Head-clipping Weevil - Haplorhynchites aeneus
Commonly known as the sunflower head-clipping weevil, this destructive pest clips flower heads from other plants as well.
Live adult weevils photographed in the wild at Blackwell Forest Preserve, DuPage County, Illinois.
Size: 10mm

 

Head-clipping Weevil
Adult Female Head-clipping Weevil, Haplorhynchites aeneus

Adult weevils girdle flower peduncles and leaf petioles leaving partially severed flowers or leaves hanging on the plant. It is thought only the female weevils engage in girdling, but both genders then congregate inside the now-upside down, partially opened flowers, to feed on pollen, mate and lay eggs.

Weevils expend a lot of time and energy in this clipping behavior. It may function to reduce the suitability of the plant for other flower-feeding insects that otherwise would compete with the weevil and its larvae for resources.

The eggs hatch only after the flower heads drop to the ground, where the larvae feed on the decomposing plant tissue before overwintering in the soil. Pupation and adult emergence occurs the following summer, timed to correspond to the sunflower's entering its flowering, reproductive phase. [1]

Head-clipping Weevil
Weevil at stem girdle

Camera Location

41° 49' 53.32" N, 88° 10' 35.49" W

Find the location on: Google Maps - Google Earth

Weevil Damage
Weevil Damage: Clipped flower Heads. You can just see a weevil hiding in the yellow flower, lower center.

Head-clipping Weevil

Insects  in the subfamily Rhynchitinae are commonly known as "tooth-nosed snout weevils." The teeth at the tip of the snout are clearly visible in the above photo. The weevil is sitting atop a clipped sunflower head.

References
  1. J.P. Michaud, Kansas State University Entomology, Sunflower Head clipping Weevil, Haplorhynchites aeneus