All bugs are insects, but not all insects are bugs

I have always called insects bugs.  I know I’m using the wrong word most of the time since the word bug refers to a specific group of insects.  If I’m not talking about that one group, using the word bug instead of insect is technically incorrect.  If you’re around many entomologists , using the word bug to describe an insect that is not actually a bug is like scraping your fingernails down a chalkboard – highly annoying.  I don’t know. I’ve always found this attitude somewhat pretentious and counterproductive.  As an entomologist myself, I like to promote insect awareness and get people interested in what I do.   It’s hard to get people interested in what you do when they feel belittled because you corrected them for using a word they didn’t even know was wrong.  I use the word bug for all insects, even though I know I am wrong to use it most of the time (and yes, I have been corrected by other entomologists myself!), for several reasons:

1) It’s easier to say bug than insect.

2) I find people relate better to stories about bugs than stories about insects, especially when they know I’m an entomologist or if they are kids.

3) I happen to work with insects that are, in fact, bugs.  When you constantly use the word bug to describe your work, even in scientific papers, you get in the habit of using the word bug all the time.

Really, though, how many people who aren’t entomologists know the difference between an insect that is a bug and an insect that is not?  It’s a subtle distinction and most people don’t have any reason to learn the difference.  For those of you who don’t know what makes a bug a bug, allow me to enlighten you!

The insects are divided into about 25 smaller groups called orders.  All insects belonging to an order share certain traits, which is why they are grouped together in the first place.  A bug is an insect that belongs to the order Hemiptera.  Members of the order Hemiptera are also called true bugs, hence the word bug.  If you’re being technical, only insects that are true bugs should be called bugs and everything else should just be called an insect.  But how do you tell a true bug apart from other insects?  All true bugs share two main traits: hemielytra and piercing-sucking mouthparts.

The word hemielytra refers to the specialized top pair of wings (forewings) of the true bugs.  Most insects have 4 wings and true bugs are no exception.  Some insects, like beetles, have hardened forewings that protect the more fragile hindwings underneath.  These are called elytra.  Take a look at this palo verde beetle’s elytra:

palo verde beetle

A beetle. The arrow points to this beetle's elytra.

The true bugs have hemielytra, not elytra.  The forewings of bugs are only hard for part of their length instead of the entire length.  The upper part is thick and leathery and the lower part is membranous, about the same texture as the hind wings underneath.  Look at the forewings of this giant water bug and look for the differences in these wings compared to those of the beetle pictured above:


Giant water bug. The arrow points to the hemielytra.

See the dark section of the wing toward the back end of the bug (to the right of the tip of the arrow)?  That’s the membranous part.  The rest of the wing is the thickened, leathery part and a completely different texture.  True bugs often have a sort of V-shape to their wings.  See the V just to the left of the tip of the arrow?  For the most part, if you see this V-shape in the wings of an insect, you’re looking at a true bug.  (Note: I’ll talk about that big, long piece sticking off the back of the giant water bug in a future post.)

The other trait that all true bugs have is piercing-sucking mouthparts.  Different insects have different types of mouthparts, but most people are familiar with insect chewing mouthparts.  This is what caterpillars, beetles, and grasshoppers have.  They use these mouthparts to grind their food up before swallowing it as the first step in digestion.  Look at the chewing mouthparts of the palo verde beetle:

palo verde beetle head

Palo verde beetle head. The arrow points to the chewing mouthparts.

Palo verde beetles have really big mouthparts that are easy to see.  These things can actually bite quite hard, even drawing blood if they get you in the right place!

In contrast, true bugs have piercing-sucking mouthparts.  Instead of putting food into their mouths and grinding it up the way beetles do (and humans too!), they inject digestive chemicals into whatever they want to eat using their mouthparts (hence the piercing part of “piercing-sucking mouthparts”).  These chemicals break the food down into a soupy mess which the bugs then suck into their mouths through their mouthparts (that’s the sucking part of “piercing-sucking mouthparts”).  It’s a lot like eating your food with a straw!  Check out the mouthparts on the giant water bug:

true bug bealk

Giant water bug mouthparts. The arrow points to the piercing-sucking mouthparts.

The piercing-sucking mouthparts of true bugs are often called beaks because they are long and pointy like a bird’s beak.  Can you see the similarity?  Unlike birds, bugs can fold their beaks down under their heads, which is how the beak of the giant water bug above is positioned.

An interesting aside: Bugs can have a really nasty bite.  That little straw-like mouthpart might not look that impressive, but remember how bugs eat: they inject digestive chemicals into their food.  If you handle one improperly or startle one, those same digestive chemicals can end up in your fingers!  They can’t do any lasting damage, but it can hurt a lot as it digests some of your muscle.  It’s usually a good idea to handle true bugs with care.

So now you know!  A bug is an insect that has hemielytra and piercing-sucking mouthparts.  The next time you want to get technical and use the word bug for an actual bug, think about whether the insect in question has that V-shape to its wings and a long beak folded down under its head.  If so, it’s a bug and you can use the word bug without fear or hesitation!  If not, you can still call it a bug.  The choice is yours after all.  Just expect any entomologists nearby who happen to overhear you to correct you.


Text and images copyright © 2009


25 thoughts on “All bugs are insects, but not all insects are bugs

  1. I am a scientist at the University of Maine. We are developing an image-based key (to family level) for dragonfly larvae in the Northeast. You blog is great – I wondered if I might have permission to put a link to it in our “Links” page on our site (which is not live yet – but it’s almost done!)


    • Sure! I would love to have my page linked from yours! I’m a fan of anything that promotes insect education to the public, and an even bigger fan of widely available visual keys to insects. I did a visual key to many of the Tucson dragonflies a few years back and it was a lot of fun (though also a TON of work and it unfortunately remains incomplete). I hope you are enjoying it!

  2. I just found your blog. Good stuff. There are surprisingly few blogs like this. I like what you are doing to inform and educate people interested in aquatic insects.

    My undergraduate students and I have established web sites tailored to specific streams where high school biomonitoring teams work and it may be of interest to you:

    Sarah, I look forward to seeing your dragonfly site also!
    Declan McCabe

    • Thanks for the comments and the link to your rivers website! It sounds like a wonderful project, the sort of thing I would really love to do once I have finished my Ph.D. and have a real job. :) I love teaching people about aquatic insects because I feel like there are so few people that know anything about them. When I did my last outreach event, my number one question was: “Wait, dragonfly nymphs are aquatic?” The fact that people don’t know that even the most showy and popular aquatic insects have an aquatic stage suggests that there is a huge gap between the people that study aquatic insects and the public. Aquatic insects just aren’t taught! I hope to fix that. Glad to see there is someone out there who is drawing lots of people into the subject!

  3. Hi, just a note about Palo Verde Beetles: You show the “chewing” part of the PVB. You might find it interesting to know that the adult beetle does not have a digestive system or excretive system and does not eat as an adult (although they will accept water).

    • Interesting! Do you have a source for this information I can check out? I’d love to read up more on it!

      Even if they can’t eat, they still have impressive mandibles. They might be using them for something else now (I’d assume combat!), but they’re a good example of what chewing mouthparts look like in an insect.

  4. Hello there! I’m writing a blog post on assassin bugs and while explaining the difference between an insect and a bug, I have confused myself. I came across your post and thought maybe you could answer a question. have a nice bug collection and when I visit classrooms I tell students that insects/bugs are either “suckers” or “chewers.” So if bugs are suckers that have an elytra, and many insects are chewers, what are mosquitoes and flies? Are they insects that “suck?” (LOL, that sounds funny). I hope you can satisfy my curiosity!

    • Flies are mostly spongers, with the exception of the mosquitoes (which do suck), the horse flies and deer flies (they slice), and a few others. If it helps, think of the sucking flies like the mosquitoes as suckers that lost a pair of wings. (Hmm… Now I have an image of a helpless fly playing poker against a card shark and losing the wings off his back in a hand gone horribly, horribly wrong!) That way you’ll have suckers with hemielytra and suckers that lost a pair of wings to distinguish between the bugs and the flies.

      • Okay, so I’m incorrect in the suckers vs chewers. I will add “spongers” to the list! I find myself trying to put things into neat little categories even tho I KNOW that’s not how nature works. Must…fight…the…urge! That night after I wrote you, I started thinking about how aphids are technically bugs but don’t have elytra…or am I going to drive you crazy now? LOL. Thanks for the fun analogy on the flies and mosquitoes. ;-)

        • Ah, yes! Aphids ARE bugs but don’t have the hemielytra. That’s because the true bugs used to be in the order Hemiptera and the aphids, cicadas, scale insects, planthoppers, etc used to be in the order Homoptera. Hemiptera had sucking mouthparts that arose from the front of the head and hemielytra while the Homopptera had sucking mouthparts that arose from the back of the head and entirely membranous wings (if they had wings at all). They’ve since been combined into one group based on the shape of the sucking mouthparts. The true bugs (as they used to be defined) currently fall into the suborder Heteroptera and the order Hemiptera now includes all the insects with piercing-sucking mouthparts.

  5. Thanks for an interesting post!

    Thought I’m not an entomologist, I am one of those people who is irked by the misuse of the word “bug”.

    I agree that belittling folks generally isn’t a good approach to addressing ignorance, particularly when the subject of conversation is one where there’s a deep, pervasive social prejudice (like the subject of insects). That said, what irritates me is the lack of basic scientific literacy that’s demonstrated. We have perfectly good categories — insects and arthropods — to cover the general concept of “bugs”. It’s INTERESTING to understand the differences between these categories, and explaining them can be a part of being a creepy-crawly ambassador. But more importantly, the line of thinking the lets most folks see “bugs” as encompassing all of the “lower” animals, from insects and other arthropods to even snails and worms, is exactly what maintains the social prejudice.

    I think I’m very much saying the same thing you’re saying in substance, but wanted to speak in defense of communicating — politely, and with genuine good will — the uninformed misuse of the word “bug”. Still, given your professional background and clear interest in reaching a broader audience, I can appreciate your choosing to adopt the term for the reasons you mentioned.

    • You know, I usually try to gauge how receptive a person might be to my explaining the differences between the two and go from there. I work with giant water bugs, true bugs, and people call them beetles all the time. Then they turn right around and call beetles and other insects bugs even though they are not true bugs. It does drive me a little nuts sometimes! So, if I think I can correct someone who is receptive to gaining a bit of extra knowledge, even if it just becomes a fun fact they can share with others, I usually do. With other people… Well, sometimes it’s not worth the argument.

  6. People referring to yellowjackets as ‘bees’ did at one point drive me batty…and then there’s ladybird/ladybug. I have mellowed and I’m happy to hear anyone actually talking about insects without derision….

  7. yes its true that ” All bugs are insects, but not all insects are bugs” lots of people think that all bugs are insects and insets are all bugs.. thank you for sharing this to us its very informative specially for those that doesn’t know about this.. There’s this one also that is confusing the butterfly and moths. lots of people sometimes think that they are the same, And this book can help you differentiate them..You should have one..This will help you a lot..

  8. Dfw, have you ever taken a whack from one of your Belostmatidae? I fell into a swamp once as a teenager and had several latched on to me within a few seconds. I couldn’t understand why I was in so much pain, I couldn’t even think…

    The reason I ask is that while it is well known that these guys pack a punch, it seems people tend to associate the assassins with “worst bite” (wheel bugs often come up…) despite being lower on the Schmidt pain index. I’m trying to find experiences by someone who has felt both (which is incredibly uncommon). I may have to go search the woods for a wheel bug this spring and take a whack for the sake of science…

    • No, I have never been bitten by one of these, so I don’t have any way to commiserate with you unfortunately. I was told early on that their bite is really awful, so I’ve worked very hard to avoid situations where I might be bitten. However, I will say that the Schmidt pain index is specifically focused on Hymenoptera. Justin’s a bee guy and let’s himself get stung, but he doesn’t do much with Hemiptera. Perhaps you can start a Cortese Pain Index for the bugs? Though honestly, I suspect that most bug bites are FAR worse than most of what Justin got himself into, so it’s not going to be a fun experience at all.

  9. Pingback: A Wheel Bug is a real bug | walter sanford's photoblog

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