Sunflower head-clipping weevil

 

Female head-clipping weevils (Haplorhynchites aeneus (Boheman), Coleoptera: Curculionoidea: Attelabidae) make a ring of punctures on the peduncle below a flower, which causes the peduncle to break. Then both partners move to the drooping inflorescence, mate, and the female oviposits in the head. The flowerheads eventually fall to the ground where the larvae continue to feed in the head. Most other inflorescence insects in our system have to drop to the ground individually.

H. aeneus became our first official lab mascot because we spend a lot of time clipping sunflowers ourselves. As a bonus, H. aeneus eliminates around 15-20% of the heads in our studies, making data collection more reasonable in an experiment with several thousand inflorescences.

Sunflower seed weevils

Gray seed weevil damaged seeds	Red seed weevil damaged seeds

Two species of seed weevils feed within sunflower achenes in our study area.  The first is the gray sunflower seed weevil, Smicronyx sordidus LeConte.  The adults are usually found on flowers in the bud stage.  Larvae develop within individual achenes.  Damage by the gray seed weevil is readily apparent as the larvae gall the seed, resulting in a seed that appears bloated and is much larger than undamaged seeds.  Larvae chew an exit hole near the top of the side and drop to the ground to pupate and overwinter.

The second species is the red sunflower seed weevil, Smicronyx fulvus LeConte.  Adult red seed weevils can be found among the florets of open inflorescences, feeding on pollen and developing seeds.  Larvae develop within individual achenes.  Damage by the red seed weevil larvae is more difficult to spot because the larvae do not change the seed morphology.  Instead, an exit hole is seen on the side of the achene near the top when the larva is ready to leave the seed and drop to the ground.