The body of a goldbug was circular and flat. As their name implied, their outer carapace was golden in color. Their bodies usually measured between 1–3 inches (2.5–7.5 cm) in diameter, making them easily mistaken for a gold coin. The eyes, legs, and antennae of the goldbug lay hidden beneath its shell, lending to its appearance as a regular gold coin. When folded together, these body parts made the underside of the "coin" appear like an intentional design. The ruse was so convincing that even a thorough visual examination of the goldbug failed to reveal its true nature half of the time. However, using arcane methods or actually biting the goldbug to determine its purity would reveal its falsehood.
Goldbugs often nested with others of their kind, usually on a pile of genuine gold coins. Goldbugs waited patiently for an unsuspecting victim to pick them up. A goldbug would wait until the victim fell asleep before emerging to feed off their blood. Their bites were small and rarely woke the victim. Goldbugs fed until they consumed their own body weight in blood. They could survive for a long time without feeding, but preferred to feed daily.
If disturbed while feeding, or threatened in general, a goldbug attempted to bite its attacker and inject a deadly poison that caused nausea, dizziness, and death in some cases.