Essential Facts About Water Beetles: A Quick Guide

folder_openColeoptera, Insecta
comment12 Comments

Water beetles are fascinating creatures that can be commonly found in various aquatic environments. These insects play a vital role in maintaining the health of freshwater ecosystems, as they are both predators and herbivores. To help you better understand these aquatic insects, let’s dive into some interesting facts about water beetles.

You might be surprised to know that there are different types of water beetles. Some notable examples include the giant water scavenger beetle, which is the largest aquatic-dwelling beetle in the United States, and the predacious diving beetles that make up about half of all water beetle species. These beetles can be found in diverse habitats, such as in dense vegetation, standing water, and slow-moving rivers and streams.

One of the unique features of water beetles is their ability to breathe underwater. For instance, the silver-beetle can break through the surface film of water using its “un-wet-able” antennae, which form a funnel for transporting air. This is just one of the many captivating aspects that make water beetles an essential part of aquatic ecosystems.

Overview of Water Beetles

Water beetles are fascinating aquatic insects that can be found in various aquatic environments. These insects play an important role in the ecosystem, as they help break down dead materials and serve as a food source for other animals.

One well-known water beetle is the giant water scavenger beetle, which can grow up to 40 mm in length. They have the ability to exchange air in their breathing bubble by rising to the surface and making contact with the air using their long maxillary palps.

As you explore the world of water beetles, you’ll discover that they vary in size and features. Some common characteristics include:

  • Aquatic adaptations such as specialized legs for swimming
  • Ability to breathe underwater using air bubbles
  • Unique feeding habits and preferences

Comparing water beetles to other aquatic insects, you’ll find they have some similarities, such as their aquatic adaptations. However, they also have unique features that set them apart from other insect groups. For example, water beetles have thicker, more robust bodies, which help them withstand the pressures of living in water.

In summary, water beetles are fascinating creatures that play an essential role in aquatic ecosystems. Whether you’re an insect enthusiast or just curious about these aquatic critters, learning more about them can reveal a captivating world just beneath the water’s surface.

Physical Characteristics

Color: Black, Brown and Yellow

Water beetles come in a variety of colors, including black, brown, and yellow. Their coloration helps them blend into their aquatic environments. For example, the giant water scavenger beetle is known for its black color.

Water Beetle Exoskeleton: Elytra and Hair

A water beetle’s exoskeleton is one of its most critical features, providing protection and support. The hardened forewings, or elytra, cover and shield the delicate hind wings and abdomen. In addition, some water beetles, like the crawling water beetle, have hairs on their exoskeleton that help trap air bubbles for underwater respiration.

Adaptations: Physical Gill and Spiracles

Water beetles have unique adaptations to thrive in aquatic environments. Using a physical gill, they can extract oxygen from the water they inhabit. Spiracles, small openings near their abdomen, serve as breathing tubes when beetles surface for air.

Fur on Water Beetles

Some water beetles, such as the crawling water beetle, possess fur-like hairs on their bodies. This fur helps trap air bubbles, allowing the beetle to stay submerged for extended periods of time.

Water Beetle Size

Water beetles can greatly vary in size, ranging from just a few millimeters to over 3 inches in length. The giant water scavenger beetle is an example of a larger beetle, measuring up to 1.57 inches in length.

In conclusion, water beetles display fascinating physical characteristics that enable them to thrive in aqueous habitats. Their diverse range of colors, hard exoskeletons with elytra and hairs, unique breathing adaptations, and varying sizes make them interesting creatures to study and admire in the world of insects.

Water Beetle Habitats

Water Beetles in the United States

In the United States, water beetles can be found in various habitats such as ponds, lakes, and slow-moving streams. These habitats provide ample vegetation for water beetles to feed on and thrive in. The giant water scavenger beetle, for example, is the largest aquatic-dwelling beetle in the US and can be found across the continental states.

Water Beetles in Japan

In Japan, water beetles make their homes in diverse aquatic environments like rice paddies, shallow ponds, and marshes. The humid climate and abundant plants in Japan create ideal conditions for these beetles to inhabit and reproduce.

Littoral Zone: Home to Water Beetles

The littoral zone, which is the area near the shoreline of a body of water, is a prime habitat for many species of water beetles. This zone is rich in plants and provides food, shelter, and breeding grounds for these insects. Some common features of this habitat include:

  • Shallow water
  • High vegetation density
  • Dynamic conditions due to tides or water level fluctuations

Intertidal Zone: Habitat for Marine Species

The intertidal zone is another important habitat for marine water beetles. It is the area between the high and low tide marks on a shoreline. This constantly changing environment offers a variety of suitable microhabitats for different species of water beetles. Key characteristics of this zone include:

  • High humidity levels
  • Fluctuating water conditions
  • Terrestrial and marine vegetation

Water Beetle Habitats: Pools and Fresh Water

Small pools of fresh water, such as ponds and puddles, serve as habitats for water beetles. These small bodies of water provide vegetation and the right temperature for beetles to survive and search for food. The presence of other animals, such as fish and amphibians, also create a balanced ecosystem where water beetles can thrive.

In conclusion, water beetle habitats are diverse and plentiful across various geographical regions. These insects are adaptive to a range of environments, making them successful occupants of aquatic ecosystems around the world.

Water Beetle Life Cycle

Eggs and Hatching Process

Water beetles begin their life cycle as eggs. Female beetles lay their eggs in or near water, usually on submerged plants or rocks. The eggs usually hatch within 7 to 10 days, depending on the species and environmental conditions. You might observe clusters of small, round eggs underwater during the warmer months.

Larvae of Water Beetles

Once the eggs hatch, the larvae emerge. Water beetle larvae are different from the adult beetles you’d typically see, as they are usually much more elongated and have longer legs. They are well adapted for life underwater:

  • Active predators
  • Can swim quickly
  • Have strong jaws for catching prey

The larval stage may last several weeks or up to a year, depending on the species and environmental factors such as temperature and food availability.

Pupating Stage

After the larvae have fully grown, they undergo pupation. This is the transformation stage where the larva turns into an adult beetle. The larvae usually leave the water or settle into a safe area to pupate. During this stage:

  • The larva forms a protective case called a pupal cell
  • Inside the pupal cell, the larva undergoes metamorphosis
  • This process takes anywhere from a few days to several weeks

Adult Water Beetles

Once metamorphosis is complete, an adult water beetle emerges from the pupal cell. Adult beetles are equipped with features for living in an aquatic environment:

  • Short, clubbed antennae
  • Aquatic adaptations for respiration
  • Swimming abilities

Adult male and female beetles participate in mating, and the female will lay eggs to start a new generation. The adult life stage can also range from weeks to a year, depending on the species, environmental factors, and predation risks. Throughout their life cycle, water beetles face various challenges and play important roles in their ecosystems, from being predators to serving as food for other animals.

Food and Predators of Water Beetles

Diet: From Dead Insects to Small Fish

Water beetles have varied diets, depending on the species. Some primarily consume dead insects and other organic matter, providing a valuable clean-up service within their aquatic habitat. On the other hand, certain species, like the predaceous diving beetles, hunt live prey, including small fish.

As a water beetle owner, you can provide a mix of live and dead insects for your pet’s diet. Examples of suitable food include:

  • Bloodworms
  • Daphnia
  • Brine shrimp

Predators: From Birds to Lizards

Water beetles face various predators in the wild. Birds, such as herons and kingfishers, frequently catch and eat these aquatic insects. Other animals, like frogs and lizards, may also prey on water beetles, while small fish and other insects may eat their larvae.

When keeping a water beetle as a pet, it is essential to provide a secure and spacious habitat, ensuring its protection from potential threats. A well-maintained tank with appropriate hiding spots and optimal water quality will help your pet thrive.

Although water beetles are fascinating creatures, it’s important to remember their place in the ecosystem and the threats they may face. By understanding their diets and the predators they encounter, you can better appreciate these intriguing insects and provide suitable care for a pet water beetle.

Different Types of Water Beetles

Dytiscidae: Diving Beetles

Dytiscidae, also known as diving beetles, are a diverse group of insects. These beetles have large, flat bodies and hind legs designed for swimming. Some examples include:

  • Dytiscus marginalis – Great Diving Beetle
  • Hyphydrus ovatus – Striped Diving Beetle

Haliplidae, Noteridae, and Amphizoidae: Unique Species of Beetles

These families have unique adaptations for living in water:

  • Haliplidae: Also known as crawling water beetles, they have flattened hind legs for swimming.
  • Noteridae: Burrowing water beetles, they use hair-like structures for air retention.
  • Amphizoidae: Troutstream beetles, their elongated body helps them cling to rocks in streams.

Gyrinidae: Whirligig Beetles

Whirligig beetles belong to the Gyrinidae family. They’re known for their erratic swimming on the surface of the water. Unique features:

  • Eyes divided into two parts, for seeing above and below water.
  • Legs modified for rowing.
  • Whirling motion for escaping predators.

Hydroscaphidae: Skiff Beetles

Skiff beetles, from the Hydroscaphidae family, possess characteristic features:

  • Small size, around 1.5 mm in length.
  • Lateral extensions on their abdomen.
  • Live in fast-flowing streams under stones.

Hydrophilidae: Adult and Larva

The Hydrophilidae family includes water scavenger beetles. Adults can filter-feed on organic matter while larvae are predators.

  • Hydrophilus triangularis is an example of a giant water scavenger beetle.
  • Their larvae have sickle-shaped mandibles for catching prey.

Travertine Beetles: A Rare Species

Travertine beetles are found in mineral-rich springs and lakes. Their unique features:

  • Dwelling among calcite formations.
  • Adapted to living in extreme conditions with high mineral content.

Lutrochidae, Heteroceridae, Sphaeriusidae: Other Types of Water Beetles

These families also contribute to the diversity of water beetles:

  • Lutrochidae: Lutrochus beetles have compressed bodies, swim under rocks in shallow waters.
  • Heteroceridae: Variegated mud-loving beetles, found in muddy habitats near water sources.
  • Sphaeriusidae: Minute bog beetles, inhabit wetlands and are known for their minute size (0.5-1 mm).

By learning about these diverse types of water beetles, you can better appreciate the fascinating world of aquatic insects.

Water Beetles as Pets

Water beetles can be interesting pets, especially for those with a deep fascination for insects. If you’ve been considering the world of pet beetles, you’ll find that these aquatic creatures offer unique and engaging opportunities.

When looking to keep water beetles, be prepared to invest in a proper setup, since their environment plays a key role in their health. Some essentials include:

  • A suitable tank, preferably at least 5 gallons in size
  • Water that is clean and dechlorinated
  • A secure lid to help maintain proper humidity and prevent escapes
  • Hiding spots like submerged plants or pieces of driftwood
  • A heater and a filtration system for optimal water conditions

Water beetles are generally low-maintenance. Feeding can be done every couple of days, as they typically consume a variety of decaying organic matter found in their environment. This might include various insects, fish, or plant material.

One of the fascinating aspects of water beetles as pets is their ability to store an air bubble to breathe underwater. You may observe your water beetles rising to the surface to replenish their air supply, which is an intriguing sight to behold.

It’s essential to keep your water beetle tank clean, as stagnant water can lead to harmful bacteria growth. Regular water changes and filter maintenance will help ensure the health and happiness of your little aquatic friends.

In summary, if you’re up for a unique pet experience and have a keen interest in the insect world, water beetles may be the right choice for you. With their unusual habitats and behaviors, they can provide endless fascination and enjoyment. Just make sure to invest in the proper care and maintenance to keep your new pets happy and healthy.

Water Beetles and Human Interaction

Biting: A Defense Mechanism?

Although not all water beetles bite, some species can bite when they feel threatened. These bites are rarely severe, but might be painful for a short period of time. Remember, the beetles are not aggressive by nature; they simply use biting as a defense mechanism.

For example, giant water scavenger beetles (Hydrophilus triangularis) are known to bite but only if they feel threatened 1. If you encounter a water beetle, it’s best to avoid handling it to prevent potential bites.

Insecticides: Their Role in Control of Water Beetles

In some cases, controlling water beetle populations might be necessary, especially when an infestation occurs. Insecticides play a significant role in controlling these pests. Some common insecticides used for managing water beetles include:

  • Pyrethroids
  • Organophosphates
  • Carbamates

When applying insecticides, ensure you follow the instructions on the product label. Using too much or too little can be detrimental to the effectiveness of the treatment.

However, be aware that using insecticides can also affect non-target organisms, like beneficial insects and aquatic life. So, consider employing alternative methods like biological control or natural repellents if possible.

Damage Caused by Beetles

Water beetles can cause damage to various household items and structures, particularly carpet beetles and black carpet beetles. Some typical damages caused by these beetles are:

  • Carpet Damage: As their name suggests, carpet beetles eat carpets, especially those made of natural fibers. They can leave behind small, irregular-shaped holes in the material.
  • Wood Damage: Some water beetles can cause damage to wood structures. An example of a wood-destroying water beetle is the powderpost beetle.
  • Infestation: If the water beetles make their way into your home, they can lay eggs in dark, secluded areas like vents, making them difficult to find and remove.

Pro-tip: Keep your home clean and well-ventilated to discourage beetle infestations.

Comparing damage caused by carpet beetles and black carpet beetles:

Carpet Beetles Black Carpet Beetles
Damage to carpets Natural fiber carpets preferred All types of carpets at risk
Damage to wood Rare Some species can damage wood
Infestation sites Vents, carpets, closets, drawers Vents, dark corners, closets

If you suspect a water beetle infestation in your home, it’s essential to address it quickly. Early identification and treatment can prevent severe damages, saving you time and money in the long run2.

Research on Water Beetles

Water beetles are fascinating aquatic insects that play important roles in their ecosystems. Researchers have dedicated time to understanding their biology, behavior, and various species. Let’s dive into a few key aspects of water beetle research.

Adaptations to aquatic life

Water beetles possess fascinating adaptations that allow them to thrive in aquatic environments. For example, some species like the giant water scavenger beetle can grow up to 40 mm in length and have specialized structures called maxillary palps that help them exchange air while underwater. These beetles rise to the surface to make contact with the air, allowing them to replenish their supply of oxygen.

Diversity and species identification

There are many types of water beetles, each with unique characteristics. Researchers use morphological features such as size, color, and hair patterns to identify and classify various species. For example, rain beetles are large, robust, shiny bugs known for their hairy exterior.

Ecological roles

As part of their natural habitats, water beetles serve important ecological roles. They help maintain overall insect populations and act as decomposers, breaking down organic matter in their surrounding environments. However, it’s important to note that some beetle larvae can cause damage to plants, such as apple and pear orchard trees.

In conclusion, water beetle research is important in understanding these insects’ adaptations, diversity, and ecological roles. By studying them, you can gain valuable insights into the complexities and wonders of the aquatic world.


  1. giant water scavenger beetle – Entomology and Nematology Department
  2. Water Beetles as Models in Ecology and Evolution – PubMed

Reader Emails

Over the years, our website, has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – Whirligig Beetles or Apple Bugs

Subject: Sweet smelling water bug
Location: North and South Carolina
August 2, 2012 8:21 am
There is a water bug that skims across the surface of rivers that if you can catch one and smell it’s tummy it smells sweet like strawberries. Do you know what kind of bug this is or why it smells like that? It is tear shaped with tiny legs you can only see when it is flipped over. Also, they always seem to be in groups.
Signature: curios hiker

Whirligig Beetles

Dear curios hiker,
These are Whirligig Beetles in the family Gyrinidae.  We are very intrigued by your description of their smell.  We checked BugGuide‘s family page, but there is no mention of Whirligig Beetles smelling like strawberries, however, in the genus page for
Dineutus, one of four genera in the family recognized by BugGuide, we did find the statement:  “When disturbed, adults produce a defensive secretion that smells like apples.”  There is also mention that another common name is Apple Bug.  This is brand new information for us.  Even though we are quite familiar with Whirligig Beetles and collected them in our youth, we never noticed their odiferous character.  Whirligig Beetles are known for whirling about in circles on the surface of ponds, lakes, calm rivers and calm streams.  BugGuidealso notes that  they “can form rafts of immense numbers on lakes.”

Whirligig Beetle

Thank you!  This is definitely the same insect.  If you happen to come across them again I would suggest smelling their tummies.  Very carefully hold one between thumb and pointer finger and lift the underside to your nose.  Some do tend to give off a stronger scent than others.  Also, they tend to be more odoriferous he sooner you smell them after capture.  I still say they smell more like strawberries than apples.  Perhaps different versions smell different?  Thank you again for your response.  Have a great day!
curious hiker  (the misspelling was driving me crazy  lol)

We thought you were looking for curios in curio shops while hiking.

Lol, thanks for giving me more credit than I deserve.  But, no I just wasn’t paying attention to what I had typed. 🙂

Letter 2 – Water Scavenger Larvae

Aquatic creature
Hi Bug People,
Last year about this time, I was trying to figure out what this creature was, but eventually gave up to get the specimen back to water. Well, here are several more… I am about 50 miles north of Sacramento, California. These were found (plentifully enough) in a creek backwater. They have three pairs of forelegs, mostly move in an inverted position (head down) and are extremely active. I’m guessing it’s the naiad of some insect but, beyond that, I’m stuck. Thanks for your knowledge,
Margaret Stelmok

Hi Margaret,
You have sent in photographs of Water Tigers, the predatory larvae of the Predaceous Diving Beetles in the genus Dytiscus. These fierce predators use their jaws to capture prey, often much larger than themselves, including small fish. Eric Eaton added this correction: ” I am fairly certain the OTHER larvae (multiple, in the jar) are larvae of some kind of water scavenger beetle, family Hydrophilidae. Despite the family name, many are just as predatory as water tigers.”

Letter 3 – Aquatic Beetle Larva

Subject: Green pool bug or shrimp?
Location: Tampa, Florida
April 8, 2016 3:49 pm
We came across this “thing” and what we believe to be 100s, if not 1000s, of what we assume to be it’s babies? Because it looks like them, just really smaller. Thank you for identifying this, hopefully, for us.
Signature: Nicole and Jeff

Aquatic Beetle Larva
Aquatic Beetle Larva

Dear Nicole and Jeff,
This is the larva of an Aquatic Beetle, but there is not enough detail for us to be more specific.

Letter 4 – Aquatic Beetle Larva

Subject: what is this?
Location: Preston county West virginia
June 30, 2017 5:29 pm
I found this while cleaning my pool. Could you please tell me what it is. The pool was drained to clean leaves at the bottom left from the fall.
Signature: not in my pool

Aquatic Beetle Larva

The best we can do is identify this as the aquatic larva of a Water Beetle.

Letter 5 – Giant Black Water Beetle

Shiny Olive-green 3-inch…Beetle?
July 23, 2009
I did not kill this bug!! He was lying on our bumper when we got out of our car at the New York Aquarium in Brooklyn, New York (right by the water on Coney Island). We had driven up from the Washington, DC, area that day and I’m not sure how long he was on board. He was about three inches long and a shiny olive color. If you could just get me started I’m sure I could find him, but all my searches turn up metallic looking bugs, which he was not. Thanks you!!
Brooklyn, NY, USA

Giant Black Water Beetle
Giant Black Water Beetle

Hi Hawke,
This is some species of Water Beetle, either a Water Scavenger in the family Hydrophilidae, or a Predaceous Diving Beetle in the family Dytiscidae.
According to BugGuide:  “Water scavengers have keeled sternum, come up for air head first. Diving beetles have unkeeled sternum, come up for air tail first.”  We are inclined to ID this as the Water Scavenger, Hydrophilus triangularis, which BugGuide describes as:  “Large, shiny black with olive tinge. Underside with prominent spine (prosternal process). Similar to the usually smaller H. (Dibolocelus) ovatus. H. triangluaris is more oblong, H. ovatus more oval. H. ovatus is more common southward.”  The common name is the Giant Black Water Beetle.

Confirmation from Eric Eaton
The giant black water beetle is indeed Hydrophilus triangularis.

Found this picture which sure looks like him.
Thanks!  I was stumped.
My husband says he saved him to put by the computer…  if he is intact I’ll try to take a better picture.  He was quite an impressive creature and I didn’t see any others on What’s That Bug.

Letter 6 – Whirligig Beetles

Subject:  Skimming around on the edge of my pond
Geographic location of the bug:  Tampa, Fl.
Date: 11/29/2017
Time: 03:11 PM EDT
Found these guys zooming around our pond. Tried to get closer for a shot but they zip off.
How you want your letter signed:  Curiously

Whirligig Beetles

These are Whirligig Beetles in the family Gyrinidae.  Of the genus DineutusBugGuide states: “Found on the surface of streams/rivers, ponds, lakes (can form rafts of immense numbers on lakes).” 


  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. is his passion project and it has helped millions of readers identify the bug that has been bugging them for over two decades. You can reach out to him through our Contact Page.

    View all posts
  • Piyushi Dhir

    Piyushi is a nature lover, blogger and traveler at heart. She lives in beautiful Canada with her family. Piyushi is an animal lover and loves to write about all creatures.

    View all posts
Tags: Water Beetles

Related Posts

12 Comments. Leave new

  • Wow! So they smell like food as a defense to not get eaten!

  • I have noticed the smell since childhood, but I always described it as fruit punch.

    I guess not many people sniff beetles.

    • Hi Sherry,
      Though we were very familiar with Whirligig Beetles from a very young age, we must confess that we never smelled them. Next time we will make it a point to do so.

  • I have noticed the smell since childhood, but I always described it as fruit punch.

    I guess not many people sniff beetles.

  • I should note that my beetles were from Alabama. Maybe there are regional differences in whirligig fruit bouquet, lol.

  • The ones in Kansas smell like Jolly Rancher Green Apple

  • They smell like apples because they’re releasing cyanide (one compound in apples) we always describe the smell as “apple jacks” as there is also a cinnamon and oat smell along with the apple smell.
    The cyanide makes them taste bitter and unpleasant to predators

  • They smell like apples because they’re releasing cyanide (one compound in apples) we always describe the smell as “apple jacks” as there is also a cinnamon and oat smell along with the apple smell.
    The cyanide makes them taste bitter and unpleasant to predators

  • In southeast Alabama (half a century ago), I heard them referred to as “mellow bugs.”

  • We called them cider bugs when I was growing up! Had them in our pond in Indiana.


Leave a Reply

Your email address will not be published. Required fields are marked *

Fill out this field
Fill out this field
Please enter a valid email address.
You need to agree with the terms to proceed