What does it mean for a scientist to classify an insect? It means placing it within a classification system called taxonomy. In this system, each category represents a finer level of detail, moving from the most general characteristics to the most precise.
In the taxonomy of living things, the categories most commonly used are phylum, class, order, family, genus, and species. A phylum includes many classes, each class often includes several orders, and so on down to the species level.
This system, established by Swedish naturalist Carl Linnaeus (1707–1778), allows scientists to use Latin terms to name not only insects, but the living world as a whole. It is known as binomial nomenclature.
The example of the common eastern bumble bee
To determine where an insect fits within the different taxonomic categories, entomologists start by observing its anatomical features, then identify the traits shared at each level of classification. To illustrate, let’s use the common eastern bumble bee as an example.
By comparing its characteristics with those of other species that have already been classified, entomologists can identify an insect and assign it the appropriate place in the taxonomic hierarchy. The common eastern bumble bee is classified as follows:
- Phylum: Arthropoda
- Class: Insecta
- Order: Hymenoptera
- Family: Apidae
- Genus: Bombus
- Species: impatiens
To arrive at this classification, scientists determined that bumble bees, like spiders, millipedes, and crabs, have an exoskeleton and jointed legs. These shared traits place them—along with arachnids, myriapods, and crustaceans, in the phylum Arthropoda.
Among arthropods, those with a body divided into three parts and six legs belong to the class Insecta. Bumble bees, crickets, and flies are good examples. By contrast, spiders belong to the class Arachnida since their bodies are divided into two parts and they have eight legs. They are therefore not insects.
Bumble bees have two pairs of membranous wings, which link together in flight thanks to a series of tiny hooks. This feature is also found in other insects, including wasps and other bees. For this reason, these species belong to the order Hymenoptera.
Within Hymenoptera, bumble bees and other bees have hind legs adapted for collecting and carrying pollen. They are grouped in the family Apidae. Social wasps, which lack this adaptation, belong instead to the family Vespidae.
Bumble bees belong to the genus Bombus because, unlike the honey bee, they have setae (fine hairs) on their compound eyes and spines on their hind legs. Honey bees, by contrast, belong to the genus Apis.
Finally, bumble bees with a yellow first abdominal segment belong to the species impatiens.
The importance of fine-grained classification
Sometimes, the diversity within a single species calls for an even finer level of classification. For example, the white admiral is a butterfly in the genus Limenitis and the species arthemis. Within this species, there are several distinct populations that look different from one another, yet they could still interbreed if they occurred in the same area.
In cases like this, scientists can use a category that is more specific than species: the subspecies. The white admiral includes subspecies such as Limenitis arthemis arthemis (Drury, 1773) and Limenitis arthemis rubrofasciata. Even though they look different, these two subspecies belong to the same species and can therefore mate.
Finally, in the white admiral’s scientific name, the name ends with the person who first described the species and the year of the description. Here, the naturalist was Drury, who first described it in 1773. Adding the author’s name and date in parentheses indicates that the genus Limenitis has changed since the butterfly was first described.
