical sign of an infestation. The combination of these two factors can provide strong evidence of cockroach activity.

While other options might provide some indications, they are not as definitive or practical for confirming an infestation. For example, observing movement may require prolonged surveillance and might not yield conclusive results since cockroaches can be elusive. Smelling their pheromones is less reliable for the average person since pheromones are often not detectable without specific training or equipment. Monitoring bait traps can help confirm the presence of cockroaches once they are attracted and caught but does not directly indicate the full extent of an infestation like cast skins and droppings do. Therefore, locating cast skins and droppings is the most thorough method for determining the presence of cockroaches.