Water Boatmen – Red in Tooth and Oar

By Ruth D’Alessandro, The Wildlife Gardener Nature’s cruel. Life’s unfair. The Wildlife Gardener gets it wrong sometimes. In the Wildlife Garden, a group of pond-dipping small children witnessed first hand how innocuous-looking bugs can be cold-blooded murderers… One net pulled up two 2cm beetle-like creatures with adapted ‘arms’ for rapid movement across water. Aah ” quaint little water boatmen (Notonecta glauca), like miniature rowing boats.

Notonecta glauca (c) Max xx

I picked them up and dropped them into a jar that already contained a large damselfly nymph. As I passed the jar round, one pounced on the damselfly nymph, punctured it with a spiked mouthpart and visibly sucked it dry within seconds. Cries of ‘Urgh! Gross!’ from assembled junior naturalists. For me, this triggered a traumatic childhood flashback of releasing some tiny fairground goldfish into our pond. A beetle-like creature shot up from the depths, grabbed a fish and pulled it, writhing and struggling, to the sludge at the bottom. Serves me right for introducing fish into a wildlife pond. I had always blamed a great diving beetle (Dytiscus marginalis) for abducting Goldie, but it may have been a water boatman.


The cast-off skins or exuviae of dragonfly and damselfly nymphs. These may have been shed by emerging adults, but they are also all that’s left after water boatmen have finished with their prey!

I needed to know more. My romantic Jerome K. Jerome notion of the water boatmen had been shattered. Further research revealed that water boatmen are true bugs: they have long spiked mouthparts for puncturing and sucking prey. Their bite is venomous and they have no hesitation in using that spike and venom if handled. Apparently it’s as painful as a bee sting. I’m glad I didn’t know this as I picked the water boatmen out of the net, and more relieved I hadn’t handed them round to the kids. And I vowed never to mix species in bug jars again. Now I know the nature of water boatmen, I watch the miniature dramas in the wildlife pond with new insight. A newt eft, swimming by, was buzzed by a swooping water boatman, but the little amphibian was just fast enough to evade it. Go eft, go! Thank goodness. I don’t know how much more shock and oar I can take.

21 thoughts on “Water Boatmen – Red in Tooth and Oar”

  1. Hello I was at the pool and I saw a bug swimming in the pool and I grabbed it and I now can’t feel my finger it bit me on any help

  2. We had a large number of backswimmers in our small wildlife pond. Then last year in May, over a period of a week they all left the pond and flew away. This year there are none. Has anyone noticed this kind of behaviour. Nothing had been added to the pond to make them leave.

  3. I too live in Spain and have spotted a number of water boatmen in my swimming pool. I’m suprised to learn that they have a nastie bite !!!!! and that they can fly.
    You appear to have cured the problem using a copper electrode did you buy it in spain, or have you rigged it up youself, details please if possible.

  4. I was swimm ing in my in-laws outdoor swimming pool last year which had what i beleive to be backswimmers in it, not many but a maybe 20 or so and some were quite big (upto 20mm). I used to notice them hanging onto the side about a foot below the surface with shiny backs which I think was an air bubble trapped under their wings to enable them to stay under for longer. Anyway, when I got out I noticed I was itching like mad on my back and was scratching it agaist a brick wall it irritated so much. The lump was pretty big, like a bee sting and lasted for about a week before going away. It wasnt a mosquito. I’m pretty sure it was a Backswimmer. I looked them up on the internet that night and discovered they bite. I now kill any that I see and am careful not to handle them.

    In response to Alan; I notice there are none this year yet, the only difference in the pool is that the water is being run through a copper electrode. The water is crystal clear and you need only a tiny amount of chlorine. I have not seen any bugs alive in it yet. Last year there was all sorts in there alive.
    Hope this helps.


  5. We’ve got them in our pool, sometimes lots (my son and I scooped out over 100 this spring); yesterday I grabbed one with my hand to throw it out of the pool and the little sucker bit me! I was really surprised (hence my internet search today!). It hurt a little bit, not as much as a bee sting, but now, 24 hours later, my finger is swollen and painful! And yes, they do fly, I was surprised to find out when cleaning out the skimmer basket. So my son stomped on those 100+ “oar bugs” as I dumped them from the skimmer net into the dirt… please don’t call PETA – they’re just bugs!

    1. Back in the early 1950s, very little me was given a 6 pence (2.5 pence now ) plastic net on a bamboo cane. Then encouraged to use it to find the creatures in a small pond of the type used for cattle to drink from which many fields had back then. Avoiding the several frogs and numerous tadpoles, the first time I dipped it into the pond, I pulled out a magnificent Great Crested Newt. WOW!

      Enjoying this, further dips into the pond revealed other species newts. No idea what they were. Then I had a shock, one of two shocks I was to experience that day. My net pulled out the most fearsome creature I have ever seen. So nasty and ugly looking. I put it back quickly because quite frankly the thing scared me. I have since discovered what it was. The fully grown predatory larva of a magnificent Dragonfly …Golden Ringed Dragonfly .. Cordulegaster boltonii. The second shock, several cheeky looking little creatures with “oars” swimming about quickly on or near the surface. I picked one out of the water. BIG mistake, my goodness that “sting” hurt.

      Those learning experiences sewed the seeds of a lifetime’s interest in all the creatures, the good, the bad and the ugly we share this planet with. I recommend any youngster to try it to.

  6. Wise, Sue. I keep my fingers well away! Yes – the boatmen probably had some of your efts, but so have the dragonfly larvae, diving beetles, any fish, perhaps even a sneaky grass snake! I look at fully-grown frogs and newts and marvel at how lucky they are.

  7. I just found myself wondering why we had far fewer efts than last year, when we set up our wildlife pond and were lucky enough to get loads. I have watched our four resident water boatmen (who are now huge and appear to be territorial!) and now I think I know… I also pick things out of the ‘gunge’ to throw back in, but let the boatmen swim out of the net first!

  8. Hi I wonder if anybody can help. I have a swimming pool in Spain & all the levels of the pool are correct. The problem I have is water boatman. i have quite a few in the pool & have tried in vain to get rid of them. I have shocked the pool quite heavily twice but to no avail. Can anyone help please? Thanks in anticipation. Alan

    The Ranger responds: these things can fly, Alan. The pH of your pool won’t make any difference if they’re flying in from somewhere else. Any pool water would be extremely hostile for any invertebrates; they wouldn’t live long anyway, so you’ll probably get lots of dead ones in your filter too. Perhaps you’re downwind of some wetlands?

  9. Your fish will be making a bigger dent in the amphibian population by eating eggs and newly-hatched tadpoles than the water boatmen will be!

  10. We have masses of backswimmers in our pond and having clearly established they dish out a painful bite my children are keen to remove and destroy any we’re able to catch. My dilemma is whether they’re serving a useful function in eating algae and contributing to the overall balance or whether they will be dining on our much loved tadpoles, frogs, newts and fish if left alone. Advice gratefully received !

    The Ranger responds: no, they’re not eating algae, but yes, they are definitely contributing towards the natural balance. Notonectids are voracious predators and they certainly will have a go at tadpoles or pretty much anything (although when they grow up into frogs the frogs get their revenge!). But they won’t wipe them out, and having them in your pond shows that it’s a good, healthy natural pond. Fishing them out will be pretty ineffective as unless it’s a tiny pond you’re unlikely to make much impact on their numbers. In nature, things do eat things, except in human-tamed environments like gardens or zoos. You’ll need to decide which way you intend to manage your pond, but if you choose to try to keep the predators away from their prey you could have a big task ahead of you!

  11. I think that is a backswimmer and not a water boatman. I need confirmation though. They are extremely similar except that backswimmers swim on their back and backswimmers are the one with the notable bite. I’ve always read research that suggests that boatmen – who swim right-side up – don’t bite.

    The Ranger responds: go for the scientific name, Josh, it usually solves such mysteries. Notonecta glauca is known as both a water boatman and a backswimmer in English (see here). You’re also right in that the lesser boatman – Corixa – doesn’t bite and swims on its front.

  12. I have just taken some green slimy stuff off the top of the Wildlife Pond, and I picked carefully through the gunge to release any critters. The thought of chancing upon a water boatmen unnerves me more than giant diving beetles and dragonfly larvae!

  13. I was down at th stables with my pony the other day and one of the kids down there wanted some *bugs* to put in his water. We went to the trough in the field and I picked some up and put them in his bucket. From one or two of the boatman I felt a nasty tingle from. This only lasted for about 5 minutes. I thought I was just being silly, but now I know that they realy do sting! x

  14. I was bitten when I went fishing in my Grandpa’s pond. None of the adults believed me! I didn’t know that they stung, so it was a bit of a shock when it hurt.
    Fred, age 8.

    The Ranger responds: poor Fred! I hope they believe you now!

  15. Hi Tricia! Ouch! That had to hurt! If it’s any consolation there are now baby water boatmen in the Wildlife Pond that are being eyed hungrily by rapidly growing dragonfly larvae. I haven’t yet witnessed a retaliatory strike. Check out my beetles blog for a furry little cutie that doesn’t bite!
    The Wildlife Gardener

  16. Hi Wildflife Gardener,
    I was cleaning out our pool fliter today and felt this … bee like sting on my finger.. I dropped the fliter and looked down to see a boatman… OUCH it really hurts.. I agree with Laura I was cursing.. just like a bee sting.. the area swelled and has a red dot just like a bee bite.. I’d say it lasted around 10 min or more…


  17. Ranger Laura – my turn to be fascinated – is it really like a bee sting and how long does the pain last for? I feel reluctant to test it myself…. The Wildlife Gardener

  18. You’re welcome, Maureen! If it stops one person picking a water boatman up and getting a nasty bite it will all be worth it!

  19. I’m ashamed to admit that I’ve never heard of water boatmen. I was fascinated by this very interesting post. Thanks for the lesson!

Leave a reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.