Cockroach vs Water Bug: 5 Key Differences Explained

Written by AZ Animals Staff
Published: August 11, 2021
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Both cockroaches and water bugs are extremely common pests in the United States. They infest the same areas in the home, too, such as the basement, bathroom, kitchen, or laundry room. And have you ever heard of any cockroach being referred to as a water bug? If you think that implies a water bug is a type of cockroach, you’d be right. The term “water bug” is broad and can apply to several different insects that live in freshwater or on the water’s surface. The amphibious cockroach is just one of 1500 species of water bugs, whereas cockroaches are land-dwelling.

While dealing with them as pests, it is useful to tell the difference between the two to better handle them. Even without an infestation, it is helpful so you can be prepared if you ever encounter them. We’ll go over all their differences below!

Comparing Cockroach vs Water Bug

CockroachWater Bug
Size.075-3 inches long2-4 inches long
ColorRed, brown, tan, blackBrown, tan, grey (Oriental is darker)
BodyFlat, oval body, no wings, long antennae, spine-covered legs, downward-facing headFlat, oval body, wings, short antennae, piercing mouth, pointed beak, clawed front feet
HabitatWarm, dark indoorsMoist, dark freshwater ponds, lakes; near lights
TaxonomyOrder Blattodea, different families, genera, and speciesBlatta orientalis or true waterbug (true bug order Hemiptera, infraorder Nepomorpha)
Group behaviorGroupSolitary except during the mating season
DietScavengerPredatory,  scavenger (algae, garbage)
TerminologyLand-dwelling cockroachAquatic, Oriental cockroach

5 Key Differences Between Cockroach and Water Bug

Cockroach vs Water Bug: Size

A waterbug always dominates a cockroach in size, measuring anywhere from 1 to 3.25 inches longer than any cockroach. Even if you don’t see them side-by-side, you can still have a good idea of which is which.

Cockroach vs Water Bug: Body

When discussing physical features, it’s important to keep in mind that we are simply distinguishing the Oriental cockroach, also called a water bug or black beetle, from land-dwelling cockroaches. The American, Smokybrown, German and Oriental cockroaches are all called “water bugs,” but the only aquatic species is the Oriental. Cockroaches all have flat, oval bodies with antennae. The land-dwelling roaches have long antennae, spine-covered legs that look hairy, downward-facing heads, and no wings. Water bugs, or Oriental cockroaches, have short antennae, wings, clawed front feet, a pointed, short beak, and piercing mouth.

Cockroach vs Water Bug: Habitat

The land-dwelling cockroach is adaptable, although it prefers warm, dark enclosed spaces, and will move indoors to escape the cold of winter. The water bug, on the other hand, prefers moist and dark areas near freshwater ponds and lakes. It is also seen flying near lights during mating season. Not only does a cockroach not have any wings, although some species can glide, it also shies away from any light. This is why cockroaches run away when you turn the light on in a previously dark room.

Cockroach vs Water Bug: Group Behavior

Cockroaches enjoy being surrounded by each other as often as possible. Water bugs are fairly solitary except for mating season. So if you encounter either one, a little more peeping around will tell you its group behavior and indicate which one it likely is.

Cockroach vs Water Bug: Diet

Both of these roaches can be scavengers. The difference is the predominant diet. Cockroaches are scavengers and will feed on food, garbage, and rotting things. Water bugs are predatory and will hunt smaller creatures, but they’ll also feed on algae and garbage whenever possible.

Next up: Caribou vs Elk: 8 Main Differences Explained

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About the Author

AZ Animals is a growing team of animals experts, researchers, farmers, conservationists, writers, editors, and -- of course -- pet owners who have come together to help you better understand the animal kingdom and how we interact.

FAQs (Frequently Asked Questions) 

What is the difference between a Water Bug vs Cockroach?

A water bug is an Oriental cockroach that lives near water, whereas a cockroach lives on land. While any roach can be commonly called a water bug, the only aquatic roach is the Oriental cockroach.

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