Water Scorpion vs Fish: Intriguing Aquatic Battles Explored

Water scorpions and fish are fascinating aquatic animals that you might encounter in your local ponds or streams. As you delve into their unique behaviors and adaptations, you’ll discover intriguing aspects of their lives in the underwater world.

In the realm of water scorpions, these insects are equipped with long, slender breathing tubes that allow them to extract oxygen from the water’s surface. Fish, on the other hand, possess gills that enable them to extract oxygen from the water itself. This difference in respiration techniques highlights the amazing variety found in aquatic life.

As you continue to explore the topic, you’ll find many interesting comparisons between water scorpions and fish. For example, water scorpions are skilled predators that use their front legs to grasp prey, while fish generally rely on speed and agility to catch their meals. By investigating these fascinating creatures further, you’ll certainly gain a deeper appreciation for the diversity and adaptability of life underwater.

Understanding Water Scorpions


Water scorpions are fascinating aquatic invertebrates that belong to the family Nepidae. They have a unique appearance often resembling underwater walking sticks or needle bugs. These creatures can be found in various parts of North America.

Although they are called water scorpions, they are not closely related to true scorpions. Instead, they belong to the Hemiptera order, making them more similar to water bugs. Their body is characterized by a flattened, elongated oval shape with three pairs of jointed legs.

Habits and Traits

Water scorpions are known for their incredible ability to breathe underwater through a long, needle-like siphon at the tip of their abdomen. They use this siphon to extract oxygen from the water, allowing them to stay submerged for extended periods.

They are crawlers rather than swimmers, moving slowly through the mud at the bottom of ponds, streams, and other bodies of water. Their flattened body shape allows them to be well-camouflaged and to hide from potential predators.

Hunting Strategy

These aquatic invertebrates are ambush predators that rely on stealth and patience to capture their prey. Some of their favorite foods include:

  • Small fish
  • Invertebrates
  • Tadpoles

Their hunting strategy involves blending in with their surroundings and waiting for an unsuspecting victim to come close. When the prey is within reach, they strike quickly using their sharp, raptorial forelegs to seize it.

Home Science

Water scorpions lay their eggs on underwater plants near the water surface. Before hatching, the eggs absorb oxygen from the water. After hatching, the nymphs go through five stages of development, called instars, before reaching adulthood.

Water scorpions provide a valuable service to their ecosystem by helping to control populations of other aquatic invertebrates. By preying on these organisms, they contribute to the overall health and balance of the water bodies they inhabit.


The family Nepidae comprises two genera:

  • Nepa
  • Ranatra

Within these genera, there are various species of water scorpions, each with their distinct features and characteristics. It’s important to understand the taxonomy of these fascinating creatures to appreciate the diversity within their family.

In summary, water scorpions are incredible aquatic invertebrates known for their unique appearance, habits, and hunting strategy. As part of the diverse ecosystem, they play a crucial role in controlling populations of other aquatic organisms and maintaining the health of their habitats.

Getting to Know Fish

Understanding Family Scorpaenidae

The Family Scorpaenidae is a group of fish that includes some fascinating members like scorpionfish, lionfish, rockfish, and stonefish. These vertebrates live primarily in tropical waters and are known for their unique appearances and impressive survival skills.


Scorpaenidae fish have certain characteristics that set them apart from other fish:

  • Mottled and often vibrant coloration to blend in with their surroundings
  • Spines and venom glands on their dorsal fins for defense
  • Wide, fan-like pectoral fins for stability and swimming

For example, lionfish are known for their striking colors and long, venomous spines.

Hunting and Feeding

Scorpaenid fish rely on their camouflage and sedentary lifestyle to hunt and feed. They often hide in the rocky areas or coral reefs, sneaking up on small fish and crustaceans before swallowing them whole. Some examples of their prey include mollusks and other invertebrates.


These fish are typically found in tropical waters around the world. Some are known to be invasive species, like the lionfish from the Pterois genus, which have become a problem along the Pacific Coast of the United States.

Danger to Humans

While not all Scorpaenidae fish pose a danger to humans, a few can deliver painful and sometimes fatal bites through their venomous spines. These fish should be approached with caution, especially if you are unsure of the species. Stonefish, for example, are considered one of the most venomous fish in the world, so watch your step when exploring any habitats where they might live.

Comparative Analysis

Water Scorpion:

  • Scientific name: Ranatra
  • Insect belonging to the Nepidae family
  • Snorkel-like breathing tube


  • Belongs to a diverse group of aquatic animals
  • Exists in various sizes and shapes

In this comparative analysis, we will look at some of the unique features and characteristics of water scorpions and fish.

Characteristic Water Scorpion Fish
Status Insect Aquatic Animal
Description Resembles a scorpion with long skinny legs Comes in various shapes and sizes

Water scorpions have a snorkel-like breathing tube called a siphon, which they use to breathe when submerged underwater. On the other hand, fish have specialized organs called gills that help them extract oxygen from the water and remove carbon dioxide.

When it comes to locomotion, water scorpion uses its legs to swim or crawl, while fish typically use their fins for swimming. Fish display a wide range of body shapes and sizes, allowing them to inhabit various niches in water environments. On the other hand, water scorpions, belonging to the Ranatra genus, have a distinct body shape that closely resembles a stretched-out scorpion.

The diet of water scorpions primarily consists of other insects and small aquatic creatures. Using their sharp front legs, they capture their prey and inject a venomous substance to subdue it. In contrast, fish consume a wide range of food sources, including algae, plant material, insects, and smaller fish, depending on the species.

Pros and Cons

  • Water Scorpion

    • Pros: Intriguing appearance; fascinating hunting method
    • Cons: Limited habitat; smaller food source range
  • Fish

    • Pros: Diverse species; adaptable to various environments
    • Cons: Require specific water quality and temperature conditions

In this brief comparative analysis, you can see that water scorpions and fish possess unique characteristics that differentiate them in terms of appearance, adaptation, and their ecological role in aquatic environments.

Reader Emails

Over the years, our website, whatsthatbug.com 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 – Water Scorpion found in Guppy Tank!!!


Type of bug needs I.D.
January 9, 2010
Just found this bug with an aquarium order I received this week. Found it in a tank with some guppies. I really have no idea what it is or how it came to be. I would appreciate it if you could identify it.

Water Scorpion
Water Scorpion

Hi Scott,
This is a Water Scorpion in the genus Ranatra and there is information on BugGuide.  Water Scorpions are predatory True Bugs and they will eat the guppies, so you should not keep it in the tank.  Prey is captured in the raptorial front legs and the sucking mouthparts will drain the prey of its fluids.  The Water Scorpion may have been introduced on plants.  Water Scorpions, like many other aquatic insects, can make interesting pets, but as they can fly, you should keep the tank covered.  Interestingly, we have a section in the book manuscript we are writing entitled “What’s That in the Aquarium” that is devoted to aquatic insects sometimes encountered by the aquarist.

Letter 2 – Aquatic Mites on Water Scorpion


What’s ON that bug? Ranatra w/ orange bumps
Thu, Jul 2, 2009 at 3:12 PM
I recently tracked down the ID of this odd insect in a local pond as a Water Scorpion (Ranatra spp.), but all of the individuals I’ve seen so far are covered in strange, orange bumps that do not appear to be “normal” or common. Do you have any idea what these might be caused by? The pond is next to the building I work in and appears to be the result of dam work by the local beaver’s union. There is plenty of food for these guys with damsel flies, tadpoles in the thousands and other small, crunchy things. The other wildlife in the area does not appear to be suffering from any apparent disease or sicknesses and the vegetation around the pond appears to be thriving.
Eric Snyder
Issaquah, WA 98027

Water Scorpion with Phoretic Mites
Water Scorpion with Phoretic Mites

Hi Eric,
Congratulations on identifying the Water Scorpion in the genus Ranatra.  That is not an easy identification.  The orange bumps are Aquatic Mites.  The Aquatic Mites often use flying aquatic insects to get from one body of water to another, a behavior known a phoresy.  Some time back when we posted an image of a ToeBiter with mites, we got this comment from a reader.

Previous Comment on similar posting:  Mites on the toe-biter?
Hi Daniel and Lisa Anne,
About the email on the Toe Biter from Tom on (01/27/2007) who talks about having 12 red mites on his Toe Biter? I remember seeing mites on aquatic insects, looking suspicious, and so I looked it up, and it turns out that *all* of the more than 5,000 known species of aquatic mites (Hydracarina) are partly parasitic. When they are larvae, aquatic mites are parasitic on aquatic insects, but as adults the mites become free-swimming and predatory. Winged aquatic insects, such as the toe biters, fly around of course, and that way the mites are spread from one body of water to another. You can read a lot more interesting stuff about them at:
And at :
Best to you as always,
Susan J. Hewitt

Letter 3 – Water Scorpion


Good morning!
Hi there. This fellow was extricated from underwater brush in a lake nearby which is mostly frozen over though thawed in places. At first I believed he was a "Walking Stick." However, the legs seemed wrong. Scanning internet images led me to now believe he may be a Water Scorpion. (And to think I kept repositioning him, which he seemed to tolerate cheerfully enough!) I’d really like your confirmation, please! Thanks for your tremendous site!
Michelle Mahood
Shingletown, California

Hi Michelle,
We always enjoy getting interesting images from you. Yours is the first photograph we have gotten of a Water Scorpion, though we have gotten several letters. Your specimen looks like a Western Water Scorpion, Ranatra brevicollis. They get to be about 1 inch long with an additional inch of breathing tubes. They are found in shallow ponds amid debris. They will bite painfully if provoked.

Letter 4 – Second Water Scorpion photo today


Water Scorpion
I had a chain of toad eggs in my "cement pond" and there were a family of these bugs congregated around them. (It seemed some had eggs in their pinchers!) I looked at your sight and found them to be water scorpions. One was about 4 inches long so I put it aside for a photo session. My question is, "Do these guys eat toad eggs?"

Hi Katherine,
This is the second image of a Water Scorpion in the genus Ranatra we received today. The first was from Georgia and yours is from parts unknown. We believe that Water Scorpions might prefer moving prey, but your observation indicates that they may eat toad eggs.

Letter 5 – Chinese Water Scorpion


Water Scorpion, Toe Biter
Hi, I currently live in China and found this guy. Thanks to your site I think I’ve indentified him as a toe biter, but thought you might like the photo. The body was around 3", not including the snorkel, tail thing.
Jeremy Daum, Kunming, Yunnan, China

Hi Jeremy,
This is a Water Scorpion in the genus Nepa. Thanks for sending us your photo.

Letter 6 – Water Measurer from England


Subject: Stick insect like thing
Location: Pond, England, Surrey ,Guildford
April 25, 2015 2:25 am
I was wondering if you could help me with a discovery that I found in my pond. I was clearing out duck weed when I found what I can only describe as a stick insect running across the water. It is about 2cm long and it has 6 legs and 2 antennae on a long thin body.
I have searched lots and lots of websites but I still cannot find out what it is.
Signature: From katie wright age 12

Water Scorpion
Water Strider or Water Scorpion???

Dear Katie,
This is a predatory, aquatic True Bug, and at first we thought it was in the family Nepidae whose members are commonly called Water Scorpions as they will deliver a painful, though not dangerous bite if they are carelessly handled.  When we reread your submission, we realized you stated it was  “running across the water.”  We apologize for the error, but since it was on top of the water, it is more likely a Water Strider in the family Gerridae.  We wish your images had greater detail.

Correction:  Water Measurer
Thanks to a comment we received, we now know that this is a Water Measurer in the family Hydrometridae and we learned on BugGuide that they are found “on emergent/floating vegetation along edges of ponds, marshes, and pools of slow-moving streams”
and that they feed upon “newly emerged, slow-moving, dying, or dead invertebrates (midges, mosquito larvae, bloodworms, ostracods, springtails, etc.)”  BioImages UK has some nice images.

Thank you sooooooo much I am really really pleased that you found out what it was. I can’t believe how good you were at identifying. If someone ever poses a question like that to me I will definately recommend you. I will ask my mum if I can make a donation


  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. whatsthatbug.com 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.

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  • 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.

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10 thoughts on “Water Scorpion vs Fish: Intriguing Aquatic Battles Explored”

  1. ive been cleaning out my pond and have found some weird bugs i know one is a water scorpion and there are lots of toe biters i have one with eggs on its back but i have two im not sure what they are i can send pictures of them all so yo can add to your collection if you give me a email.
    and hopefully you can tell me what the two are that im not sure about.

  2. Like the lady in Muswellbrook I found what I now know to be a water scorpion swimming in our pool, unlike the lady I scooped it out of the pool with my bare hand unawares that it could bite, it differed in that the nippers and legs were quite small and the body fatter and longer compared to the Muswellbrook specimen and about 10cm in length, I left it on the side of the pool and ran for a camera but unfortunately it had gone before I returned.
    M. Mansell South Coast Illawarra N.S.W.

  3. Hi guys, I can certainly see the resemblance to Gerridae and Nepidae, but I believe that this is more than likely a Hydrometridae more commonly called the water-measurers. The length of the head, positioning and length of the antennae, and position of the eyes at the sides like that give it away. They’re definitely cool little guys, and that’s a great picture!

  4. Hi there, I am finding lots of these bugs in my salt water swimming pool. How can I get rid of them? Do they bite?
    Regards Donna

    • Water Scorpions are so named because of the painful bite received by waders and swimmers in lakes and ponds who accidentally encounter them. We do not provide extermination advice.

  5. Hi there, I am finding lots of these bugs in my salt water swimming pool. How can I get rid of them? Do they bite?
    Regards Donna


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