This week’s Friday 5 features a subject near and dear to my heart: giant water bugs! If you aren’t familiar with these beasts, they have some really amazing characteristics that make them a fascinating group of insects to study. I’ve already covered giant water bug parental care and feeding in other posts. Today I’m going to share 5 fun facts about giant water bugs. I hope that knowing these facts will help you fall in love with these wonderful bugs!
Lethocerus medius, the biggest giant water bug in Arizona, can reach lengths of nearly 2.5 inches!
1. The largest true bug (i.e. member of the insect order Hemiptera) in the world is a giant water bug.
Lethocerus maximus is truly a giant, reaching nearly 5 inches in length! However, if you want to add one to your collection, you’ll have to visit northern South America. The Lethocerus in the US are piddly in comparison, topping out at about 2.5 inches – half the size of the biggest species.
A male Abedus herberti cannibalizing his own offspring after he scraped them off his back.
2. Giant water bugs can be cannibalistic.
A hungry giant water bug will eat almost anything it can get its claws on, including its own young (only when very hungry or something has gone wrong with the eggs a male is caring for), the young of other individuals, and each other. Female Lethocerus are also known to rip apart the egg clutches deposited by other females when there aren’t enough males with good egg laying sites to go round. However, I haven’t observed giant water bugs eating each other in the field unless there is very little other food available and they are getting desperate. It would seem they prefer not to eat each other, but they will when they have no other choice.
Abedus herberti mating.
3. Giant water bug mating can take several hours, especially in the back brooding species.
Mating is a long, involved process in the back brooding giant water bugs. First the male does little push ups in the water. These are thought to send vibrations through the water that the females respond to. After a male and a female find one another, they mate. Then the female climbs on the back of the male and lays a few eggs, maybe 4. Then the male shakes her off and they mate again. Then she lays a few more eggs before being shaken off again. This goes on and on until most of the back of the male is covered with eggs, sometimes 150 altogether! You can see how this might take a long time. The water bugs in the photo took over 6 hours to lay all of their eggs.
Belostoma micantulum, a giant water bug from Argentina, is one of the smallest giant water bugs in the world.
4. Not all giant water bugs are giant.
Belostoma parvum, a giant water bug from northern South America, can be less than a centimeter long. It’s a not-so-giant water bug! In fact, several species of giant water bugs in the genus Belostoma are actually quite small and don’t live up to the “giant” in their name at all. The giant water bug pictured here is Belsotoma micantulum, a tiny little giant water bug that maxes out at a little over a half an inch long. Pretty cute though, especially when munching on a mealworm that is WAY too big for her! :)
The only flash flood I've ever personally witnessed, though it's hard to see how big this flood was in this photo! Clicking on the photo will take you to a cruddy, low-res video I shot of it and posted on YouTube.
5. At least one species has a nifty flood-avoidance behavior.
Imagine you’re an aquatic insect and a flash flood is headed your way. You’re going to be ground into a bloody pulp if you stick around. What do you do? If you’re the giant water bug Abedus herberti, you climb out of the stream before it floods! This species crawls out of the water and walks perpendicularly to the bank until it reaches shelter away from the stream. After the flood passes through, it crawls back into the water and carries on with its regular activities. Awesome behavior! And you can see a video of it online by visiting Dr. Dave Lytle’s website. He filmed Abedus herberti leaving the stream after artificially simulating flood conditions with a fire hose. The video is hilarious, so I encourage you to take 30 seconds out of your day to watch it.
Aren’t giant water bugs cool? I love my bugs. Considering they mostly just sit in one place hoping that food will swim by, it never ceases to amaze me just how many wild characteristics these bugs really have. Hope you enjoyed this little peek into some of the many fascinating things these bugs have going for them!
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The Dragonfly Woman 
My fun fact is that they fly. A fact that is very unsettling when one lands near you late at night. Imagine a Lethocerus in your hair.
MOST of them fly! Abedus does not, but it’s an exception among the belostomatids. Lethocerus definitely does fly though, and it makes for some exciting adventures in blacklighting!
Are you kidding~~! “imagine a lethocerus in your hair”. Im from Ny and im visiting my aunt and uncle in Ontario canada. They took me to watch some people fish near a pretty river. It was about 6:30 sun was almost set, and we were standing untop of a bridge. I had my hair down, now my hair is jet black, straight, very thick and very long. As we stood there, i heard a buzzing of wings, then a SWAT!, i friggin felt something moving in my hair. I shook my hair out thinking it was a little bug. About a minute later i still felt something moving in my hair. Well, Nowww…. i start to freak out. I start swatting at my hair and fumbling around like a mad woman. When it finally hit the ground. It was the BIGGEST bug i’ve ever seen in my life. It was about 4-5 inches long, and it had these huge pincer like things in the front. My uncle kicked it away and that was that… Pfft i tie my hair up every were we go now. Lol
I had one crawl up my waders and get tangled in the lanyard around my neck once. It was a harrowing experience having such a large, biting insect that close to my jugular! I don’t envy your experience, though I’m glad it was only scary and didn’t result in your being bitten.
We entomologists like to hang out around lights at night collecting bugs and I’ve learned through experience that it’s definitely a good idea to keep your hair pulled back if you don’t want to take a bunch of critters home with you. I myself have very curly hair so when things get in, they often can’t get back out. Definitely easier to keep my hair pulled back so they don’t get stuck in there than it is to extract all the bugs when I get home!
I just found one in the pond my sister and I swim in all summer. We also found leeches in the pond. Is there anyway to get rid of these and leeches that you know of? Are they safe to swim with in your pnd?
I don’t know of any way to get rid of either without poisoning your water, though you can scoop the water bugs out with a soup strainer easily enough. So long as you don’t grab them or step on them, though, you’re unlikely to be injured. Leeches… Those are a little harder to deal with. I actually don’t know how to get rid of them!
you say they are only in South AMerica, i had one in my house last night & my dog had another one outside where she found it. I live in Osseo, Wisconsin
Oh, there are giant water bugs in the US! Lots of them in fact. We just don’t have Lethocerus maximus, which is the biggest species. In Wisconsin, you’re seeing Lethocerus americanus if it was one of the very large ones or Belostoma flumineum if it was one of the smaller ones.
I saw one nearly 4 inches long in downtown minneapolis walking around the street. I shall live my life in fear for now on.
They don’t come out of the water very often, so you’re probably safe! And so long as you’re not picking them up or stepping on them in bare feet, they’re not going to do anything to you. Don’t think you need to live in fear of water bugs!
I just found one last night and have him in container to bring to class to show my professor! But for how long can they survive out of water?
They don’t survive very long out of water, especially if they’re anything other than a Lethocerus species. If you just add water to the container, you can keep it alive a lot longer. They really need to stay wet.
Yea i just got one right now i thought it was a horn beetle but no its a gaint water bug and i stah in minnesota