Giant Water Bug
Updated: Dec 5, 2019
I shared a photo of a recent insect find on my Instagram account and, to my great amusement, a friend commented: “I found one of those last summer. It was absolutely horrifying.”
I was more horrified that I thought it was a cockroach. However, upon closer inspection, what I really had stumbled upon (almost literally, as the creature was resting center-sidewalk) was Minnesota’s largest insect, the Giant Water Bug!
Maxing out at 2 inches long and 1 inch wide, the giant water bug is 2 square inches of buggy awe. They have a handful of daunting nicknames like “toe-biters” and “alligator ticks”, and those are well-earned: These largest members of the scientific order Hemiptera are predatory insects which feed on tiny fish, amphibians, snails, crustaceans, and even baby turtles and water snakes! If provoked, giant water bugs will bite people, but it’s less a bite with pincers or teeth and more a severe poke with it’s oversized, mosquito-like rostrum, a sort of syringe to both inject its prey with a pre-digestive toxin and to suck down the juices as it eats. (Note: While the bite itself is painful to humans, the giant water bug’s toxin is harmless.)
The water bug should not be confused with water beetles. Why? Though they are all aquatic insects, beetles are not bugs and bugs are not beetles. The word “bug” isn’t just slang for creepy crawlies that give us heebie-jeebies, but “bug” is also an actual category of insect, more accurately referred to as the “true bugs”. True bugs number around 80,000 different species, of which our own giant water bug (Lethocerus Americanus) is one, as well as our last Local Wild discussion subject, the very vocal cicada. Giant water bugs and cicadas make up a large portion of the insects commonly eaten by humans.
True bugs are distinguished from other insects in a variety of ways, but two in particular stand out. First, unlike beetles, bugs are hemimetabolous, which means they do not have a larval stage (they don’t start off as grubs) and do not pupate (they don’t metamorphize inside a cocoon). Instead, giant water bug nymphs (juveniles) hatch from the egg as miniatures of their adult form and shed out of their exoskeletons about 5 times before reaching their full size.[i] The second notable difference is that bugs eat a liquid diet using their straw-like rostrum while beetles possess sharp mandibles that grasp, cut, and crush solid food or prey.[ii]
Another distinction between the giant water bug and a water beetle (of which Minnesota has 6[iii]) is that of the beetles two sets of wings, the first is generally considered the beetle’s “shell” since it is hard and serves to protect the more delicate flying wings laying beneath. Water bugs also have two sets of wings, but they’re just sort of… soft. All over.
And that fact, combined with the giant water bug’s ferocious nicknames and impressive size, actually does give me some heebie-jeebies.
[i] “Giant water bug”, Alimentarium Foundation. URL: https://www.alimentarium.org/en/knowledge/giant-water-bug. Accessed: 18Aug2019.
[ii] NLN, Laura. “What’s the difference between a bug and a beetle?”, NaturallyNorthIdaho.com, 26Sept2014. URL: http://www.naturallynorthidaho.com/2014/09/whats-difference-between-bug-and-beetle.htm. Accessed: 17Aug2019.
[iii] “Images by Category: Aquatic Invertebrates”, MN Department of Natural Resources, 2019. URL: www.dnr.state.mn.us/minnaqua/leadersguide/lg_online/images_category/invertebrates.html#beetles.