The Lygaeidae are a family in the Hemiptera (true bugs), with some 60 genera in six subfamilies. The family includes the insects commonly known as milkweed bugs, and also some of those known as seed bugs. The family used to be vastly larger, as numerous former subfamilies have been removed and given independent family status, including Artheneidae, Blissidae, Cryptorhamphidae, Cymidae, Geocoridae, Heterogastridae, Ninidae, Oxycarenidae, Pachygronthidae, and Rhyparochromidae, which together constituted well over half of the former family. Many of the species feed on seeds, although some feed on sap (mucivory), and a few, such as the wekiu bug, feed on insects.
The bizarre and mysterious beetle-like Psamminae were formerly often placed in the Piesmatidae, but this is almost certainly incorrect. Their true affiliations, however, are not entirely resolved to satisfaction.