When it comes to detecting roaches, all of the senses may have their turn at indicating a cockroach presence. The most common signs are the things that may be seen, but smells and sounds could be factors to consider as well.
Cockroaches tend to scurry quickly out of sight but there are a few different stages of a roach that you could see moving around in your kitchen, bathroom, or yard depending on what species it is.
Adult cockroaches will vary in color from species to species, but they are an elongated oval shape with long, curling antennae, cerci on the back of the abdomen, and wings that cover most or the entire abdomen. They are most comfortable in tight spaces with pressure on 3 sides of their body, but they will travel out where they can be seen when looking for food or pushed out by population pressures.
The adolescent cockroach is distinct from the adult in appearance mostly due to the lack of wings, but their body shape changes as well as it develops. The nymph stage of the cockroach will be found in the same places as the adults typically.
Cockroach egg capsules are joined together in an Ootheca. Some species of roches will carry them on their abodumen, but others will deposit them in cracks, crevices, and holes where the eggs and hatchlings will have protection. In some cases, they can be found on the underside of cabinetry, in the corner behind appliances, or other similar places.
Roaches love to eat and squeeze in and out of tight places which results in visible fecal droppings where they traffic. These droppings are small brown or black flecks that may appear like pepper flakes or may be large enough to look like small mouse droppings.
As cockroach nymphs develop, they will molt and leave behind a shed skin called anexuviae. Seeing shed roach skins may indicate that a population is developing, but it could simply be left over remnants from a previous roach population.
If you are checking out a new home or business and see roach bait stations, you can assume that there has at least been a concern of cockroaches and should investigate further.
Roaches are small and like to stay out of sight. They can move quickly if they think they are about to be exposed. Oftentimes, some of the first signs of the presence of a cockroach population is the slight sound of scurrying tiny legs as they scatter when a light is turned on in the kitchen, a cupboard door is open, or simply when a sound disturbs their rest back in a wall void. It would be difficult to identify them off of sound alone, but a scurrying as described above would be an indication that further investigation should occur.
The larger the population, the more distinct the smell will be, but those that are experienced with recognizing the musty, oily odor of roaches may be able to pick up the scent with just a few roaches. Some of the smell is related to the environment which they foster, but some of it comes directly from them and their feces left behind.
If you are unsure of a roach presence, but would like to confirm, glue boards can be a wonderful tool. Simple place them in areas of highest suspicion and check them for adults or nymphs that attempt to scramble across. If you are unsure of where to begin placing them, dark, warm, tight spaces such as between fridges, ranges, and cabinetry are great starting points.