Life Cycle:
Over Wintering Stage:  Winters as adult beetle in the litter or in the soil cracks near the host plant.
Egg Stage:  They are laid among the inner florets (central area) of newly opened flower.  They hatch 3 days later at about 77 degrees F.  The eggs are yellowish in color, and range from an oval to a round  shape and measures 0.05 in. long to about 0.03 in. in width.  There are up to 5 eggs in a cluster, but a female lays between 28 and 130 eggs (1).  They develop between June and September. (3)
Larval Stage:  Feed in the seed head on pappus hairs and developing seeds.  They are fully developed in about 17 days. (5)
Pupil Stage:  Pupation happens in a chamber constructed from seeds and pappus hair.  They develop over 9 days. (5)
Adult Stage:  After the pupil stage the beetles chew their way out of their chamber.  Their wintering state stops at the end of May, and they reach peak population in July.  The 1st generation of beetle attacks seed head in late July and August.  They are black in color with yellow hair on back and they range from 0.2 in. to 0.28 in. in length. (5)

Damage to Host:  1-2 larva can destroy the seeds in a seed head.  Larva can consume the entire content of immature knapweed seed heads, including the seeds, florets, and portions of the receptacle.  They can also cause gall-like structures in the seed head causing the plant's resources to be further depleted.  They destroy nearly one-hundred percent of the seeds in infected seed heads.  Adults feed on the leaves, stems, and florets but prefer flower heads when available. (5,4,1)

Plant Species:  They like spotted knapweed best but also feed on diffuse knapweed.  (5)

Location:  They like moist areas but will adapted to any area knapweed grows. (5)

Host Impact:  Will reduce seed production and plant heath. (4)

Release Habitats:  Will develop anywhere there is a good source of food. (5)

Collect, Transport, and Release:  To collect and transport just sweep for adults or collect seed heads in July to August.  Place them in a suitable insect container (such as a paper ice cream container) and transport them in a cooler with an ice pack. (3)

Purchase: Unavailable foe purchase at this time. (5)

Info:  They were first released in 1993 in the U.S.  They have been recessed in Idaho, Minnesota, Montana (established), Nebraska, Oregon, and Washington (established). (3)

2. Knapweed Weevils [online] Unavailable:  http:// cofcs66.aphis.usda.gov/oa/knapweed.htm  Sept. 3, 1999.

3. Division of Plant Industry  Biological Pest Control Section, Spotted and Diffuse Knapweed
 Biological Control Plan [online] Available:  http://www.ag.state.co.us/DPI/publications/knapweed.html
 Sept. 3, 1999.

4. Biological Control- Stop/ Diffuse Knapweed, USDA,  Dec. 1994.

5. Rees Norman, et. al, Ed., Biological Control of Weeds in the West, Weston Society of Weed Science, in cooperation with USDA, ARS, Mt, Dept. of Ag, and Mt State Univ., Color World Printers, Mt, Fed., 1996.