he seed weevil was first released in Australia 1992. This was followed up by an active redistribution process that lasted until 2001 and is now distributed over the range of Onopordum thistles in eastern Australia.
Adult weevils are large, up to 20 mm long and 10 mm wide. They are black, and young adults are covered with a yellow waxy coating. This coating gradually wears away so that older weevils become increasingly black. Females lay up to 60 eggs on the thistle flower heads, and these can be recognised by the brown caps of faecal material (fras) placed over the eggs by the females to protect them. The large white larvae remain inside the flower head and are normally not visible.
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<table style="border:1px solid;padding:2px; width:310px;" ><tr><td><a href="https://www.scienceimage.csiro.au/image/3209/"><img src="https://www.scienceimage.csiro.au/images/embed/300_200_BE3694.jpg" width="300" alt="An adult Thistle Seedhead Weevil on a Scotch thistle head." style="margin: 0 0 5px 0; border: 0px;"></a><br/><a href="https://www.scienceimage.csiro.au/image/3209/">An adult Thistle Seedhead Weevil on a Scotch thistle head.</a><br />by CSIRO</td></tr></table>
An adult Thistle Seedhead Weevil on a Scotch thistle head.