Wheels on the bug go ’round and ’round…

For your Friday afternoon, I thought I would write briefly about one of the more awesome bugs that you will find in the US. Meet the wheel bug!

The wheel bug (Arilus cristatus) belongs to the order Hemiptera, which means that it is, in fact, a true bug. Seems like an odd way to phrase it, right? A ‘true bug’, as opposed to what? Spiders? Ticks? Turns out, this is one of those taxonomy things that entomologists like to get all geeky about. Works like this:

All bugs are insects, but not all insects are bugs.

If we want to get technical about things, for an insect to truly be a ‘bug’, it has to belong to the order Hemiptera. In general, to be a member of this elite classification of insects, you have to have a particular type of sucking mouthpart called a proboscis. Now is when someone needs to call me out and say “Wait! Does that mean that mosquitoes are true bugs as well, since they have a proboscis designed to suck blood?” No, smart ass. Mosquitoes are flies, belonging to the order Diptera. There are a number of morphological features that can be used to identify what order an insect belongs to, as well as other traits such as life cycle and development. True bugs, in addition to the beak, or proboscis, typically have four wings that that overlap to fold flat over the abdomen. A good indicator is to look at the base of the wings for a triangle shape where the wings do not overlap. This is called the scutellum (see the image below, and ignore the pin head…it is a mounted specimen).

Mosquitoes, like most flies, have only two wings (see image below).

True bugs also go through a life cycle known as incomplete metamorphosis (hemimetabolism, sometimes called ‘simple metamorphosis), which means that they start as an egg, hatch into a nymph (basically an immature version of the adult insect), and then continue growing and developing until they finally reach the adult stage (kinda like human babies look relatively human, but still have a ways to go).

This is in contrast to flies, beetles, butterflies and other insects that undergo complete metamorphosis (holometabolism), in which the egg hatches into larva (that does not resemble the adult…think caterpillars and butterflies), develops and grows until it forms a pupa (imagine hiding in a sleeping bag for a few weeks as your body reassembles itself into something better-looking), then emerges as a full-fledged adult.

Nice. I managed to include a photo of ladybug sex. Anyhow, there are a lot of features that can be used to identify and classify insects. In fact, classifications change all of the time these days as researchers learn more about the genetic relationships between different insects. It is not unusual to learn that two different species of insect, which might appear similar (and therefore closely-related) to the naked eye, actually diverged from one another millions of years ago.

Now back to the wheel bug. Ever since I was a wee lad, out collecting insects in my back yard, I have thought that wheel bugs were pretty awesome-looking. They are one of the largest true bugs in the North America, and feed upon other insects using their large proboscis. It is kinda like they have a straw for a mouth, and they stick it into other insects and suck the juice out. Insect vampires, maybe? Except they are not undead. Poor analogy. Anyhow, they are Wheel Bugpretty slow-moving, and relatively harmless to people, though if you mishandle it, you will learn pretty quickly that they can deliver a pretty nasty poke. I just found one the other day, crawling on the window of one of the classrooms. Then today, a friend spotted one on her car and requested identification, so I thought I would share it with all of you. If you have never seen one before, they could appear a little intimidating, but there is no need to fear! They are quite helpful too, since they often feed on insect pests. Just relocate them to a convenient shrub, and take a moment to enjoy watching a pretty awesome-looking bug. Also, feel free to correct others (in a somewhat superior tone) the next time that they refer to a non-Hemipteran as a ‘bug’. Just, uh…make sure identified it correctly first, ok?




Category(s): Entomology

4 Responses to Wheels on the bug go ’round and ’round…

    Gary Robinette says:

    I also admire your blogging ability and have enjoyed the knowledge. But, to continue using photos of lady bug sex I feel will require an “R” rating.

    Marjorie Willner says:

    Engaging stuff.

    I never thought that there might be true bugs – do they come earlier on the phylogentic tree than the other insect you named?

      sequencingscott says:

      Good question. To the best of my knowledge, they do not diverge particularly early on the phylogenetic tree. Here is a good example. There are certainly examples of more primitive insects. Remember that the name for the overall group is ‘insect’. The word ‘bug’, as applied to insects, has a bit of history to it. I remember learning in an undergraduate entomology class that the word originally came from an old Welsh word that sounds like ‘boog’, relating to evil spirits, and is the origin of the word ‘boogeyman’. It has been suggested that people once attributed bites and sickness from bedbugs (lice) to spirits, and that is where the word bug came from. I tried to verify this just now, but the best that I could find at the moment was this one link (though you can gain some information from looking at origin information in various dictionaries).