Carnivorous water beetles

I netted a monstrous (2") water beetle the other day whose claws were obviously designed for predation. There are at least two other species in the area (Cooper/Ashley drainage in SC) that are similar. I'm curious if anyone knows anything about these. I have a tank set up that would work well. It already contains a 7" grass pickerel and a water scorpion, with numerous Gambusia of various sizes plus baby convict cichlids for feeders, so there would be a continuous supply of prey.

What I need to know specifically is
- Is there a possibility of aggression toward the much larger pickerel?
- Do these actually eat fish, or would I need to provide insect larvae, snails, grass shrimp or something else?
- Do I need to be careful about identifying a target species, or do all vicious-looking beetles in the area fill a similar niche?

Dude,

If it's a dytiscus (maybe misspelled) beetle, you had better be ready for some serious carnage.
I don't know about the pickerel, but I'd bet the beetle would try for it. Everything else you mentioned
is for sure on the menu.

I had one of these beetles. Firstly, it chewed its way out of the ziploc bag I had it in, and wound up on my
"lap". Disconcerting to discover while driving.

It really loved fish and tadpoles.

Definitely a cool creature, but not a community tank member.

- Jan

PS - THEY CAN FLY.

Without a picture I will just guess that it could be an eastern toe biter. They can get quite large and are very predacious. No idea whether it could tackle the pickeral but id say anything the same size as itself would be no problem for it.

http://bugguide.net/node/view/17605 This was the first link that popped up in google.

A predacious insect and a predacious fish more than 3 times its size. You're probably not going to have much luck with that. Either the pickerel will attempt to eat the beetle, or vice versa. Not sure about the predacious beetles, but I've had a 2" dragonfly larva take down a 4" minnow. I would expect the beetle to be stronger than a dragonfly. Even though it probably wouldn't kill the pickerel itself, it could probably do a good bit of damage if it wanted to. I'm not real sure though since I'm not really a big insect person. Just fish and herps.

For keeping the beetle though, make sure you tank is covered as much as possible, because they can and will fly out of the tank. I've had that happen plenty of times.

So we're clear, everything in the tank besides the pickerel is already on the menu, and is in there for that purpose. The tank does have a cover. I currently keep it uncovered with a 10" clearance from the water to keep the pickerel from jumping out, but I could make the cover tight if I wanted to.

The tank is also partly segregated by a grate that hangs horizontally about 3" below the water surface. The pickerel is just barely still small enough to swim through the grate, but he doesn't unless I'm disturbing the tank. So far he hasn't bothered the water scorpion. I'll keep an eye on him though.

Responses so far are consistent with what I expected, but it doesn't sounds like anybody really knows. Has anyone else tried keeping them?

Jan, any idea about compatibility with the pickerel specifically?

I netted a monstrous (2") water beetle the other day whose claws were obviously designed for predation. There are at least two other species in the area (Cooper/Ashley drainage in SC) that are similar. I'm curious if anyone knows anything about these. I have a tank set up that would work well. It already contains a 7" grass pickerel and a water scorpion, with numerous Gambusia of various sizes plus baby convict cichlids for feeders, so there would be a continuous supply of prey.

What I need to know specifically is
- Is there a possibility of aggression toward the much larger pickerel?
- Do these actually eat fish, or would I need to provide insect larvae, snails, grass shrimp or something else?
- Do I need to be careful about identifying a target species, or do all vicious-looking beetles in the area fill a similar niche?

Does it look more like this http://www.royalalbe...ics/img0017.jpg the giant water bug,
or this http://www.biodivers...a194_1_327w.jpg a predaceous diving beetle.
The first one I think could pose a threat to your pickerel. They have very powerful grasping front legs and will lie in wait. Something slender and slow moving like a pickerel would be easy to grasp. I don't know how successful it would be at holding on to something that large. I have seen video where such things eat fish much larger than themselves, but don't know how many times they had to be filmed to get the shot, also could have been given a weakened fish for the video. Even so I wouldn't risk it.
I will defer to Jan about the beetle. The only time I have ever seen any aquatic beetle eat is when I toss dead mosquitos off the dock into a swarm of whirligigs.

edit to add: You might want to keep your tank covered even if you don't keep the new beetle/bug in it. I had a waterscorpion decide after a couple months of living in an uncovered tank that it wanted to go exploring. Never did find it. They can fly too.

Edited by smilingfrog, 13 November 2009 - 02:58 AM.

So we're clear, everything in the tank besides the pickerel is already on the menu, and is in there for that purpose. The tank does have a cover. I currently keep it uncovered with a 10" clearance from the water to keep the pickerel from jumping out, but I could make the cover tight if I wanted to.

The tank is also partly segregated by a grate that hangs horizontally about 3" below the water surface. The pickerel is just barely still small enough to swim through the grate, but he doesn't unless I'm disturbing the tank. So far he hasn't bothered the water scorpion. I'll keep an eye on him though.

Responses so far are consistent with what I expected, but it doesn't sounds like anybody really knows. Has anyone else tried keeping them?

Jan, any idea about compatibility with the pickerel specifically?

Well, I have not put a beetle in with a pickerel, so I guess we'll find out! Both critters are aggressive.
Do you have a pic. of the beetle you can post?
The one I had was dytiscus marginalis

Here is a picture of a Dytiscus beetle.
-Jan

If it is a giant water bug, the pickerel may be attacked. When i kept them, I would feed 2 inch rosies to a half in water bug. They grab the fish with their front legs, then jump on top of it so they can hold on easier. And the predacious diving beetles have very strong and sharp jaws. I used to feed little ones full worms, and they would just chew it up for a whole day until it was gone.
You could always just set up a small tank for it and toss in a dozen minnows.

Sorry, no pictures. I didn't keep him. If I catch another I may just buy yet another tank for it.

I've never had much luck keeping the big dytsicids. I'm not sure if it's water quality, stress, or what, but they just seem to waste away after a couple of weeks in captivity. The popcorn-kernel-sized dytiscids do fine. I haven't had an opportunity to keep Lethocerus, but its smaller cousin Belastoma seems to thrive in captivity (though I haven't had any reproduction).

One species that does well is the giant water scavenger beetle.

I agree that large predacious divers are tricker. I'm not sure of the secret but maybe cold well oxygenated water?

I've bred Abedus herberti, the ferocious water bug(but the nymphs need to be raised individually). These guys are too slow for the most part to catch fish and so can be kept with fish that you are not afraid to lose(kept them with guppies and while the occasional guppy was nabbed they were by no means skilled hunters). They much prefer to attack crickets, snails, etc.

I've never heard of anyone succeeding with Lethocercus in captivity.

The beetle referenced in the original post came from a stagnant overgrown swamp that reaches 90F in the summer, so I'd say cold water and high oxygen are not requirements for all species.