What Is The Difference Between a Water Bug and a Cockroach?

Last Updated on December 6, 2021 by Kimberly Crawford

Cockroaches are pesky and we do not want them around the house because they contaminate food, carry unknown bacteria that could cause disease, and are just distracting to see. But sometimes, what you see in a room might not be a cockroach but some uncanny lookalike like the water bug. 

In this post, we narrow down the similarities and differences between water bugs and cockroaches.

Although confused with one another, they have different identifiers. But both need to be addressed when you suspect infestation in your home. So, without further ado, read on.

Related: Cockroach Infestation- Signs, Health Impact, Treatment, and More…

the differences between water bug vs cockroach

What is a water bug?

As the name implies, water bugs live or thrive in water, and they belong to the order Hemiptera. There are hundreds of water bug species but the most popular would be water spiders and the water scorpions.

Water bugs are also known as alligator ticks in the south. This insect resembles American and oriental cockroaches the most. 

Like cockroaches, water bugs can bite and may leave painful bites when disturbed. Because they do not discriminate when it comes to their aquatic niche, they can bring in bacteria in the home and contaminate food items as well as the water we drink. 

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Where do water bugs live?

As we have already mentioned, water bugs live in water or near water features as well as moist and damp areas in the home. As such, they thrive in gardens, ponds, fountains, pools, as well as under the sink, bathrooms, and basements.

They also live in below ground level fixtures such as in sewers, pipes, and more. During winter and fall, they find ways to migrate indoors because they die at low temperatures. 

Water bug facts

giant water bug

Before we go into the essentials of differentiating water bugs from cockroaches, let us first get to know water bugs more through these facts about this roach look-alike. 

  • The giant water bug is considered as the largest true bug in the world at 5-inches in length. It is found in South America. 
  • Giant water bugs are more dangerous compared to other species because they tend to be cannibalistic. 
  • At least one variety of water bugs are afraid of flood and flood water. 
  • Some species of water bugs are also found on sea sides. 
  • The average litter size of water bugs contains 100-150 of these insects. 
  • The most popular species of water bugs would be the giant water bug, water boatman, water strider, water scorpion, and backswimmer.  
  • Water bugs can live for four straight weeks without food and two weeks without water. 
  • Water bugs are drawn to artificial light but would die under long exposure to natural light. 

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What causes water bugs in your house?

types of giant water bugs

The reasons why water bugs are in your home are the same as why roaches love to niche in your space. The following are the most common causes as to why water bugs are in your house. 

  • Moisture: Well, we have already said that water bugs are aquatic insects so if you have damp and moist areas such as an unfinished basement, under the sink, crevices or with standing water, you are giving them a niche to thrive on. 
  • Insect infestation: Unlike cockroaches, true water bugs feed on small insects through their biting mouthpiece. If your home harbors ants, mosquitoes, and other prey, they can be attracted to your home. 
  • Dark areas: Aside from the dampness of dark areas, water bugs also love the consistent humidity level of dark rooms. Specifically, they would thrive in between 70-85F but at a temperature of 15 degrees below, they would die. 
  • Decaying organic matter: You would also usually find them around trash bins, compost, and even in mulches in your yard. They scavenge like cockroaches, and this is yet another reason why water bugs are often confused with roaches. 

Similarities between water bug and cockroach

There are subtle similarities between cockroaches and water bugs making it hard to tell which one is which when they both run fast at night. In terms of appearance, they share the same shiny, brown color, oval shaped bodies, and a generally flat appearance. In terms of behavior, water bugs and roaches are both nocturnal. 

You would be surprised to know that this is where all the similarities end for cockroaches and water bugs. It is more interesting to take note of their differences if you want to be better in extinguishing both insects from your home. 

Related: 12 Bugs That Look Like Cockroaches (But Aren’t)

Differences between Water bug vs cockroach

water bug vs cockroach

It is astonishing to know that there is a wide range of differences when it comes to water bugs and cockroaches even if they are confused with each other most of the time. Here are some of the most notable differences between these two insects. 

1. Size

Water bugs tend to grow bigger than roaches. Water bugs can have a size of 2-4-inches while roaches stop at 1.5-inches. 

2. Appearance

In terms of color, water bugs stick to gray or dark brown while roaches range from red or brown. If you find a prominent reddish tint in the body, that would most likely be a cockroach. As for the antennae, both sport a pair but water bug antennae are shorter. 

For the wings, some roaches have wings while others do not. In contrast, water bugs have an X-shaped pair of wings. Furthermore, roaches do not have clawed legs compared to water bugs. The latter also have sharper proboscis, made for liquefying their prey and roaches do not have one. 

3. Life cycle

In terms of phases, roaches and water bugs are similar but as for longevity, roaches, depending on type can live from 110-700 days while water bugs live for 365 days at maximum. 

4. Habitat

Roaches and water bugs could thrive in damp, dark, and moist areas like basements, under the sink, bathrooms, pipes, and sewers. But to add to these, the natural habitat of water bugs would be ponds, marshes, and pools. 

5. Swimming

Roaches cannot survive underwater and their manner of threading through water would be more of floating than swimming. On the other hand, water bugs could swim like maggots. This is understandable since they are aquatic insects. 

6. Eating habits

Roaches eat by scavenging while water bugs eat by preying on smaller insects. They claw their feet on their prey, and then inject their proboscis on the softer parts of these insects’ bodies until they are liquefied enough to be eaten. 

7. Diet

As scavengers, roaches thrive on decaying organic matter, starchy food items and materials like cardboard or paper. In contrast, water bugs feed on small fishes, bugs, crustaceans, snails, and tadpoles. 

8. Temperament

Roaches are shy. They are most likely to run away fast in the presence of humans. They are also mostly found in more limited routes. On the other hand, water bugs are more visible and as such, can infest more areas at a time compared to roaches.

They are both biters when disturbed but water bugs are more aggressive than cockroaches and are also known to have more painful bites than roaches. 

9. Droppings

Both shed molts and casings but water bug casings are easier to find than roaches. In terms of color, water bug droppings are larger, more cylindrical in shape and are often brown in color compared to the smaller, black colored and flatter droppings of cockroaches. 

10. Most active

Both are active at night, but roaches are specifically active year-round and at 70F at least. On the other hand, water bugs are most active at night during summer and fall. 

11. Pest determination

Without a doubt, cockroaches are considered as pests, specifically high hazard pests. In comparison, water bugs are not tagged as pests but as predators since they prey on pests and other smaller insects. 

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Other than these similarities and differences, there is also other information that you should know about water bugs.

These could help you in mitigating water bug infestation in your home or to prevent one from ever happening in your space. As such, here are some FAQs about water bugs that you should be aware of. 

Do water bugs crawl on beds?

They are very rarely indoors so it would also be rare to find water bugs in bed. But in some rare circumstances where they are found in beds, it is said that they are most likely to bite because they get attracted to human sweat and skin cells. Even then, this would not cause them to bite the sleeping person. 

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Are water bugs bad?

Yes. Aside from the bacteria they can potentially carry, having them around would mean that there is another insect infestation happening around and you do not even know it.

Note that they prey on smaller pests and insects, which in themselves are also infesting your home. So, you can say that it is more of a food chain process happening in your home if you want to downplay the word infestation. 

What do water bugs do?

giant water bug on home

When it comes to water bug behavior and their effects, these insects are not different from roaches. Water bugs are hard to kill, and they are prolific breeders. Their molts for one, can cause allergic reactions to humans and may induce asthma attacks.

Apart from these, they can also bring in bacteria and spread them around the home. As such, food can be contaminated, causing stomach aches and other diseases. 

With these, it is recommended that a homeowner do something to address the problem. Starting with consulting a professional pest control company would help. 

Related: I Saw One Cockroach. Should I Be Worried?

Can water bugs come up through toilets?

Fortunately, no, even if they have water on them. But other drains are not invulnerable to water bugs so you should know that they can come up in other bathroom fixtures such as sink, shower drains, and even bathtubs. This is something that they share with roaches too. 

Do water bugs play dead?

Fun fact, water bugs are crafty and yes, they tend to play dead whenever a larger predator is around, humans included. They do this survival method of theirs by excreting a fluid through their anus.

This makes them freeze on the spot. After the threat is gone, they come alive and become aggressive. This special venom of theirs is also the reason why they have more painful bites compared to roaches. 

Do water bugs get attracted to light?

Yes, especially during mating season.

While there is no definite explanation to this, water bugs are mostly seen during summer or the mating season, in clusters, flying around porch lights, under streetlights in parks, and even trailing along car lights.

This is the reason why they are also sometimes called the electric light bug. 

Where are water bugs during the day? 

Like termites, water bugs travel within walls, chewing the foundation one at a time for them to build nests. Because they have this travelling ability, they are more likely to build nests in different locations at once.

Like other insects, they stay in these nests during the day and leave them at night to catch prey. 

Do water bugs bite?

giant water bug lethocerus deyrollei

Yes, but rarely among humans. If you ever find yourself bitten by one, it means that you have disturbed their habitat, or they were threatened by your presence.

Although water bug biting seldom happens, you should know that their bites are painful and can trigger an allergic reaction. Some symptoms of water bug bites would be the following: 

  • Pulsating pain
  • Itching and red bumps
  • Burning sensation (mild)

Related: Cockroach Bites: Signs, Dangers, Prevention, and Treatment (With Pictures)

How to treat water bug bites

If for some rare chances you have been bitten by a water bug, here are some first aid tips that you should employ if you ever get bitten by one. 

  • Wash the bitten area with soap and warm water. 
  • Prepare a homemade paste composed of one part baking soda and one part water. Apply the paste to the bitten area and leave it to dry for an hour. 
  • Rinse the paste with cold water. 
  • Itchiness and inflammation can still ensue and for this, you can use some old-fashioned lemon juice or just buy a hydrocortisone cream from the pharmacy. 
  • To reduce swelling and redness, also apply aloe vera cream to the bitten area. An ice pack would also do the trick. 

How do I get rid of water bug infestation?

The steps in getting rid of a water bug infestation in the home are almost the same steps that you would have to do in getting rid of roaches. Here are some of the most common methods in getting rid of water bugs in the home. 

  • Boric acid: Regularly sprinkling borax under the sink, in the basement, or around moist and damp areas where water bugs niche is an effective way to get rid of water bugs and roaches alike. The chemicals in the borax destroy their digestive system when they ingest the dust. 
  • Food grade diatomaceous earth: You can use this product around the garden or in the home. The chemical substances in it crack the shell of water bugs. Without their protective covering, they would die. 
  • Algaecide: Being the aquatic insects that they are, the pool can offer a good niche. You can use pool cleaners and algaecides to eliminate all their food sources in the water. 
  • Vinegar/alcohol spray: This old-fashioned solution is effective in getting rid of waterbugs. Just mix one-part white vinegar and one part water and spray the solution in the common areas where they are usually found. Diluting alcohol in one part water can also be used as a substitute for vinegar. 
  • Essential oils: Like most pesky insects, water bugs also hate strong, aromatic smells. Diffusing essential oils around the home, especially in the basement, study areas, and other spaces where they can thrive, is effective in hampering water bug infestation. 
  • Professional help: If you have done everything that we have listed here and still water bugs are seen roaming around, maybe it is time to call in professional help to exterminate these pesky insects. 

Related: How to Get Rid of Cockroaches and Keep Them Away

How do I prevent future water bug infestation?

Once you have extinguished the water bugs in your home, it is essential to take precautionary steps to inhibit them from finding their way indoors yet again. Here are some tips to take in making sure that future water bug infestation is prevented. 

  • Deep cleaning: Give your home a round of thorough cleaning. Remove all standing water, clean the pool regularly, make sure that everything is neatly tucked, and all spaces are tidy. Also, disinfect damp and moist spaces regularly. 
  • Food items: Make sure that the pantry is sealed tightly. Also ensure that all containers are airtight so that the water bugs would not find themselves catching small insects smuggling food from the pantry. Algae and maggots around the pool and standing water should also be addressed. 
  • Seal cracks: Even if it is not yet the regular spring cleaning, you must seal all crevices, leaky faucets, and pipes. Doing this would eliminate entry points for them to come into your home. 

What are the best essential oils to kill water bugs?

If you are more into natural remedies in killing off water bugs and find the use of essential oils as the best method for you, here are the best rated essential oils to kill water bugs. 

  • Oregano oil
  • Rosemary oil
  • Catnip oil
  • Cedar oil
  • Peppermint oil
  • Cypress oil
  • Citronella oil
  • Tea tree oil
  • Eucalyptus oil
  • Lavender oil
  • Mint oil

How do you kill water bugs in swimming pools?

If you think algaecides and pool cleaners take a lot of time in killing water bugs in pools, you should try pouring 3-5 teaspoons of liquid dish soap in the area where the pool light is brightest.

Because they are naturally drawn to light, they would naturally swarm in that area. With the thick mantle of liquid dish soap there, they cannot swim through and would eventually drown. All that is left is to scoop them out after. 

What smell do water bugs hate? 

All strong, overwhelming smells are pungent for water bugs. But of all these imposing odors, it is said that water bugs particularly avoid the scent of peppermint. This is the reason why it should be the priority essential oil to purchase for naturally repelling water bugs away from the home. 

What time of the year do water bugs come out?

As has been mentioned here, water bugs love summer. They love moist and high humidity. As a matter of fact, they thrive and become very prolific breeders at 70-85F.

During fall and winter, rates of home infestation become high. The reason for this is that the damp, moist spaces in your home have their humidity range. On the field, they die off at 15F and below. 

Are water bugs all cannibals?

Fortunately, no. Only the giant water bugs are known to show cannibalistic tendencies at maturity.

The good thing is that this species of water bugs would never enter your home, ever. So, its most common prey would be other types of water bugs but reports also say that they can swarm around larger animals like snakes, ducks, and bigger wild birds. 

Are water bugs considered beneficial?

Interestingly, among landscapers, water bugs are considered beneficial because they are the main predator of pests and insects that chew on plants and vegetables. But once they find the comfort of your home, they could be pesky and hard to kill.

As such, best manage their litter while their numbers are still manageable. 


Differentiating water bugs from roaches or from any other insect look alike for that matter, comes in handy because it would give you a vantage point on how to treat and extinguish them from your home.

They might look similar in size, color, and general appearance, but their behavior and other characteristics could help you in identifying which is which. 

With all that we have covered here, it would be easier for you now to delineate a water bug from a cockroach, specifically American and oriental roaches from water bugs. With these new found information, terminating them due to a suspected infestation should be easier now too.