Okay, so. Insect anatomy.
And I should state right out of the gate that insects are arthropods, but ‘arthropod’ isn’t synonymous with ‘insect.’ We’ve got woodlice and centipedes and spiders to point that one out. Insects are a specific type of arthropod, and that type is characterized by one set of antennae, three pairs of legs, compound eyes, and three body segments. They typically have two pairs of wings when they have wings.
So, let’s just go down the bug, shall we? (Also, it seems reasonable to point out at this juncture that there are such things as real bugs, or “true bugs,” as Science likes to say, presumably because it sounds less sarcastic that way. They’re in Suborder Heteroptera, and what makes a true bug a true bug is partially beyond the scope of this post and partially a Sartrean nightmare of an existential feedback loop.)
The head is where they keep their dorky little mouths and most of their sensory organs. Two antennae, compound eyes (the honeycombed-looking things), simple eyes (most people don’t notice these), and more mouth arrangements than you can shake a stick at.
A praying mantis admirably displaying its weird insect face. It’s got chompy mouthparts*, two compound eyes taking up like three quarters of its little bug face, two not-weird antennae, and that little triangle of simple eyes. The simple eye, which is technically called an ocellus, can’t tell it a whole lot and mostly keeps the bug in question up to speed on changes in light levels and so forth.
The thorax (chest) is where insects keep their legs and wings, and where they generally keep most of their muscles and some of their breathing apparatus. The wings and leg arrangement are pretty damn important when it comes to identifying which bug is currently crawling in your hair. Most insects with wings have two pairs of wings (forewing and hindwing). Sometimes these are more or less identical, and sometimes you have like the beetle configuration where the forewing isn’t a wing anymore, it’s a hardened wing cover, and fuck you for expecting two sets of things that looked like wings.
Above: Bee wings hook together so that they function and look like one larger wing during flight.
Below: Beetles are what’s worst in life.
In addition to how they work together and similarities or lack thereof between the pair, vein pattern can also tell you a lot about which bug is which. See the little black stained-glass looking patterns?
They’re veins. They pump hemolymph (bug blood) around the wing and provide structural support for the membranes. So you can have wings that look like that (dragonfly), and wings that look like this:
(blue morpho butterfly)
If you want to go completely nuts with the wings, there are charts for that:
Above: One of many.
The abdomen is where insects keep their digestive, respiratory, and reproductive tracts and, commonly, their defense mechanisms. It’s not always immediately clear to a casual observer where the thorax ends and the abdomen begins, but most insects have a reasonably clear demarcation.
Above: Head, thorax, and visibly segmented abdomen of a damselfly.
Below: Fuck everything of a diving beetle.
So let’s sort of put this into practice for a minute, because if you’re currently going cross-eyed and wondering why the fuck you’re reading this, it might help.
We’re going to do this by playing “Are you a love bug?”.
Above: The humble love bug (Plecia nearctica), a type of march fly that subsists on nectar during its adult phase. Note the orange dorsal hump on its thorax, the large compound eyes and the relation to the rest of the headcase, short and smooth antennae, kind of snouty mouthparts (for nectar consumption), the soft but hairless abdomen, and the fairly standard wing veins.
So. Are you a love bug?
No, you are something else. You have long antennae, a hard abdomen, a completely orange thorax, chompy mouthparts, and those evil little wasp eyes. This is because you’re an argid sawfly (Arge quidia).
Are you a love bug?
No, you’re something else too. You have long and fuzzy antennae, a soft fluffy abdomen with a very fluffy butt, an orange collar that only covers part of your thorax, and coiled-up butterfly mouthparts. This is because you’re a grapeleaf skeletonizer moth (Harrisina americana).
So, why do we care if the wasp and the agricultural pest aren’t love bugs? Dude, did you see the wasp? It’s a wasp. Of course we care about the difference between a wasp and a love bug.
*Mouthparts are available in a wide variety of configurations, from “chompy” to “stabby” to “oh god make it stop.”
[Top picture from here.]