Currently viewing the category: "Water Beetles"
What's That Bug? does not endorse extermination

Subject: Green pool bug or shrimp?
Location: Tampa, Florida
April 8, 2016 3:49 pm
Hello,
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.

What's That Bug? does not endorse extermination

Subject: Swimming pool bug
Location: Canberra Australia
October 22, 2015 9:58 pm
Hi Bugman.
I left my above ground swimming pool uncovered for approx. 6 months over winter. I didnt clean it nor did I add any chlorine. Now that its getting warmer I thought time to clean it out and start getting it healthy again. When doing so I caught 11 of these swimming bugs and I just needed to know more.
They swim to the water surface and sit there facing downwards (with the backsides toward the top).
When I stir the water they dive to the bottom (approx. 600mm) where I can’t see due to the leaves and other garbage – then do not come up for at least 5 minutes.
They appear to have 6 legs, two tails (split) and two clippers or claws on their face. They are very good at staying absolutely still, but when they swim they have a fish like turning movement. It should be noted that when I pulled them out of the water, they had no troubles walking around, moving almost like a scorpion.
I have attached a video and some pics.
This is in Canberra, Australia. Currently October (middle of spring) and heading towards summer.
Appreciate if you had any ideas on what these are?
Signature: thank you

Water Tigers

Water Tigers

These are Water Tigers, the aquatic larvae of Predaceous Diving Beetles in the family Dytiscidae.  There is a nice simple explanation of the life cycle of the Predaceous Diving Beetles on the Australian Museum website where it states:  “Larvae have a siphon (like a snorkel) coming out the end of their body. They stick this siphon out of the water to get oxygen to breathe.”  According to the Missouri Department of Conservation site:  “Larvae, called ‘water tigers,’ are elongated, flattened and can be 2 inches long. They commonly come to the surface to draw air into spiracles (like snorkels) located at the hind end of the body. There are 3 pairs of legs, and the jaws are strong pincers that are used to grasp prey.”  The Natural History of Orange County, California site has some nice images of Water Tigers.  As you can tell by our links, Predaceous Diving Beetles are found in many places on the globe.

What's That Bug? does not endorse extermination

Subject: What is it
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

Predaceous Diving Beetle Larva

Predaceous Diving Beetle Larva

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.

What's That Bug? does not endorse extermination

Subject: Odd beetle/roach
Location: Johnston, Iowa
July 19, 2015 8:52 pm
Hi there,
My dad and I found this bug in a window well behind our house while cleaning out a lot of leaves. The bug was pretty big- as large as any roach that I’ve ever seen in Iowa.
The window well is on the north side of the house and behind a large hosta. A couple weeks ago the downspout detached and with 5″ of rain the well flooded and water flowed into the basement through the window. So it is fairly moist down there. We also found two frogs/toads in the well.
Anyway, this bug was found on 7/19/2015 in Johnston, Iowa. Our neighborhood is relatively flat and we live within half mile to a creek that eventually feeds into the Des Moines River.
Signature: Coen Wiberg

Giant Water Scavenger Beetle

Giant Water Scavenger Beetle

Dear Coen,
What a nice discovery.  This is a Giant Water Scavenger Beetle in the genus
Hydrophilus which you can verify by comparing your image to this image posted to BugGuide.  According to BugGuide, they can be found in:  “stagnant/slow waters; prefer deeper water (weedy ponds, deep drainage ditches)” and “Some adults overwinter on land, under leaf litter. Others may remain under ice of ponds and stay active all winter. Lifespan may exceed one year. Adults may be found at lights in summer as they disperse.”  If there was a light in the window well, it might have attracted this Giant Water Scavenger Beetle, and if there was also water present at the time, it may have found the location to its liking.

What's That Bug? does not endorse extermination

Subject: Star Trek brain eater
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

Water Tiger and Mosquito Tumbler

Giant Water Scavenger Beetle Larva and Mosquito Tumbler

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.

Water Tiger and Mosquito Tumbler (front and center)

Water Tiger and Mosquito Tumbler (front and center)

Water Tiger

Giant Water Scavenger Beetle Larva

What's That Bug? does not endorse extermination

Subject: unidentifiable front pincer bug
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

Water Tiger

Water Tiger

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.

What's That Bug? does not endorse extermination