Field surveys and published data revealed that at least 42 species of insects use yellow starthistle as a breeding host in southern Europe. Twelve of these species are newly reported to feed on the plant. A high percentage of these species are in the orders Coleoptera, Lepidoptera, and Diptera and are monophagous endophages associated with the capitulum. The guilds associated with yellow starthistle in southern Europe consist of capitulum-infesting species; endophages in the stems, rosette foliage, and roots; and ectophages on leaves and stems. At least five monophagous species that attack the capitulum in different ways could potentially be used in a biological control program in the United States.