While “bug” often describes any small, multi-legged creature, in entomology, “true bug” refers to a specific insect group. This article clarifies their scientific definition, unique features, and how they differ from other invertebrates often mistaken for them.
The Scientific Order Hemiptera
True bugs belong exclusively to the insect order Hemiptera. This name comes from Greek words meaning “half wings,” referencing a distinctive wing structure. The Hemiptera order is large, encompassing over 80,000 described species found worldwide.
This order includes many familiar insects not commonly thought of as “bugs.” Examples include cicadas, aphids, planthoppers, leafhoppers, and stink bugs. Assassin bugs, bed bugs, and water striders also fall under this classification.
Distinctive Features
True bugs possess defining anatomical characteristics. A primary feature is their specialized piercing-sucking mouthparts, which form a structure called a rostrum or proboscis. This beak-like apparatus consists of needle-like structures, known as stylets, which are encased within a modified lower lip called a labium. These stylets are used to pierce tissues, typically of plants or other animals, allowing the bug to suck up internal fluids.
Another distinguishing characteristic relates to their wings. Many true bugs, particularly those in the suborder Heteroptera, have forewings called hemelytra. These wings are unique because their basal half is hardened and leathery, while the apical (outer) half is membranous and transparent. When at rest, these forewings typically fold flat over the abdomen, often creating an X-shape, and cover the entirely membranous hindwings. True bugs exhibit the standard insect body segmentation, consisting of a head, thorax, and abdomen.
Beyond True Bugs
Many creatures are colloquially referred to as “bugs” but do not belong to the order Hemiptera. Spiders, for instance, are not insects at all; they are arachnids. Spiders have eight legs and two main body segments—a cephalothorax and an abdomen—unlike insects, which typically have six legs and three body segments. Additionally, spiders lack antennae and possess chelicerae, which are fang-like mouthparts, rather than the piercing-sucking proboscis of true bugs.
Beetles, belonging to the order Coleoptera, are another group often misidentified as true bugs. Beetles have chewing mouthparts, unlike the sucking mouthparts of true bugs. Their forewings, called elytra, are entirely hardened and serve as protective covers for the membranous hindwings, meeting in a straight line down their back when at rest. This differs from the partially hardened hemelytra of true bugs.
Flies, classified under the order Diptera, possess only a single pair of functional wings, with their hindwings modified into small, club-shaped balancing organs called halteres. Their mouthparts vary greatly, including sponging or different forms of piercing-sucking structures, but they are distinct from the true bug’s rigid proboscis. Ants, part of the order Hymenoptera, have chewing mouthparts and, if winged, typically have two pairs of membranous wings. They are also characterized by their distinct narrow “waist” between the thorax and abdomen and elbowed antennae.