Species Cassida rubiginosa - Thistle Tortoise Beetle

Bloody-nosed Beetle, Thistle Defoliating Beetle

Cassida rubiginosa Müller 1776

Latin rubiginosus 'rusty/rust-colored'; supposedly refers to the beetle's ability to secrete a reddish liquid from its head, giving rise to its other common name of Bloody-nosed Beetle [source: anon.]

6-7.5 mm

Adult: dorsum green in live individuals, fading to brown/yellowish in dead specimens; small double depression in surface of each elytron midway along anterior margin, usually marked by two dark spots, or sometimes with more extensive dark shading; anterior margin of both elytra collectively forms a very shallow concave arc when viewed from above - shaped more like a rounded bracket than a brace bracket; medial and inner areas of each elytron covered with small punctures but not deeply pitted; venter completely black; femora black; tibiae and tarsi brown or brownish-orange

Larva: oval, brownish or greenish, with dark branched spines around perimeter, and a forked tail spine on which it accumulates moult skins and excrement held as a protective parasol over the insect's back

n. US & Canada, native to the Palaearctic Region(1); accidentally introduced in PQ in 1901, and spread since east to NB, west to AB, and south to n. US(2); intentionally introduced to VA to control thistles [map:(3)]

weedy fields and waste places where food plants grow

larvae and adults may be present from spring through fall

various Asteraceae, incl. thistle (Carduus, Cirsium, Onopordum) and knapweed (Centaurea) spp.(1)

described in great detail in(2)

one generation per year; overwinters as an adult in soil litter; beginning in spring, up to 1,000 eggs are laid on the underside of leaves in cycles of approximately 6 weeks, with 7-week rests; adult life span is about 80 weeks, with an egg to adult developmental period of 6 weeks. The larvae carry a fecal shield as protection against predators.

used in biological control of thistles, but the impact is usually restricted by parasitoids; not approved for biological control because it feeds on several native and economically important thistle species(4)

Fact sheet - D.W. Pierce, WSU Extension (4)