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The leaf beetles (family Chrysomelidae) generally have
antennae 1/2 their body length or less, and are characterized by their
bright metallic colors. The adult beetles feed on leaves and flowers;
the larvae attack roots, eat leaves, or tunnel within them. Many beetles
of this family are important agricultural pests. There are roughly 1,400
species in North America.
Habitat: Meadows and forest clearings, roadsides.
Cassida rubiginosa is commonly known as the "Thistle tortoise
beetle" - larvae and adults feed mainly on several species of thistle
(Carduus, Cirsium, Onopordum spp.) plus knapweed (Centaurea spp.) and a
few other weedy composite plants. This is an invasive species, native to
Eurasia; accidentally introduced in Quebec in 1901, has since spread
east to New Brunswick, west to Alberta, and south to the northern United
States. This beetle is said to have been used in biological control of
thistles. (These specimens were photographed on bull thistle Cirsium
vulgare). |