Photo of the Week

Knapweed Seedhead Weevil
Knapweed Seedhead Weevil
Larinus obtusus, Curculionidae
Enderby Mabel Lake Road, British Columbia, Canada
Nikon D5100, 105 mm f/2.8
July 13, 2014

This week we have another photo (mouse over for a dorsal view) from my recent family trip to the Okanogan. My Dad has a keen interest in weeds both as an active member of the naturalist community in Alberta and more recently in his capacity in his summer job as a weed control technician. He quite upset by the weedy state of the Okanogan. I was able to offer him some comfort by telling him that the Spotted Knapweed was being controlled somewhat by biocontrol agents like this Knapweed Seedhead Weevil. Knapweed is controlled by a suite of biocontrol agents which includes two similar and closely related weevils whose larvae feed on the seeds of Knapweeed. These two seedhead weevils are Larinus obtusus and L. minutus and their preferred hosts are Spotted Knapweed and Diffuse Knapweed respectively. One character that can be used to differentiate these weevils is leg color, with L. minutus having a reddish brown cuticle and L. obtusus having black cuticle with reddish brown highlights near the leg joints.

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