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Ever had a Water nymph cause trouble in any of your tanks? Now, I dont mean the sort of nymphs found in mythology, I am referring to the larval stage of some winged insects like mayflies and such. They are mean looking buggers and grow quite large.

I've seen them in my molly fry tank from which I've lost 2 of the original 16 that were born, apparently they come with the plants, in this case Elodeas. One of the fry I found was somewhat mauled over, maybe by older and stronger fry, maybe for other reasons. Nontheless since I've removed the nymph from the tank, a 1.5-2 inch long, clear-light green creature with long legs and mean looking mandibles, I have not experienced any more deaths at all in that tank (knock's on head ...I mean wood).

Recently, I setted up a tank with live plants and have stocked it so far with 1 farlowella, 2 loricarias, 3 cardinal tetras, 5 marble hatchetfish and 5 red phantom tetras. In a matter of two nights I lost two fish, one each night, both the smallest of their shoal(3/4 of an inch long). First night I lost a cardinal tetra that showed no apparent sickness or scarring on its body. Second night I lost a Red Phantom and I noticed it was struggling upside down on the bottom of the tank, I took it out to put it in the hospital and noticed it had its caudal fins eaten up and its tail peduncule somewhat mauled.

I searched the tank and found a pupa or coccoon with a larvae inside of about an inch long attached to a Giant Val leaf, the pupa was put together by joining 3 Elodea leaflets together with a mucus like membrane, I assume excreted by the insect.

Is it possible for insects in their nymphal stage to be the culprits of my demise or could the mauling been done by another fish?

Thanks in advance,

James

This is very much a reality.
the larval, or nymph stages of insects from the order (odonata)dragonflies, (plecoptera)stoneflies and (ephimeroptera) Mayflies are aquatic and predatory. They eat things such as fish, small frogs, and other insects at this stage in there life. The dragon fly larvae will grow up to 2.5 inches long so you can see what kind of damage that that would inflict.

-Vincent

Budzilla,

Good to hear from you again and thanks for your prompt reply, thought I was delussional when all the facts pointed to the nymph as the culprit. Poor fishies though. Hope I got rid of the bugger and he will not take any more victims!

Again many thanks for backing up my findings.

Best regards from CR

J.

No problem,
its important that people now that, I had dragonfly larvae killing 2 inch goldfish in my outdoor pond last year. I only realize what was happening when I found the exoskeleton of one.

-Vincent

They actually make excellent pets on their own. A couple of caddisflies in sand gravel makes for one mighty entertaining aquarium.

Dragonfly nymphs , caddis fly larvae,diving beetle larvae, etc, all commonly refferred to as nymphs. They are the most predatory stages of these insects, large dragonfly nymphs are quite capable of killing fish as large as adult sticklebacks, or in aquarium terms most fish under 2 inches long, and some of the smaller amphibians like newts and salamanders too. Tadpoles of most species are a favourite on their menu.

Amazing creatures though they may be, they are voracious eating machines with jaw structures that can dispatch most small fish, you dont want them in an aquarium, well, unless you want them in your aquarium (lol) but dont expect the fish to do well! They can eat huge quantities in proportion to their size, as they compusively put on as much weight as possible so they can metamorphose to the adult stage as quickly as possible. Even so , many can stay in this voracious larval form for several years. A large dragonfly larvae could eat several neon tetras a day, thusly being able to empty a tank of even a large shoal in a few months.

I know it seems a shame to kill such amazing critters, personally im very fond of most aquatic insect predators, I find them fascinating, but unless you know they came from a local water system you must not release them into the wild, they can obviously do a lot of damage if released into the wrong ecosystem.

Squishing time methinks! Unless of course you want to set something up so that you can raise them yourself to see what they turn into, a small aquarium with a bit of weed or bogwood protruding from the surface,so it can leave the water and change to the final instar when it feels the urge, and feeds of live midge larvae, bloddworm etc, and pieces of chopped earthworm for the larger specimens. A good and appropriate use for those little nano tanks. No need to splash out on lots of equipment though, theyre usually not too fussy about water quality. Adult diving beetles make good pets, although what you do with an adult dragonfly of 3 -8 inches long other than release it, if its a local boy, or build a butterfly house if it isnt , I dont know! I suppose you could always gas it with co2 and have a nice little preserved specimen in a glass case! lol.

If a non-indigenous nymph found its way into my tanks im pretty sure id never see it anyway.Either the polypterus, the larger cichlids or the catfish would probably pummel the hell out of it anyway. MMMMM crunchiness!Nymphs, living hell to some, gourmet treats to others .

This is a hawker dragonfly larvae, you can imagine the small scale killing power of this larva

http://www.countrysideinfo.co.uk/Pond/FOLDER01/Souther_Hawker_Dragonfly_larva.jpg
Hope this helps.

one of my first two-foot tanks (over 30 years ago)was devoted to aquatic insects, including water-boatsmen and lots of nymphs, all caught out of our dams and river. it was sensational! i kept it on the verandah and the bugs could just fly off when they finished their metamorphosis. some of them, i can't remember which ones,would decorate their silk sheaths with whatever you put in with them. i sometimes used to delicately pull them out, put them in a jar of water, and add different coloured sand and stuff so they would make coloured homes. then back into the main tank. hours of fun! but yes, they'll stalk and eat all sorts of stuff - heaven help if they were our size. move over, predator!!

Those will probably be the caddis fly larvae, they are famed for weaving silk casings and camouflaging them with tiny stones.A perfect cover for an ambush predator.I always wondered how insects get sticky silk threads to bond and mature into a hard shell underwater. Its amazing stuff. Dragonfly larvae have terrifying mouthparts, a huge retractible lower jaw that fires at prey rather like HRG's "alien". If they were three feet long, WE would be on the menu! Ive also seen studies that some beetle larvae eat compulsively 10 items a day, and feel compelled to make at least that many kills, even if its more food than they need,or can possibly digest effectively, which is very unusual in nature. They are quite scary little critters in their own way.

I told my old science teacher in junior school that his greater diving beetle would eat his 3 inch crested newts.He didnt believe me, but when it ate them I milked out a "told you so" for about a year!The beetles very conspicuously decided to eat one a newt in front of the class. I just dived in and saved the last newt , despite being told not to, ran out of school and released it into the local park. I got a clip round the ear, and sent home with a nasty note to my parents for that one Thankfully my dad, who is a self righteous git, just the same as me, came to school and gave the teacher a talking to that left him looking more than a little dishevelled, if not completely pale Teachers really can be a bit thick, especially when hearing the truth from a 7 year old kid Theres another endangered species that got a bit rarer thanks to the sages in our schools .lol.

Actually, Mayfly larvae (Order Ephemeroptera) are largely herbivorous. Likewise, most Plecoptera (Stoneflies) have herbivorous, algae grazing aquatic nymphs. I had a Stonefly nymph appear in my aquarium a few years back - I only found it when I discovered the dead nymph tangled up in Java Moss near the bogwood "boot" in my aquarium. If that nymph had been predatory, it would have dined quite happily on my assorted small Characins and Panda Corys, and I'd have been losing them systematically over time.

Most Ephemeroptera are algal grazers or detritivores, with a few modified to become plankton sifters, and a very small minority that are predators on other aquatic insects. Trichopteras (Caddis Flies) are variable, but many again are detritivores, with only a small minority of predatory species that feed upon other aquatic insect larvae. Most of the UK species are definitely detritivores, and are ecologically important because they are part of the Particulate Organic Matter chain (POM for short). One of my invertebrate zoology colleagues at Liverpool Museum, Dr Ian Wallace, studies these professionally for a living, and gave an excellent presentation on them at a past meeting of the Entomology Society.

The predatory nymphs are Odonata (Damselflies and Dragonflies, some of which are large and serious predators of small fishes), and certain Coleoptera (Beetles with aquatic larval stages - the Dystiscus beetles are big enough to be a threat to a fish the size of a Mikrogeophagus ramirezi Cichlid, but you're not going to miss either the larva or the adult because it's a juggernaut!).

It would be well worth acquiring a handbook of aquatic insects to differentiate between the various larval forms. Distinguishing between the various Orders can be confusing if you're not accustomed to dealing with insects, not least because some Orders still provide the professional entomologist with some headaches!

As an example of the fun and games that can ensue, go to this thread, and scroll down to my photo of the larva of Acilius sulcatus that turned up in a Daphnia shipment some time ago (back in 1998). This creature is manifestly predatory and was helping itself to my Daphnia at a rate of knots ... fortunately it was large enough to be removed from the Saphnia before I fed the fishes, otherwise who knows what havoc THIS creature could have wrought?


Panda Catfish fan and keeper/breeder since Christmas 2002

and there was me hoping to read about mermaids!
Good grief you guys know a lot of stuff......
GFG



_______________________________________
Never be bullied into silence. Never allow yourself to be made a victim. Accept no one's definition of your life; define yourself.
Harvey S. Firestone

They most certainly do. Thank you all for your knowledgable responses they are full of of usefull information.

Made me feel like I was back in biology class and regressed me a few years back...ok more than a few years back!

Did some research and from my observations alone I do believe that I had a Damselfly nymph in my molly fry tank. Lets see if I remember classification correctly from my bio class. This is fun!

Order: Odonata
Suborder: Zygoptera
Family: Coenagrionidae

Going any further down the ladder of taxonomy would be speculating too much since I don't have the specimen to compare it to any classifying key.

Nontheless, the culprit looked pretty much like the one on this link.... link, but instead of being brownish it was more of a light green colored.

It is amazing how many things can affect aquaria and how delicate and intresting the components of it can be. For instance, some nymphs may predate on fish on that stage of their metamorphosis, while in other stages or even adulthood they may be predated by fish.

That is the cycle of life, intrincate and intresting.

Thank you all for your replies, hope to keep hearing from you in the near future.

James

If it is any help at all the difference in larvae in odonat a are this. Damsel Fly larvae have 3 distinct gills on their abdomen while with dragonflies they have 3 spines and internal gills.

-Vincent

Right on the money as always Mr. Vincent. The distinguishing feature I remember from the specimen caught was the distinct feather-looking gills at the end of the abdomen, thus indicating me that it was more likely to be a damselfly.

Thanks

J.