What's That Bug? does not endorse extermination

Surprised while on a tadpole rescue!
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

Water Tiger

Water Tiger

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.”

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What's That Bug? does not endorse extermination

One Response to Water Tiger

  1. Susan J. Hewitt says:

    In England there is Dytiscus marginalis, the great diving beetle. Many years ago I kept one of the (really large, up to 60 mm) larvae of that species in an aquarium for a while. “Water tiger” is not an exaggeration; they are unbelievably ferocious. The jaws of that species are long and curved. The larva would attack anything whatsoever that moved near it, including a pencil. Supposedly people have been bitten. I certainly would not have volunteered to stick my finger in the tank!
    Susan J. Hewitt

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