Crash Course in Taxonomy, or, What Those Odd Latin Terms for Bugs Mean

Perhaps you’ve noticed that our Bug Week writings often contain Latin terms for bugs.

For example, if we mention the common bed bug we’ll probably reference its scientific name, Cimex lectularius. Or when we talk about grasshoppers we might note that they’re part of the insect order known as Orthoptera.

Maybe you’ve wondered what all this terminology meant.

We’ll try to explain…

The first thing to know is that there’s an entire scientific discipline devoted to identifying and classifying organisms. It’s called taxonomy. When someone discovers a previously unknown species of insect, taxonomists are the people who determine what insects are closely related to the newly discovered species, and taxonomists are the people who come up with a formal, scientific name for the new critter.

Let’s talk about formal, scientific names for a moment.

One of the main reasons for using scientific names is that common names aren’t standardized. For example, what one person calls a “giant water bug” someone else may call an “electric light bug,” someone else calls an “alligator tick” and yet another person calls a “toe biter,” and perhaps none of these four people realizes that they’re all talking about the same type of insect. But if you say “a member of the Belostomatidae family,” there’s no room for misunderstanding – assuming that you know what Belostomatidae means in the first place.

Generally, organisms are given a scientific name that contains two words. This name represents the smallest taxonomic division that’s possible for an organism. For example, the luna moth goes by the scientific name Actias luna and so if you gathered up 1,000 male and 1,000 female specimens of Actias luna, all the specimens in each gender group would be virtually identical, even if you carefully examined them under a microscope. You might notice some minor variations in their color and size, but all these specimens would be so similar that any randomly chosen male and female could mate and produce viable offspring. In fact, that’s one of the standards used in determining whether two groups of organisms are members of the same species – can a male from one group and a female from the other group reproduce?

Scientific names use Latin words (or what passes for Latin – we’ll get to that in a moment.) For example, the invasive mosquito species commonly known as the Asian tiger mosquito has the scientific name Aedes albopictus. Each word has separate meaning – “Aedes” comes from an ancient Greek word that means “unpleasant” and “albopictus” means “white-painted.” So, Aedes albopictus means “unpleasant, white-painted mosquito,” more or less. In a scientific name, the first word is always capitalized. Also, the scientific name is generally written in italics, to emphasize that this is a Latin term.

Now, the first word in the scientific name is the name of the organism’s genus. The genus is the next-largest taxonomic classification after the species. There may be many organisms in a genus, or just one. Regardless of the exact number, all the organisms in a single genus are closely related. In the mosquito genus Aedes there are dozens and dozens of species – they all have scientific names that start with “Aedes” and then have a unique second word that denotes the species, to distinguish them from other members of the Aedes genus. So besides Aedes albopictus we also have its close relative, Aedes aegypti, the yellow fever mosquito – same genus name, different species name.

When someone finds a previously undiscovered organism, a taxonomist studies it and writes a very detailed description of its anatomy. This description will eventually “go on record” as the formal set of characteristics that this species possesses. The taxonomist who handles this task usually gets to assign the species name to the organism – the second word in the scientific name. It used to be that a taxonomist would usually select a species name that was a Latin term for a noteworthy characteristic of the organism – as we mentioned earlier, “albopictus” means “white-painted,” which refers to the white markings on the legs and body of the Aedes albopictus mosquito.

However, in recent decades it’s become common for taxonomists to assign species names that are meant to honor people. To “Latinize” the names, there’s often a letter “i” added to the end of the honoree’s name, rather than a real attempt at translating the name into a Latin equivalent – this shortcut is probably taken to ensure that it’s obvious who is being honored. For example, in the world of tropical fish, there are dozens of species with scientific names that end in “axelrodi,” to honor ichthyologist Herbert R. Axelrod, a major figure in the tropical fish hobby. That might seem reasonable, but lately things have taken a non-scientific turn and it’s now fairly common for celebrities to have organisms named in their honor. In the entomological world alone, there’s a spider named for Harrison Ford, Calponia harrisonfordi; a wasp named for Lady Gaga, Aleiodes gaga; and a beetle named for Sigmund Freud, Cyclocephala freudi. If you’re interested, there’s a long list of examples on this Wikipedia page — http://en.wikipedia.org/wiki/List_of_organisms_named_after_famous_people.

Confidentially, we here on the BugWeek webteam find this trend silly and a bit disconcerting, because it eliminates one clue – species names based on notable traits – that can help scientists and amateur bug enthusiasts identify puzzling specimens. Here’s what we mean – it’s sometimes difficult to determine an arthropod’s genus and species by casual inspection, especially if there are several species that look alike. When the species name references the critter’s appearance or habitat or behavior, the name can help us determine what we’re examining. We can only hope that Calponia harrisonfordi seldom gives interviews (probably true) and that Aleiodes gaga is always wearing a fancy hat (probably not true.)

Okay, one more thing to discuss (and thank you for reading this far, by the way) – the taxonomic hierarchy. This will help explain why we throw around terms like “Coleoptera.”

In taxonomy, each organism is typically classified at eight levels, starting with a very large group and gradually working down to the very small group we’ve discussed already, the species. This hierarchy is similar to the way that a Florida resident’s home address can be classified by eight levels – planet, continent, country, state, county, city, street and exact house number.

From largest to smallest, the taxonomic classifications for living things go like this:

Domain

Kingdom

Phylum

Class

Order

Family

Genus

Species

One easy way to remember the correct progression for these terms is to memorize the phrase “do kangaroos prefer cake or frosting, generally speaking?” The first letter of each word in the “kangaroo” phrase corresponds to the first letter in one of the classification terms.

Let’s look at the terms used for one bug, the European honey bee, Apis mellifera

Domain – Eukaryota (organisms with cells that have nuclear membranes)

Kingdom – Animalia (animals)

Phylum – Arthropoda (arthropods, ie. animals with exoskeletons and jointed legs)

Class – Insecta (arthropods with six legs, compound eyes and one pair of antennae)

Order – Hymenoptera (often flying insects with some specific anatomical traits)

Family – Apidae (a family containing most bees)

Genus – Apis (honey bees that sting)

Species – Apis mellifera (the European honey bee)

You’ll notice that only the genus and species names are italicized.

There are a few other classification terms that occasionally show up, such as subphylum, superfamily, subfamily, tribe and subspecies. We’re not going to worry about those right now.

Aside from the genus and species names, the two taxonomic terms you’re most likely to encounter in BugWeek material are phylum and order. Let’s take a quick look at those before we wrap up –

Phylum – Among animals, there are about 35 phyla (“phyla” is the plural form of “phylum.”) Virtually all organisms that are commonly called “bugs” are part of the phylum Arthropoda. This phylum includes all invertebrates that have exoskeletons, jointed bodies and jointed legs. Members of this phylum are called arthropods. Insects are arthropods. So are spiders, scorpions, centipedes, crabs, lobsters and shrimp. In case you’re wondering, there are some organisms people might call “bugs” that are not arthropods. They include snails and slugs (part of the phylum Mollusca), worms (part of the phylum Annelida) and nematodes (part of the phylum Nematoda.)

(Thus far, we’ve limited BugWeek coverage to members of the phylum Arthropoda, though we’re thinking about expanding our coverage next year.)

Order – Among arthropods, there are about 33 orders. An order is a classification that is narrow enough that the average person might recognize that its members have general similarities. For example, among insects, the Odonata order contains dragonflies and damselflies; the Dermaptera order contains earwigs; and the Coleoptera order contains beetles. The one arthropod order that the average person might recognize by name is Lepidoptera (the insect order containing butterflies and moths). In case you’re interested, the insect order Coleoptera, the beetles, contains more species than any other animal order, and includes about one-fourth of all the formally described animal species on Earth – about 400,000 species. What’s more, it’s believed that there are actually at least 1 million beetle species alive today – most of them undescribed – and possibly as many as 100 million.

Wow. Looks like the taxonomists are not going to run out of work anytime soon.

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— Tom Nordlie