Currently viewing the category: "Water Beetles"
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.

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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.

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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

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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

Subject: i found this
Location: Florida
June 8, 2014 3:24 pm
What is it?
Signature: bigchew

Water Tiger

Water Tiger

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.

What's That Bug? does not endorse extermination

Subject: Small beetle needs identifying
Location: Midlands, UK
March 13, 2014 5:24 am
Hi,
I founf several of these small beetles in a wheat field in the UK. They have light bodies, ridged/bumpy elytra and a dark head. I can’t seem to identify it though. Do you know what species it is?
Signature: H Watkins

Unknown Beetles

Possibly Water Scavenger Beetles

Dear H Watkins,
We don’t recognize your beetles, which means we must research.  Preparing questions and images for posting takes time, and our time this morning is running short, so we are posting your images and we hope to attempt an identification as well this morning, but we may not be able to provide you with a response immediately.

Unknown Beetles

Unknown Beetles

Eric Eaton provides a very interesting identification:  Water Scavenger Beetles
Daniel:
Two of us are thinking the beetles might be water scavenger beetles (family Hydrophilidae).  Not all of them are strictly aquatic as adults, and as Doug Yanega said:  Haven’t they had a lot of rain in the UK this year?  So, if the wheat fields were flooded, or even just “soggy,” it is a fair bet to say that is what the beetles are.
Eric

Another Update from Eric Eaton:  March 17, 2014
Ok, got a more specific reply from Michael Geiser:  “Yup, I would suspect Helophorus nubilus, a species with costate elytra, well-known from wheat fields in England (even reported as a “pest species”). But I’ll wait for Robert’s reply, as he’s the expert…”
So, yes, a water scavenger beetle!
Eric

Another Update from Eric Eaton:  March 22, 2014
Daniel:
Please meet Clive Turner, a coleopterist interested in the beetles, which turn out to be a different species (not Helophorus nubilus, but a different one).  I will let Clive fill you in…..
He is interested in obtaining the specimens if the person who wrote to WTB still has them.  Thanks!
Sincerely,
Eric

 

What's That Bug? does not endorse extermination