Is it a Bug?
Hello fellow insect enthusiasts!
Have you ever wondered whether or not the thing everyone refers to as a “bug” is actually a bug at all? Or even an insect for that matter? In this post, I will be talking about the differences between most of the creatures collectively referred to as bugs and why most of them are not actually bugs in a scientific context. This is going to be a very technical article, so put your thinking cap on and let’s dive on in!
Definition of a Bug
Let’s start at the bottom and work our way up. A quick Google search (the starting point for any quest for knowledge) for the “definition of a bug” reveals that a bug is “a small insect.” Well that’s all fine and dandy, but I think we knew that already. A bug wasn't going to be something colossal and lumbering, it was going to be something small and skittery. To further discern what a bug is, let's take Google's definition and expand it a little more: let's define what an insect is.
Definition of an Insect
two compound eyes, two antennae, two sets of wings, and a hard exoskeleton.
An insect is an organism in the phylum Arthropoda. Arthropods have a hard exoskeleton that covers most of their body (which means they have no internal bones, like humans do). Out of the arthropods, insects are then further classified in the subphylum Hexapoda, which simply means any arthropod with six legs. True insects are classified under Hexapoda with the Collembola (springtails), Diplura (two-pronged bristletails), and Protura (coneheads). Insects are in the class Insecta, which is where taxonomy finally gets specific enough to differentiate insects from other arthropods. Generally speaking, an insect could be anything with a hard exoskeleton, six legs, three body segments, two compound eyes (usually), two antennae, and two sets of wings (usually). Insecta is such a large class that there are plenty of exceptions to this definition of insect, but it covers the vast majority of the creatures that are found therein.
Excluding Non-Bug Organisms
So far, we’ve defined a bug as something small, with a hard exoskeleton, six legs, three body segments, two compound eyes, two antennae, and two sets of wings. This definition now excludes worms, spiders, crustaceans, centipedes, millipedes, scorpions, and mites. Worms are in the phylum Annelida, which immediately separates them from the arthropods, and from being included in the definition of a bug. Spiders are arthropods, but only have two body segments (the cephalothorax and the abdomen), eight legs, and eight eyes! Way too many to be an insect, and way too many to be a bug. Crustaceans generally have more than six legs, which keeps them out of the Hexapoda and ultimately out of the definition of a bug. Centipedes and millipedes also have far more than six legs and more than three body segments, but do have an exoskeleton, which places them under the Arthropoda, but not in the Hexapoda. Scorpions and mites are actually more closely related to spiders than they are to insects. They are both arthropods, but have too many legs and an inappropriate number of body segments, keeping them out of the Hexapoda and out of the definition of a bug.
The True Bugs
Can any insect be a bug then? Scientifically speaking, no. A quick look at the second definition provided by Google’s dictionary sheds some light on this: “an insect of a large order distinguished by having mouthparts that are modified for piercing and sucking.” From this we can conclude that a bug has piercing, sucking mouthparts. This correlates to the order Hemiptera, which includes all insects with a piercing, sucking mouthpart. Some examples might be whiteflies, or aphids, or cicadas. These insects like to suck the juices out of plants and are correctly referred to as bugs.
Pentatomidae (stink bugs or shield bugs) are true bugs in a taxonomic sense.
But even within the order of bugs, there are actually a subset of insects referred to as “true bugs.” These special insects include creatures like the assassin bug (Reduviidae), stink bug (Pentatomidae), leaf-footed bug (Coreidae), and even the bedbugs (Cimicidae)! Bugs such as aphids, whiteflies, and cicadas, while still technically a bug, do not fall under the taxonomic identification of a true bug. Confusing, to be sure, but that's taxonomy for you.
A quick summary of what we’ve discussed so far: the term bug applies to arthropods with six legs, three body segments, two compound eyes, two antennae, and two sets of wings. Taxonomically correct usage of the word applies only to those insects in the order Hemiptera, and technically only to those insects in the suborder Heteroptera, which are the true bugs.
But here’s the kicker: for all intents and purposes, the everyday use of the term “bug” is correct in just about every situation discussed in this article. Thanks to the way English works, bug correctly applies to every creepy-crawly thing you come across. Thanks English.
Thank you for reading this post! Comment below on some insects or bugs you've seen!
~Let’s Go Find a Bug