Thistle Tortoise Beetle (IMAGE) Max Planck Institute for Chemical Ecology Caption As its name suggests, the thistle tortoise beetle (Cassida rubiginosa) feeds on thistle leaves. Its favorite food plant is the field thistle, a dreaded weed in agriculture worldwide. The thistle tortoise beetle, which is considered an important herbivore of the thistles, is used in biological control of the weed. Credit Hassan Salem, Emory University. Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.