Water Boatman

2008 May 17

Water boatmen, like this one, are all over the place. They can fly, so they end up in bodies of water ranging from full-blown lakes, to puddles and birdbaths. This particular one was at the mouth of Cole’s Creek, just down the road from our house.


They look kind of beetle-like, but they are actually in the family Corixidae, which are included in the Heteroptera, or “true bugs”. There are a bunch of species of water boatmen, but it isn’t realistic to try to distinguish them down below the family level, because they all look the same: head with big eyes, streamlined body, and the two hind legs elongated into “oars” for swimming. They aren’t all that fast overall, but when they paddle with those oars, their motions are so jerky, and they are so able to dart off in random directions, that they are somewhat hard to catch[1]


I’m not quite sure what their mouthparts look like. If they are like other true bugs, they would have a “beak” for piercing and sucking, but water boatmen are reported to eat algae and small plankton, which sounds more like the sort of thing that you need to either chew up or lick up. Their front legs are modified to have little scoops on the ends, which look like they are suited for sweeping up tiny floating things in the water:


This is one of the features that distinguishes them from another type of small aquatic bug: the “backswimmers”. Backswimmers are about the same size and shape, and have the same sort of elongated legs with oars on the ends, but (a) backswimmers are predatory, so their front legs are designed for grabbing things and don’t have the little scoops; (b) backswimmers swim upside down, while water boatmen swim right side up; and (c) backswimmers can bite you if they are handled roughly, while water boatmen are harmless. You probably don’t want to use that last item for identification if you can help it, though.

Unlike the other aquatic insects that I’ve found so far, water boatmen actually breathe air. They trap an air bubble under their abdomen and can breathe with this air bubble for some time. If you look at the first picture, you can see the fringe of little hairs sticking out from the back of his abdomen that help to hold the air bubble underneath.

There is a big bonus from breathing air instead of water: oxygen is not very soluble in water, and so even well-aerated water doesn’t supply all that much oxygen. Grabbing an air bubble from the surface not only privides oxygen at much higher concentrations, it also allows the water boatman to live in water that is kind of stagnant and oxygen-poor.

Some species of water boatmen can also make noises, kind of like a cricket, that they can use to call mates through the water. They sound like this.

They aren’t really committed to the whole aquatic lifestyle, this one was perfectly happy to climb up out of the water and onto the side of the dish:


And, somewhat unusually, they can actually fly directly from the surface of the water. In fact, they can evidently shoot up from underwater, pop through the surface, and fly away[2]! This is not something a lot of insects can do, usually they have to haul themselves out of the water before they can spread their wings and fly off.  One of the things that lets them do this is that their sufaces are highly water-repellent.  The one in the picture above just crawled out of the water a few seconds before the picture was taken, and I can’t see even a single water droplet or moist patch anywhere on it.  That’s how completely it shed water.

[1] We caught this one by quickly sinking a large container right behind it. The sudden inrush of water sucked it right into the container. Voila! I think if we’d tried putting a jar over it, or netting it, it would have gotten away, or at least taken a lot longer to catch.

[2] Like Supercar!

24 Responses
  1. June 2, 2008

    I loved watching these scoot about on the water when I was a kid!

  2. June 3, 2008

    Yep, me too. Funny thing is, I was never able to catch one when I was a kid, but catching this one was a piece of cake. I guess it’s just a matter of coming up with the right technique.

  3. June 3, 2008

    What kind of bait did you use on your hook? I probably would have gone with some kind of nematode.


  4. Casey permalink
    September 13, 2008

    Question for you — if you have enough of these in a garden pond, do you think it would have any significant impact on algae since you said they like to eat it…?

  5. September 13, 2008

    That’s a good question, I don’t know. I’ve never seen them in particularly high concentrations, though – they probably fly off to look for greener pastures as soon as the population starts getting too large. In that case, they wouldn’t ever get numerous enough to help much. Unlike, say, snails.

  6. Rob permalink
    October 26, 2008

    We were just draining our pool and found about 10 of these. I think this is the same bug. Pretty wild!

  7. robyn somers permalink
    November 28, 2008

    Dear sir/madam
    Question to you: Do Boatman feed on algae

  8. November 29, 2008

    Yes, they do.

  9. richard permalink
    June 21, 2009

    We was opening our pool and found one of these. they r wild! we had no idea wat it was cause it stayed under water for so long. we thought we had a fish in our pool!

  10. melissa permalink
    June 6, 2010

    i was helping my mom clean the pool and a white one was on the cover so i picked it up and it bit me, it actually hurt like a wasp sting. i was suprised

  11. June 7, 2010

    That was probably a backswimmer, then. They are carnivorous, look a lot like water boatment, and definitely are biters.

  12. Jim permalink
    July 16, 2010

    How do you keep them out of the pool.

  13. July 17, 2010

    Given that they fly in, I don’t know if there is a way to keep them out of a pool, other than covering it. If it is a swimming pool, though, they won’t survive the pool chlorine.

  14. Graha013 permalink
    June 9, 2011

    Looking up information on these guys – I was loading my truck before heading to work one day and glanced at the tonneau cover that was covered with rain drops from last night and saw a mark and a dragging trail where something had landed and tried to crawl away. I followed it down the cover and found a brown bug that I recognized from childhood as the ‘water boatman’. I took a little shot glass of rain water from a potted aloe plant I have and popped him in and now have him in a small, rectangular ‘aquarium’ (for lack of better word) that is 6″ long, 5″ tall, and about 2″ wide. Originally I was going to use it for bamboo stalks, but now it houses ‘Dobby’ and a stick of sun colia (sp) which can live planted or submersed in water. As the only critter in this tank, it’s fun watching him swim along and he seems to be perfectly happy staying – he craws out on the plant and at the slightest touch drops back into the water, or takes refuge in the low hanging leaves/rocks. With the plant in there, I’m not worried about him starving, but I do drop a fish pellet in every once in awhile to add some detritus and biological substance to the water.

    It’s been over a month now and he’s still kicking! Most bugs you kind of expect to die with shorter lifespans – any idea how long they live? I’m almost tempted to find and put 1-2 more in there and see if they mate and breed – can’t find any information on them about that though (bug sex, ew!).

    All of the sites I find are about scientific information or getting rid of them – nobody except me and my weird office keeps them as a pet! lol

  15. June 9, 2011

    I’m not sure how long they live either, it sounds like you might be in a position to tell us after a bit. It sounds like it overwintered as an adult. Insects that do that usually mate and lay eggs sometime in the spring or early summer, and then die, although how long that takes can vary quite a bit.

    If you could get a couple more, have them mate, and establish a population, that would be quite amusing!

  16. Graha013 permalink
    June 9, 2011

    Is there a contact form for you? I’d like to send you a couple of pics, see if you can’t definitely ID it (boatman or not, I haven’t seen a pic matching his markings)

  17. June 9, 2011

    Actually, your best bet to ID it would be to go to the Water Boatman pages at BugGuide:


    If you don’t find a match yourself, you can easily go to the upper-right corner and register yourself at BugGuide (it’s free) and upload your pictures to that page. A number of people who are far more expert than I am will then probably be able to tell you what you have.

  18. Graha013 permalink
    June 9, 2011

    Thanks for that. Ironically, the body shape is much more rounded than most of those specimens, and he is a deeper brown with some gold/lighter markings only at the tail end that makes a sort of half circle design. Small head, small eyes…he doesn’t really match at all. I’ll upload there and try to get some better pictures of him and see if I can identify…and cross fingers it’s not the Hidden Vampiric Waterboatmen or something like that 😛

  19. Graha013 permalink
    June 9, 2011

    Acilius mediatus. Not a water boatman at all.. predacious diving beetle.

  20. July 6, 2011

    i just caught to water bugs while swimming i think they are very cool how do they mate though because my dad said that they dont

  21. grogon permalink
    August 26, 2011

    do they eat water snails?

  22. Jessica Powell permalink
    September 30, 2011

    There ugly !!!!!

  23. beth permalink
    October 26, 2011

    they look cute

  24. Jamie permalink
    November 1, 2011

    As a kid (41 years ago), I found one of these swimming in our pool. I took it out of the water and it flew away. It’s something that I have thought about many times over the years. It didn’t seem possible that it survived the chlorine, but especially that a swimming insect could fly. Thanks for setting me straight.

Comments are closed.