Cassida

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] has been used as a biological control agent against Canada thistle.
The genus name is derived from Latin Cassis for a metal helmet.
There are at least 430 described species in Cassida. This genus contains the most species of all Cassidinae. Larvae build shields with their feces and exuviae, a widespread pattern of tortoise beetles.