Water tigers are quite famous for their large appetites and ruthless hunting abilities. But what do water tigers turn into when they grow up? Do they remain as voracious? Let’s find out.
When you find a new type of larva in your pool or backyard pond, it’s natural to wonder what it’s going to grow into and whether you should be concerned.
While water tigers are relatively harmless to us, you might be worried about them pupating into a dangerous or troublesome pest species.
Well, let’s dive in and find out what water tigers turn into.
What Do Water Tigers Become?
Water tigers are the larvae of a beetle species known as the predaceous diving beetle. Their elongated bodies have long and thin legs that they use to swim and move around underwater.
Usually, the rear end of a water tiger floats on the surface while the remaining body remains suspended upside down.
Even in the larval stage of their life cycle, these insects are deadly predators. They suck out the juices of their prey using hollow pincers while grasping them within their powerful jaws.
They are voracious eaters and love to eat anything they can get their jaws on. They lurk around in the water, lying perfectly still, and attack when the prey least expects it.
Here’s a video of a water tiger attacking prey. Watch it to understand why they are so feared!
https://youtu.be/OXfr0oFq05s
Predaceous Diving Beetles
This bug can grow between 1 to 1.5 inches long. You can find it in myriad colors, be it black, dark green, or olive, and it often has golden or other highlights.
Like many aquatic bugs, they have streamlined body that helps them move smoothly through the water.
Unique Features
Although they are aquatic insects, predaceous water beetles are capable of flying too.
Underneath the upper pair of hard, shield-like wings known as the elytra, you can find another set of membranous wings.
The rear legs have a thick fringe of hairs that help them swim.
These bugs also possess short and powerful jaws with hollow teeth to bite their prey and inject enzymes that digest the prey from the inside out.
Lifecycle
These diving beetles usually lay eggs on the leaves of aquatic plants, often by piercing into the stem.
The water tigers later hatch from these eggs and spend their larval stage in the water.
Once ready to pupate, they move out of the water and burrow themselves into the soil. Upon completing pupation, adult predaceous water beetles emerge.
The adult beetles live near or around water ponds and other sources of water and can also remain underwater for a long time.
Habitat
Most of their life is spent in water, except for the pupal stage. They even lay eggs in water amidst the aquatic vegetation.
You will mostly find them in calm waters at the edge of ponds amidst weeds.
You may also come across predaceous water beetles in swimming pools and birdbaths, especially if there are electric lights to lure them.
How Do They Survive Underwater?
Water tigers breathe underwater using spores near their abdomen, known as spiracles.
Adult beetles use the same spiracles to store oxygen so that they can breathe underwater, but their spiracles are under the elytra (wings).
However, the adults also need to breathe on land, so they don’t actually breathe underwater; they just use the spiracles to store oxygen.
Their respiratory system is quite complex and requires regular care. From time to time, they follow a process called secretion grooming to keep this critical system functioning properly.
In this process, they secrete a substance from their pygidial gland, which helps kill any harmful microbes in their spiracles.
By trapping air between their wings and body, they can carry extra breathable air while diving and stay underwater for longer.
Some sources suggest they can stay submerged for more than a day! During the winter season, both the adult diving beetle and water tigers can be found under the ice.
What Do Water Tigers Eat?
One of the most notable details about water tigers is their feeding habit.
They earned their name from the fact that they are voracious eaters and powerful aquatic predators that even hunt prey larger than themselves.
Potential prey for water tigers in the wild include larvae of other insects, tadpoles, and even small fish.
Water tigers hunt by cautiously approaching their prey with their jaws wide open and snapping forward to seize them.
Grasping the prey in its jaws, the water tiger injects it with powerful digestive enzymes. The enzyme liquefies the prey from the inside out, and the larvae feed on this liquified food.
Water tigers can even hunt without eating the prey; if they see another attractive prey nearby, they will leave the other victim’s carcass lying around and go for the second hunt.
Despite being fierce predators, water tigers also have their own predators – such as fish, skunks, and raccoons.
Frequently Asked Questions
Are water tigers harmful?
Water tigers aren’t harmful to humans and usually keep to themselves. They might bite you if disturbed but won’t cause much pain or get you sick.
However, a large number of water tigers in your swimming pool might pose a problem.
Do water tigers bite?
Yes, water tigers have powerful jaws and can bite you if you get too close.
However, their bites aren’t painful to humans or spread any diseases. The same goes for the adult diving beetles too, but their jaws are more powerful, and the bites can sometimes draw blood.
Why is it called Water Tiger?
The larvae of the predaceous water beetle are called water tigers due to their voracious appetite and the way they hunt any available prey, even those larger than themselves.
As mentioned earlier, water tigers hunt a variety of aquatic organisms, including fish and tadpoles.
Where do water tigers live?
Water tigers mostly live on the edges of water bodies and prefer brackish water, which is why they are much more common in ponds than in swimming pools.
However, if the water in your swimming pool gets too dirty, it might attract these larval pests.
Wrapping Up
Water tigers and predaceous water beetles are mostly harmless; there’s nothing to worry about for humans. Some people even keep these diving beetles as pets.
However, if you find several of them in your swimming pool, it probably needs some shock chlorination to get rid of them.
Lastly, having them in your pond isn’t a bad thing as they can help eliminate mosquitoes by feeding on their larvae.
Thank you for reading; we hope you enjoyed this information!
Reader Emails
Water tigers are amazingly fascinating creatures, and over the years, many of our readers have shared their experiences with them and their adult forms, the diving beetles.
Read the mails below to get a flavor of how many of our readers have been keeping water tigers in their ponds and even as pets!
Letter 1 – Water Tiger and Tadpole
Hi Bugman,
I love the site, but I’ve not been able to find this in the alphabetic list or with the search – can you help at all please ? When I saw them I assumed they were dragonfly larvae, but now I’ve had a chance to look up the identification I don’t think they are – several points don’t match. There were 3 of them, in a small seasonal pond in South-West Scotland this morning – busily eating the tadpoles. I’ve not seen them before, and unless they’re something interesting I’m tempted to beat them to death before they finish off the last of the taddies. I was there about 4 weeks ago (and so were the tadpoles), and I visited at least once a month all through last year, plus I have a decent pond in my garden with frogs, toads, several newts (endangered here), and plenty of insect life, but I’ve never seen anything like these monsters. They were about 30mm long when they straightened out, which was only when they were swimming (they swim by moving their legs, rather than “jet propulsion”). They sat still in the arched pose in the photo’s until a tadpole came past, then latched onto it and killed it with their pincers. In the photo’s the pincers look a bit like feelers, but in reality they were curved, hard and obviously sharp killing instruments. There are all sorts of pond-skaters, water-boatmen, and general creepy-crawlies in the pond, but these 3 were a lot bigger than anything else, and only interested in killing tadpoles. They seem to have 6 legs, which might be some help, and a couple of small “spikes” on the tail (no gills). The light was terrible for photography, but they were basically green with slightly brown heads. We’ve had dragonfly, damsels, cranes, midges, and just about everything else that flies on the site (bats are my “thing”, and we’ve got those as well), and we’ve also got frogs, toads, a possible newt, lizards, slow-worm, mice, owls, a fox, and deer (which do a lot of damage to the trees if we don’t keep on top of them). We do like nature, in all it’s forms, but the rate these things were eating the tadpoles was quite alarming, so unless they’re something interesting I’ll have to either splat them or at least section off one part of the pond, or we’ll have no tadpoles left. Hope you can help.
Thanks,
Kev.
Hi Kev,
What a wonderful letter. We just posted another photo of a Water Tiger from Northern California. These are the predatory larvae of the Predaceous Diving Beetles in the genus Dytiscus, and they have a voracious appetite. Eric Eaton wrote in with this addition: “I agree the one with the tadpole is a dytiscid, but I’d be hesitant to assign a genus to it. I really think anyone is doing great just getting immatures (and usually adults, too) to the family level! Nice work.”
Letter 2 – Water Tiger
Hello Bugman,
I was at Lake Dorathy in Kirkland Lake, Ontario, swimming with some friends when this bug floated by and we grabbed it with the insect net. When I went touch it, it pinched me with it’s pincers, which are extremely sharp! It’s got a stinger like tail, and it resembles a shrimp in the body. I asked the folks that have been there for over 20 years and they had no idea. They think it may be some form of Larvae or nymph. If you could let me know what this thing is that would be wonderful. I’ve attached some pictures, hopefully they’ll help. Thanks!
Dan
Hi Dan,
This is a Water Tiger, the larva of the Predaceous Diving Beetle. Looks like it caught a minnow.
Letter 3 – Water Tiger
We were berry picking and my daughter found this insect in a mud puddle.Could you tell me the name of this insect,thanks.
Rhonda
Hi Rhonda,
This is the predatory larva of a Water Beetle, either a Giant Water Scavenger, or, more likely, a Predaceous Diving Beetle in the family Dytiscidae. These larvae are sometimes called Water Tigers.
Letter 4 – Water Tiger
Wed, Nov 5, 2008 at 9:43 AM
I found this freshwater invertebate in July of 2008. I found it in a culvert located in the Chippewa National Forest, north of Cass Lake, MN. It is about 1.5 – 2 inches long.
What is this invertebrate?
North Central Minnesota. North of Cass Lake, MN.
Dear Reader,
We have always called the larvae of Predatory Water Beetles by the colorful name Water Tigers. We believe your larva is of a Giant Water Scavenger Beetle in the genus Hydrophilus.
Letter 5 – Water Tiger
Wed, May 20, 2009 at 3:35 PM
My children, husband and I are avid nature lovers. One May night at the local ballpark my children showed my husband a drying up “creek” bed with hundreds of tadpoles and frog eggs in it. My daughter and I had already been performing tadpole rescue on a water catch next to our drvieway that day. Needless to say the next day the kids and I went to rescue those tadpoles. While driving my son said the worm in his container was freaking him out. I thought he was talking about the tadpoles. When I began pouring them into their new home this worm took off chewing through the eggs. I quickly scooped it out. We watched it and noticed that it has six legs, large pincers, and appears to breathe through an orifice in its tail. I thought it might be a juvenile dragonfly, I checked your site (which we use frequently) and have found noth ing like it. Thanks for your help.
Jodie
Atlanta, TX
Dear Jodie,
It was in our budding fascination with aquaria in our youth that we first heard the name Water Tiger to describe the larvae of the Predacious Water Beetles in the genus Dytiscus, though according to BugGuide, Predacious Water Beetle and Water Tiger apply to the entire family Dytiscidae. Here is what William T. Innes wrote in 1935 in Exotic Aquarium Fishes: “Water Tiger This sleek, spindle-shaped creature is the larval form of a large Water Beetle (Dytiscus), which itself is also a powerful enemy of fishes. There are several species, but in effect, as far as the aquarist is concerned, they are all one. … The pincers, or mandibles, are hollow, and through these they rapidly suck the blood of their victims. Growth is rapid and they soon attain a size where they attack tadpoles, fishes or any living thing into which they can bury their strong bloodsuckers. Theirs is one of those appetites which ‘grows by what it feeds upon,’ and they move steadily from victim to victim. … What helps make these larvae so deadly is that they are good swimmers. … The Water Tiger breathes air through its rear end and, therefore, must occasionally come to the surface.”
Letter 6 – Water Scavenger Beetle Larva
Location: Pak Chong, Thailand
October 25, 2010 10:20 am
Hi. This thing is swimming in our pond in Pak Chong, Thailand, a mountain/jungle region in North Eastern Thailand. It’s several centimeters long, and seems to have 6 legs that it uses to swim. Hangs out both under water and on the surface. Not sure if it’s some type of dragonfly nymph? Any ideas? Thanks.
Signature: macnmotion
Dear macnmotion,
This is the larva of a Diving Beetle, most probably a Predaceous Diving Beetle. They are sometimes called Water Tigers.
Thank you for the very quick reply. So the ones in our pond look much younger and less developed than some of the photos I’m seeing. I guess I can expect changes to be upcoming.
Will this larva begin to eat the small fish in the pond (1 cm)? So far these things hang out near the light at night and have made no move to attack any fish as far as I have seen.
Thanks. Andy
Hi again Andy,
Water Tigers will eat small fish.
Letter 7 – Water Tiger
Location: PEI
July 23, 2011 2:08 pm
We found this bug in a puddle, in the country, on Prince Edward Island,Canada.
Signature: Josh
weird bug came out of a puddle.
Location: Prince Edward Island, Canada
July 24, 2011 9:53 am
We were walking in the back fields the other day and this thing came scurrying out of a puddle. We slowed him down long enough to snap a pic. No one around here has ever seen one.
Signature: Josh
Hi Josh,
Thanks for resending your identification request. We had actually opened your email yesterday and we had plans to post your request, but somehow time got away from us and we forgot about it. This is a Water Tiger, the larva of a Predaceous Diving Beetle in the genus Dytiscus. You can see numerous examples on bugGuide. Water Tigers are fierce hunters and they are capable of catching and feeding upon tadpoles and small fish.
Hi, thanks for the reply, and information. I apologize for sending it twice, i sent it from a new mobile phone and thought the first one did not go through. It’s amazing how many interesting creatures there are.
Thank you very much for your time,
Josh
Letter 8 – Water Tiger
Location: Beaverton, Oregon
March 22, 2013 8:17 pm
My son and I found this bug in a vernal pool. I cannot figure out what it is, but I hope never to meet one in a dark alley at night. I have two pictures, one of the whole bug and one through a microscope that shows its formidable mandibles. We would be most grateful to know more about it.
Many thanks,
Laura
Signature: Laura B
Hi Laura,
This is the larva of an Aquatic Beetle, and we believe it is the larva of a Predaceous Diving Beetle in the family Dytiscidae. Here is a photo from BugGuide that looks very similar. We are sorry but we do not have the necessary skills to identify this to the species level. We remember these larvae being called Water Tigers in an old aquarium book by Innes.
Daniel,
Thank you! You are clearly the Patron Saint of creepy-crawlies and those who appreciate them!
With deepest admiration,
Laura
Letter 9 – Larva of a Predaceous Diving Beetle
Location: Florida
June 8, 2014 3:24 pm
What is it?
Signature: bigchew
Dear bigchew,
You didn’t indicate where you found this large beetle larva, and we are guessing it came from some aquatic environment because it looks like the larva of a Predaceous Diving Beetle, sometimes called a Water Tiger. You can compare your image to this image on BugGuide.
Letter 10 – Water Tiger
Location: Northern MN (Grand Rapids)
July 8, 2014 7:06 pm
I have no idea what this is. I live in northern mn, I’m originally from Texas, in saying this all the locals have never seen it either. My friend found it crawling across the parking lot of our church.
Signature: doesn’t matter
Dear doesn’t matter,
This is an aquatic Water Tiger, the predatory larva of a Predaceous Diving Beetle, and we cannot fathom why it was in your church parking lot. Perhaps one of Minnesota’s 1000 lakes is adjacent to the parking lot. Perhaps someone captured it in a nearby lake and left it in the parking lot.
Letter 11 – Bug of the Month April 2015: Water Tiger AKA Giant Water Scavenger Beetle Larva
Location: Mississippi River, central Louisiana
March 28, 2015 5:14 pm
Don’t go near the water! Found this thing in the Bayou of central Louisiana at the end of March. My research has turned up some similar creepy crawlies but nothing quite the same. What is it?
Signature: Boatswain
Dear Boatswain,
We absolutely love your colorful description of what we originally thought was a Water Tiger, the aquatic larva of a Predaceous Diving Beetle in the family Dytiscidae, but once we searched BugGuide and compared your individual to images of larvae of Giant Water Scavenger Beetles in the family Hydrophilidae, we determined that was the correct identification for your creature. According to BugGuide contributor Andrew Tluczek: “I have a masters in Entomology and have worked with aquatic insects. It is a Hydrophilidae. The mandibles have ‘teeth’ which Dytiscidae larvae do not have.” Your individual has “teeth” on the mandibles, and other research turned up additional physical similarities. According to the University of Wisconsin at Milwaukee Field Station site: “WSB [Water Scavenger Beetles] larvae are described as ‘sluggish’ and are found crawling on the pond floor or climbing on underwater vegetation. The larvae is a ‘couch-potato’ version of the sleek PDB [Predaceous Diving Beetle] larvae/ water tigers (pictured) (they sometimes share the ‘water tiger’ moniker). WSB larvae often have paired, gill-like structures protruding from the sides of their abdomens. Their feeding category is ‘engulfer-predator;’ they use their hollow jaws to suck out the juices of their prey. Their food-list includes their brethren; they love mosquito larvae but will go after mini-fish and so are an unwelcome addition to a koi pond. Larvae back their abdomen up to the water’s surface and take in air through spiracles (pores) at its tip. They spend a month underwater as larvae and about 12 days pupating in a cell in moist soil.” That information thrilled us as we can now safely use the term Water Tiger to describe the larvae of aquatic beetles in both families. According to Bugwood: “Larvae, which occur in water, have an elongate body and large dark head with prominent curved jaws. Elongated spiracles through which they acquire oxygen arise from the end of the abdomen. … The immature stage is a predator, working by ambush to lie in wait, seizing and crushing prey that comes within reach. Most of their diet is made up of small insects and other aquatic invertebrates. However, their jaws are quite powerful allowing them to consume snails whole as well as catch large prey such as tadpoles and small fish.” A Mosquito Tumbler, the pupa of a Mosquito, is visible in two of your images. We have selected your submission as our Bug of the Month for April 2015.
Letter 12 – Predaceous Diving Beetle Larva
Location: San Isabel national forest, Colorado
August 18, 2015 4:13 pm
I found this critter in a unnamed lake at about 12,000 ft. There was only this creature, leaches and small invertabreas that looked like minnows. Under closer inspection they were not minnows but a small swimming animal using cilia to move. I have found pictures close to this mystery animal but nothing exact. Also, was wondering if there may be a guess at what the smaller swimming creatures were too, (sorry blurry pic).
Signature: Adam
Dear Adam,
This magnificent aquatic predator is a Water Tiger, a Predaceous Diving Beetle larva, probably in the genus Dystycus based on this BugGuide image. According to BugGuide, they can be identified by the following features: “Larvae with prominent cerci and dense lateral fringes of hair on the last 2 abdominal segments and cerci. The anterior portion of the head is rounded.” We cannot make out anything in your blurry image, but we suspect the “small swimming animal using cilia to move” is a Fairy Shrimp.
Letter 13 – Water Tiger
Location: Minot, ME
June 4, 2016 3:18 pm
Hello!
Our five year old son was recently catching frogs in the pond at our house and was “bit” by this strange bug. We then noticed that the pond was full of them. They have six legs, are aggressive, swim, also walk on land, two pinchers on the head as well as two small pinchers on the tail.
Signature: Colbath Family
Dear Colbath Family,
This is a Water Tiger, a common name for the larva of the Predaceous Diving Beetles in the family Dytiscidae, and it is most likely in the genus Dytiscus, based on this BugGuide image.
Letter 14 – Water Tiger
Location: Northern wisconsin forest (grass)
July 16, 2016 1:41 pm
Hello bugman, my name is jacob, and i found a bug in northern wisconsin that i cant identify. Date is july 15. Translucent head, six legs, large pincers, and maybe a stinger? Found at 2pm. Thanks
Signature: Jacob
Dear Jacob,
This is a Water Tiger, the predatory aquatic larva of a Predaceous Diving Beetle. Since they are aquatic, we don’t understand why you found it on grass in a forest. See BugGuide for verification of our ID.
Letter 15 – Water Tiger and Tadpoles
Location: Gloucester County New Jersey, USA
August 2, 2017 8:17 pm
I have standing water on my property that is there from rain, not spring feed, today while looking at the water, I noticed these flat brownish insects in the water, I don’t remember seeing these bugs before, I thought they might be leeches but every picture I googled of leeches showed them being black. Also these bugs have pitchers, please help, thank you,
Signature: D. Clement
Dear D. Clement,
This appears to be a predatory larva of an aquatic beetle, commonly called a Water Tiger. It is surrounded by Tadpoles, and they are most likely its prey.
Letter 16 – Water Tiger from France
Geographic location of the bug: Burgundy france
Date: 06/08/2018
Time: 01:05 PM EDT
Your letter to the bugman: This bug had large pincers at the front, legs on his front half and moved like someone dancing the worm. It was about an inch long and very aggressive. If provoked it would curl up back on itself.
How you want your letter signed: C. McCarthy
Dear C. McCarthy
Was it found near or in water? It looks to us like an aquatic beetle larva, commonly called a Water Tiger.
Hi Daniel,
Yes, it was near a small pond. Thanks for the quick positive identification, it helped solve a little debate with the family 
Chris
Letter 17 – Water Tiger
Geographic location of the bug: Wilmington, NC
Date: 08/08/2018
Time: 01:34 AM EDT
Your letter to the bugman: I found this in my ditch after a bunch of rainfall. We have had standing water for 2 weeks. It has 6 legs near its head.
How you want your letter signed: Wendy Pendill
Dear Wendy,
This looks to us like a Water Tiger, the larva of a Giant Water Scavenger Beetle, which is also pictured on BugGuide. According to BugGuide: “Larvae often predatory.” Here is a nice BugGuide posting.
Letter 18 – Water Tiger
Geographic location of the bug: West central Alabama
Date: 04/26/2019
Time: 07:00 PM EDT
Your letter to the bugman: I’ve began seeing these segmented, elongated bugs for the first time this year (beginning about March, when weather got warm) in the foot of nasty pool water left in our above ground pool. They swim leisurely, but can also dart very quickly.
How you want your letter signed: Amanda In Alabama
Dear Amanda in Alabama,
This is a Water Tiger, the aquatic larva of a Predaceous Diving Beetle. Water Tigers are efficient predators that eat small aquatic insects and invertebrates as well as small fish and tadpoles. Here is an image from Insects of Alberta.
Letter 19 – Water Tiger
Geographic location of the bug: Tennessee
Date: 05/12/2019
Time: 08:17 PM EDT
Your letter to the bugman: My sister had me come look at her pool over these things eating the tadpole eggs in the filter.
How you want your letter signed: Kitty
Dear Kitty,
This is a Water Tiger, the predatory larva of a Predaceous Diving Beetle. These larvae breathe through a siphon at the tip of the abdomen that breaks the surface of the water.
Letter 20 – Water Tiger
Geographic location of the bug: East Kootenay, British Columbia
Date: 06/03/2019
Time: 10:44 PM EDT
Your letter to the bugman: Found this insect floating in a freshwater lake in late May.
6 legs, approximately 2” long.
Found another smaller specimen the next day.
Suspect type of dragon fly larva but never seen one with these mouth appendages
How you want your letter signed: David
Dear David,
This is a Water Tiger, the predatory larva of a Predaceous Diving Beetle. It breathes air through a siphon at the tip of its abdomen which is why you found it floating. Here is a BugGuide image for comparison.
Letter 21 – Water Tigers
Geographic location of the bug: Massachusetts
Date: 06/05/2019
Time: 07:57 PM EDT
Your letter to the bugman: Found this in the pond in my backyard, no idea what it is.
How you want your letter signed: Alexander
Dear Alexander,
These are Water Tigers, the predatory larvae of a Predaceous Diving Beetle in the family Dytiscidae.
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