Cassida

thumb|Cassida vibex thumb|Cassida azurea

Cassida is a large Old World genus of tortoise beetles in the subfamily Cassidinae. The natural history of Cassida sphaerula in South Africa is a typical life cycle. Several species of Cassida are important agricultural pests, in particular C. vittata and C. nebulosa on sugar beet and spinach. The thistle tortoise beetle (Cassida rubiginosa) has been used as a biological control agent against Canada thistle.