predacious diving beetle

Dahlia

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Sep 3, 2003
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A couple days ago I went to the LFS and they had received a giant water beetle along with the rest of their feeder goldfish. It was swimming all over the tank and a lady in the store was gawking at it in horror. She was even more shocked when I asked if I could have it... they sold it to me for the price of a feeder (.!2 cents!). I know that it is in the family Dytiscidae and it eats small fish and insects, but so far it hasn't eaten any of the feeder guppies I put in with it. They are all sizes, from baby to adult. They are all in a 20 gallon tank with no other fish (I'm not risking it eating any of my other fish)!

If anyone has any experience or knowledge of this bug at all I'd be thrilled with any stories or information. Even if it is a negative story such as an infestation killing your pond fish... I'm trying to figure out its habitat and what it will eat. Thanks!

This is what they look like (there are a lot of different species and mine is a rich greenish black with a yellow band around the edge of its body):

http://www.ento.csiro.au/Ecowatch/Primary/beetles/pages/Eretes_australis.htm
 
I used to have one as pet when I was a kid (many years ago...)

I lived in South East Asia, my black beetle was about 3 inch long. I kept it in a big water container outdoor with floating plants and fed it mostly with live earthworms and kitchen shrimps...

Very fun pet gotta be one of the most versatile creatures since it can swim/dive, crawl on land and fly in the air! I used to call it the "Water, Land and Air creature". Once in awhile, I took it inside my room and let it crawl on my desk. Sometimes, as it reach the edge of the desk, it would stop then open its wings and take off, flying around the room. Not as agile as bees or flies, but it can definitely flies. Its wings make big flapping sound as it goes...Load of fun!

One thing I gotta warn you: if taken out of the water, after awhile, it will squirts out some water from the back of its body. This water is kinda smelly since it has been "circulated" inside its body, but we kids loved it everytime it did it back then :D
 
If it actually is a giant water beetle, keep your fingers away from its mouth. If you get bit, that area of your body will go numb. It's a paralyzing venom they use to take down smaller fish.
 
>Were the kitchen shrimps you fed it alive or dead?

they were raw, dead shimps that my mom was about to cook for us (though you would more likely getting live fresh water shrimp in markets in Asia!). I had several of the beetles during my childhood but had never attempted to keep them with fish. I don't think they can swim fast enough to catch fish, but probably would ambush them, or attacking big school of small fish...

If I remember correctly, their two short front legs are pretty strong and sharp, so I didn't fool around that area...However, I think I got bit by them a few times...Can't remember if they had any venom or how strong it was. Of course, there are many subspecies that we should be careful about "testing" this!
 
Originally posted by PumaWard
If it actually is a giant water beetle, keep your fingers away from its mouth. If you get bit, that area of your body will go numb. It's a paralyzing venom they use to take down smaller fish.

I've heard that as well, and it's likely to be one as those are found in the U.S. How would you type to us your predicament if it bit your fingers?
 
getting bitten

Although I am not squeamish about bugs, I do have a healthy respect for anything that can bite. Therefore I've been making sure to handle it with a net. Even non-venomous predacious bugs can defend themselves pretty efficiently. I was moving a large praying mantis from my fennel plants to my sunflowers (I don't like it when they eat all the swallowtail butterfly caterpillars on the fennel) and she was pretty grumpy. She must not have liked being moved from her gourmet licorice-flavored caterpillars since she skewered the heck out of me with her front leg spines. I don't think I'll be grabbing this beetle to see if it can paralyze my finger or not!
 
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