Butterfly Systematics

What is Systematics?

The science of systematics gives us the tools to communicate clearly about the natural world, and imposes order by describing the relationships between living organisms. Scientists name and put organisms into groups based on their evolutionary history (how closely related they are). These groups start very general and large, for example plants or animals, and become increasingly specific. Each species has a scientific name that anyone in the world can recognize.

The field of systematics is an active one, full of debates about the true evolutionary relationship between species and groups of species as well as the details of how we should represent and name those relationships. Systematists (people who study systematics) construct genealogies that represent their best understanding of the evolutionary relationships between species. To do this, they use specific traits called taxonomic characters. These characters are attributes that differ between groups. Historically, taxonomic characters were most often morphological traits such as the form, shape, or structure of an organism’s different parts. For example, taxonomic characters for a group of birds might include beak shape and size and wing shape. In Lepidoptera, important morphological traits include the shape of the genitalia and patterns of wing venation.

In the past few decades, systematists have acquired powerful new tools to study the relationships between species. For example, electron microscopes, which can magnify objects more than 100,000 times their normal size, allow scientists to look at tiny details of small structures such as eggs, scales, or pollen grains (see the scanning electron microscope pictures in Butterfly Sensory Systems earlier in this section). Using biochemistry and molecular biology techniques, systematists can also study the differences between organisms’ DNA and proteins. Molecular similarities and differences between organisms can then be used to judge how closely related the organisms are.

How are Organisms Classified?

People have classified and named organisms for millennia. Some scientists today, for example, study Native American names for plants as they work to classify new species. In the eighteenth century, a Swedish physician and botanist named Carolus Linneaus developed the naming system we use today. Using Latin and Greek words, Linneaus gave thousands of species two-part (binomial) names based on characters such as their appearance or origin. After Linneaus, binomial names replaced common names, such as garden pea or monarch butterfly, in scientific discussions and writing. Since the common name for a species often varies in different places, or may be used for more than one species, this system allows biologists to communicate more clearly.

The first part of a scientific name is called the genus name. A genus is a taxonomic classification of organisms that are closely related. The second part of a scientific name is called the specific epithet and differentiates between members of a genus. Together, the genus and specific epithet provide a unique name for every species, or kind of organism. Some scientific names of familiar species are:

Homo sapiens—human

Megaptera novaeangliae—humpback whale

Panthera leo—lion

Ursus horribilis—grizzly bear

Octopus vulgaris—octopus

Canis familiaris—domesticated dog

Danaus plexippus—monarch butterfly

Notice that the scientific names of these species are printed in italics. If you are handwriting a scientific name, you underline it. Scientific names are almost always descriptive. Using Latin or Greek, scientists name an organism for its appearance, its locality, its behavior, or to honor its discoverer. For example, Homo means human in Latin and sapiens means wise or knowing, so Homo sapiens refers to wise humans. Octopus means eight feet and vulgaris means common.

Let us look more closely at Canis familiaris to understand the other groups into which organisms are classified. The species name for dog originates in Latin: Canis means dog and familiaris means common, or familiar. Canis lupus is the scientific name for wolves. Because wolves and domesticated dogs are very closely related, they share the same genus, Canis. But dogs are also put into groups with other animals. This list includes all these groups, starting with a group that contains all animals, and ending with the group that contains only domestic dogs.

Kingdom: Animalia

Phylum: Chordata

Class: Mammalia

Order: Carnivora

Family: Canidae

Genus: Canis

Species: familiaris

Start from the bottom of this list to see how scientists have grouped dogs with other animals. Remember that the scientific name of an organism is just its genus and specific epithet put together.

The specific epithet for domesticated dogs is familiarius. This group contains all domesticated dogs, even though different breeds may look quite unlike each other. They can all interbreed, which is an important criterion used by scientists to determine what constitutes a species. Domesticated dogs are grouped with their close relatives into a single genus, Canis.

Genera (the plural of genus) are grouped into broader categories called families. The “dog” family, called Canidae, also includes coyotes, foxes, and jackals. Common traits of these related genera include an elongated jaw with 42 or 44 teeth, five toes on the front feet, and four toes on the back feet.

Families with similar characteristics are put into the same order. The dog family is in the order Carnivora (Latin, to eat flesh), which also includes bears, cats, and other meat-eating animals. The presence of canine teeth (fangs) distinguishes this order.

Similar orders are grouped into classes. Carnivores are in the same class as us, Mammalia. Mammals are distinguished from other classes of animals by hair and by the birth of live young who feed from specialized mammary glands as infants.

Similar classes are put into the same phylum. Mammals are in the phylum Chordata, along with related classes such as amphibians, reptiles, and fish. All members of this phylum have a nerve cord running down their back. Most members, including humans, are called vertebrates. In vertebrates, the nerve cord is enclosed in a backbone made up of small bone units called vertebrae.

Finally, all phyla (plural of phylum) are grouped into the next largest category, called a kingdom. The animal kingdom includes vertebrates, insects, segmented worms, shellfish, and all other multicellular organisms that cannot make their food from the energy of the sun. Scientists recognize five kingdoms of living organisms: animals, plants, fungi, bacteria, and protists (one-celled organisms that have a different cell structure than bacteria).

The table on the next two pages compares the classification of monarch butterflies and humans, starting with their kingdom, and describes the characteristics of each group to which they belong. (Note: the numbers of living species are accurate as of January 2021. Also remember that these numbers can fluctuate with scientific research and debate. Sources may state different numbers.)

Comparing Monarch and Human Classification

Butterflies vs. Moths

Lepidoptera are divided into dozens of families. Generally, we think of these families in two groups: butterflies and moths. However, if we drew a “family tree” that accurately showed the evolutionary relationships between butterflies and other Lepidoptera, it would show that some moths are closer relatives of butterflies than of other moths. Butterflies are best described as a group of moths that has “escaped” being nocturnal and is most active during the day.

Butterflies and moths usually can be distinguished by the following traits. There are, however, exceptions; for ex- ample, a few moths are active during the day and some butterflies have “fuzzy” bodies.

This content was originally published in the Monarchs & More curriculum (4th Edition).