A typical US household is more likely to be infested with a cockroach than a water bug. Although they may look similar, differentiating them is pretty easy because of many differences.
Interestingly, both are part of Insecta but are grouped differently (Cockroaches under order Blattodea whereas water bug Hemiptera).
Water bugs are outdoor species with more significant and flatter bodies than cockroaches; they have two legs and much shorter antennas sitting under the eyes.
Unlike dark brown roaches, they have a greyish color and yellow stripes behind the head. Water bugs love to live near water bodies and prey on other aquatic animals.
Water bug is also known as Giant Water Bug, Electric Light Bug, and Giant Fish-killer.
I have elaborated 15 differences between roach and waterbug with pictures, including their origin, size & color, habitat, feeding habits, and ways of reproduction.
Moreover, cockroaches can differ from water bugs in their lifespan, flying capabilities, infestation, and spreading diseases.
Although cockroaches rarely bite whereas water bugs, if disturbed, can sometimes bite in self-defense.
The bite can be painful but is devoid of any severe consequences. After going through the blog below, I am convinced you will quickly differentiate between water bugs and cockroaches.
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1. Origin of Water Bug vs. Roach
Although the origin of American cockroaches can be traced back to tropical climates of Africa.
On the other hand, water bugs are thought to be originated from the black and Caspian seas (some biologists associate them with Russia and Africa).
2. Size and Color of Water Bug vs. Cockroach
There is a marked variation in size and color among different cockroaches. Adult roaches can range from 10mm up to 53mm. The color also varies from light to smokey and dark brown.
In contrast, water bugs are flatter, with large sizes ranging from 50mm to 100mm. The color of the water bug is more tilted towards a greyish hue. Moreover, a strip of yellow markings usually covers the area behind the head.
Water bugs have antennas smaller than their heads than roaches, which is a prominent differentiating feature.
4. Habitat of Water Bug vs. Roach
All cockroaches have an origin in the outdoors. American roaches and water bugs both love to live outdoors. Whereas both can infest homes, water bugs will very rarely do so. Cockroaches love warm and humid environments and are usually located inside bathrooms, garbage, basements, and food storage cabinets.
However, german roaches can severely infest homes as they love living indoors.
On the other hand, as the name suggests, water bugs are located near water bodies like lakes, ponds, and streams. Thanks to their air storage capabilities. Water bugs can survive under the water for many hours.
5. What does Water Bug Eat?
Cockroaches are omnivorous and feed on leaves outdoors. Inside the home, they live on leftovers, including garbage, fruits, and pieces of bread. Besides these, roaches love to eat starchy foods, mainly bakery items.
On the other hand, water bugs are picky and usually prey on fishes, amphibians, and aquatic insects. They release a powerful enzyme that can paralyze the prey.
6. Reproduction Cycle of Water Bug vs. Cockroaches
Reproduction is the cornerstone for the survival of species. Cockroaches prefer to reproduce in the late humid summer season. An adult female American cockroach lays eggs 55 days after mating. The baby cockroaches undergo molting to transform into eggs.
It is pretty interesting to know that male and female water bugs actively participate in reproduction. Once the female bug finds an appropriate male partner, she mates and lays eggs on the wing of the male bug after 55 days. The male then takes care of the eggs and periodically visits water to prevent the eggs from drying out.
The eggs hatch after 45 days, and the larva is born. The larva undergoes five staged metamorphoses before transforming into an adult water bug.
7. Life Span of a Water Bug vs. roaches
Interestingly, male American cockroaches have a shorter life span than female bugs by up to 3 months.
The life cycle of cockroaches is, on average, two years. This can vary between different environments and places. A cockroach’s life span also depends on the availability of food and water. You can read more on how long a cockroach lives here.
Although adult water bug has a similar life span to cockroach, the life span from eggs to death is shorter by up to 6 months.
This is because the nymphal stage in water bugs is shorter, with only 4 to 5 molts taking almost 2 to 3 months to transform into adult bugs.
8. How do water bugs Communicate?
Regarding communication, cockroaches have a complex organized method of communicating with each other.
This is achieved through a variety of chemical odors called pheromones. The composition of these pheromones changes according to the message. They can pass information about food, danger, and mating.
The water bugs communicate with their colony through water ripples, known as ripple communication. The verticle oscillation of the legs creates a cascade of waves that another member picks up. The water bug can transmit messages, including food, mating danger, and territorial guarding (Source).
9. Roach vs. water bug flight
Cockroaches don’t fly regularly; when they do, they mostly glide for a short distance. Some cockroaches are heavy enough that they are intrinsically designed to crawl.
Cockroaches fly in case of imminent threat and only when the conditions are ideal. Likewise, not all roaches fly; only adult Smokybrown and American cockroaches can fly.
Water bugs, on the other hand, are good flyers. They have two sets of wings, one larger and darker than the other. They usually fly during the late humid summer months, when it’s ideal for mating. The water bug flies from one water body to another.
They can fly 30 to 50 meters in one go. Like other insects, water bugs are attracted to bright lights, and you can occasionally see them flying toward the light sources.
10. Defense mechanism of water bug vs. Cockroach
When it comes to defense mechanisms, cockroaches have a very unique and sophisticated system. The defense mechanism is adopted to serve two functions
1. To act as an emergency escape system from a threat, and
2. To serve as a signaling mechanism, informing the colony about an imminent threat.
Florida cockroaches spray a foul-smelling liquid on the prey, which acts as an irritant and a signal. It is essential to know that these roaches have a limited juice supply; it takes three months to refill.
On the other hand, when they feel threatened, water bugs can play dead or even bite. The bite is a powerful defense mechanism that paralyzes the prey or elicits a painful response from predators, including humans. They can also emit unpleasant odors from their anus, which wards off predators.
11. Image of Water Bug Eggs vs. Roach Eggs
American cockroaches produce eggs 55 days after mating and hatches after 45 days.The eggs are encased in a light brown sac called ootheca.
Interestingly, ootheca is visible to the naked human eye and measures a few millimeters. Each egg sac contains between 13 to 15 individual eggs. Learn more about roach eggs here.
Female Water bug lays eggs in batches of 100 plus eggs. The eggs are creamy colored and resemble the seeds of the sunflower.
Some water bugs lay on the green vegetation while others on the back of the male partner. The selection of place depends on the species of water bugs. It just takes two weeks for the eggs to hatch.
12. Water Bug Babies vs. Roach Babies
Cockroaches can multiply quickly. An adult female American roach keeps producing an ootheca (Containing approximately 15 individual eggs) every month for the rest of their life.
At the end of her life, she will have given rise to approximately 120 to 180 offspring. Since cockroaches live in hiding, their survival rate is high.
Conversely, an adult female water bug will produce between 150 to 400 eggs in her lifetime. The number of eggs produced depends upon the optimal conditions and environmental temperatures. An adult female water bug can give rise to between 100 to 300 offspring in her life.
One study produced the highest number of eggs (420) at 24 degrees Celcius (Source). The eggs on the back of the male partner are most likely to hatch with a 97% probability.
The survival rate of water bug babies is low due to their diet or being prayed by other animals.
13. Water bug Bite vs. roach bite
Cockroaches, like other roaches, scavenge on rotting food and leaves. They are almost innocent when it comes to biting humans. This does not mean that they are not able to bite.
They can and do bite sometimes when disturbed. The bite is trivial, primarily with very few cases of severe pain. You can read more on Do Cockroaches Bite? Here.
Likewise, Water bugs are scavengers and are known to bite. They also can bite humans, but only when they feel threatened.
They bite with the help of proboscis and mouthpiece, injecting a powerful enzyme that can liquefy host tissue and paralyzes their prey. Their bite is mostly not dangerous to humans but can sometimes cause pain and severe allergic reaction, requiring medical consultation.
14. Health Risk
Cockroaches are known to transmit diseases. An infested cockroach can transfer enteric fever (Salmonella Typhi and Para Typhyi) from feces to food or kitchen surface.
They are also known to elicit allergic asthmatic attacks in atopic people. The cause for allergic reaction is mainly the pieces of exoskeleton molt. Learn more about: Are Cockroaches Dangerous?
Water bugs are known as toe biters. Their saliva is usually non-toxic to humans, but their bite can cause immense pain or sometimes even cause a complete or partial loss of sensation in the bitten area (hypoesthesia).
Although it is usually thought that water bugs do not transmit any disease, a recent study in West Africa Concluded that they might cause Buruli Ulcer (Caused by Mycobacterium Ulcerans, whose incidence is increasing steadily) (Source).
15. How to get rid of water bugs?
Although recent advances in chemical pesticides have proven disastrous for roaches, eliminating roaches can pose some serious challenges. Boric acid, chemical sprays, and bait traps are proven to be lethal to cockroaches. You can also use natural cockroach repellents if you want to ward them off without squashing them to death.
Likewise, chemical pesticides, boric acid, and detergents can be used to kill water bugs effectively. I prefer using boric acid to kill water bugs because it not only kills water bugs but also stays on the surface for a long.