Currently viewing the category: "Water Beetles"
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Killer bug!
Hi all,
I caught this little guy while trolling ditches for inverts for my naturalized tank at work. He was about 2.5″ long and particularily vicious. He killed virtually ever other invert in the tank, stole food from the 9 shiners and 1 “wild-caught” koi and the small frog and generally made a demon of himself. I think it’s a hellgrammite? Or some kind of stone nymph. Anyhow, the tank overheated one weekend during a power failure and i lost killer bug and my frog. 🙁 Keep up the good work! Cheers,
Vancouver, BC

Hi Alicia,
This is a Water Tiger, the larva of a Predaceous Diving Beetle. There is an interesting description on a website known as Findarticles. We are sorry to hear about you stewing your local fauna tank. It sounds like a refreshing change for the usual jobsite aquarium. We once kept a Los Angeles River aquarium going for five years. Though the winged insects flew away, the three mosquito fish produced many generations until they finally succumbed to a rogue raccoon. We kept the aquarium outside on the patio.

Update: (11/04/2007) edible: water tigers
Hi Daniel and Lisa Anne,
I hope you both had a good trip to D.C. Both larval and adult predatory/scavenging water beetles are eaten in China and Southeastern Asia. A batch of adult Water Beetles were collected for me in Louisiana this past summer; I hope to receive them soon. They were gathered with light traps that some insect-hunters used; swarms of various insects came. I’m wondering if any of your readers know of people who collect insects this way, and if anyone has tried putting lights over the shallows of a pond to attract larvae and other water insects. If so I’d love to learn about their experiences. Best,
Dave Gracer

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Whats this bug called?
We were berry picking and my daughter found this insect in a mud puddle.Could you tell me the name of this insect,thanks.

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.

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What is this!
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!

Hi Dan,
This is a Water Tiger, the larva of the Predaceous Diving Beetle. Looks like it caught a minnow.

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Any ideas please ?
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.

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.”

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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.”

What's That Bug? does not endorse extermination