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Tortoise Beetles - Deloyala clavata /
Helocassis clavata
and Cassida rubiginosa Order Coleoptera - Beetles / Family Chrysomelidae - Leaf Beetles / Subfamily Cassidinae - Tortoise Beetles Live adult tortoise beetles photographed at Winfield, Illinois. Size: clavate: 7mm not including antennae / thistle: 10mm |
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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. |
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 Clavate Tortoise Beetle |
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Ever since I saw its picture in the Audubon Society's Field Guide, I'd wondered what this "clavate" (meaning, essentially, "thickened at one end") really looked like (their pictures are terrible). I finally saw one on May 22, 2005, then: a mini - population explosion in a patch of wild morning glory. Oh boy. These little guys don't do much that I can tell. They mostly sit around, flattened against the bottoms of leaves, grinning, looking all the world like bits of snot with general goo mixed in. I have not figured out which end is supposedly thickened. I did find a few willing to get up and walk about - but they never go far without suddenly bursting into flight. And I do mean suddenly; you can't catch them unfurling thier wings, BOOM - they're gone - a few inches away. You be the judge of what evolution was thinking when it spat out these little gems. |
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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.
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