Cockroaches grow to 1.5 – 2 inches. Many assume they need a crevice of up to 2 inches in diameter to crawl through. However, roaches can fit through much smaller holes.
Cockroaches can fit through one-tenth-of-an-inch crevices. They do this by flattening their body to about a fifth of its normal height. Roaches squeeze through such tight spaces slowly. But they can also run rapidly through small spaces when they only flatten their body to half its normal height.
Cockroaches and their ability to crawl through what seems like a space that’s too tight have been studied by scientists. It turns out roaches adapt by flattening their bodies to get through a tight space.
How small is a small space for cockroaches?
Cockroaches have been shown to squeeze through crawl spaces as tight as 0.10 inches. All cockroaches (regardless of their size) in the US can crawl through such small spaces regardless of their size. The common US roaches have the following sizes.
American cockroach – up to 3 inches
German cockroach – up to 0.63 inches
Oriental cockroach – 1 inch
Brown-banded cockroach – up to 1.2 inches
Smoky brown cockroach – up to 1.49 inches
American cockroaches have the most difficult time making it through tight spaces as they are the largest.
Most American cockroaches have an average size of 1.6 inches but they can be as large as 3 inches. These roaches are also 0.28 inches tall on average. These bugs flatten their body so that the height is lower than 0.14 inches when going through tight spaces smaller than their normal body size.
Why can cockroaches squeeze through small spaces?
Cockroaches squeeze through many spaces such as wall cracks or the space under doors. These insects have been known to make it into the house even through the smallest spaces.
Roaches never make it through tight spaces with their regular body posture as they need to adapt. Similar to animals that make it through tight spaces, cockroaches take a few measures that allow them to successfully move through very small spaces.
Cockroaches flatten their body
Cockroaches show adaptability when trying to squeeze through small spaces by flattening their body. Each different species of cockroaches can do this to a different extent.
Studies show cockroaches can flatten their flexible exoskeletons. The extent to which this flattening happens determines if they can squeeze through a small space or if they can continue running at high speed.
One-fifth is the maximum extent to which the height of cockroaches can be flattened. This maximum extent doesn’t allow them to run but rather squeeze through small openings or crawl spaces smaller than an inch.
Roaches splay their legs to the side
Cockroaches are known to splay their legs to the sides to flatten their bodies. This would make it seem they would not be able to move their bodies.
Tibias are used for cockroaches to move whenever their legs are splayed to the sides. This segment of the legs is used to push against the floor or nearby walls so that roaches make it through some of the smallest spaces.
Cockroaches can run through small spaces
Speed is one of the most impressive characteristics of roach movements. These small insects can move at high speed even when flattening their bodies.
Running from a perceived risk such as people or rain makes roaches move through tight spaces at high speed. This is when they only flatten their bodies up to half their normal height.
This means the American cockroach can squeeze through tight spaces while running if these spaces are up to 0.14 inches tall. Spaces underneath doors that measure at least 0.14 inches freely allow cockroaches to crawl through at high speed.
The extreme limits of tight spaces and roaches squeezing through
Lab studies show the extreme limits of spaces cockroaches can crawl through.
It turns out cockroaches can crawl through small spaces that are only 3mm (0.11 inches) tall. This is achieved through an extreme body flattening where the legs are splayed to the sides.
These are the smallest spaces cockroaches can squeeze through using dragging movements implemented with the tibia section of the legs.
3 Common reasons why cockroaches like to squeeze through small spaces
It may seem like cockroaches are putting in a considerable effort to crawl to tight spaces. This isn’t the case as they like to crawl through these spaces for the following reasons.
1. To move from one place to another
The most common reason cockroaches make their way through small openings where they have to squeeze their bodies is to move around. They do this when moving from one room to another or when seeking out food that’s hard to reach.
Food traces behind the furniture or under the fridge are very appealing to roaches which go to extreme lengths to get to them.
2. To escape predators
Cockroaches know squeezing through tight spaces saves them from common predators. This includes mice and shrews.
Other roach predators such as spiders don’t have any issues squeezing through the tight spice. However, even a small mouse will not crawl through a 0.11-inch opening.
3. To seek out a safe space to lay eggs in
Tight spaces are ideal locations to lay eggs. Cockroaches rarely lay eggs in wide-open areas as these are exposed to predators. They prefer to lay eggs in small openings underneath furniture, wall cracks, and other areas that are very difficult to reach to other species.
Cockroaches can squeeze through very tight spaces. They do this by flattening their bodies. Making it through small spaces is not an exception as roaches move together, one at a time, through the same small opening.
Roaches might prefer these very tight spaces as a means to enter homes, as the only method of reaching a certain area with food or moisture, or when seeking out an ideal location to lay eggs in. Roaches routinely escape through tight spaces when they face a threat such as mice or pesticides.