Proboscis curling in a pollinator causes extensive pollen movement and loss

1. Precise pollen placement on floral visitors can improve pollen transfer, but in many plant species, pollen is deposited onto the flexible proboscises of long-tongued insects. These proboscises are curled and uncurled between floral visits, potentially causing pollen to be lost or displaced. Rates of pollen movement and loss resulting from proboscis curling, and hence the potential quality of long-tongued insects as pollinators, are unknown.

2. Here we experimentally measure pollen loss and movement on the proboscises of Manduca sexta (Sphingidae) hawkmoths. We predicted that 1) proboscis curling causes pollen loss; 2) pollen that is not lost is displaced from its deposition site; and 3) repeated curls result in more displacement. We placed pollen from Datura wrightii, an important nectar plant for M. sexta, distal to the knee bend on M. sexta proboscises, and recorded the number and location of grains after proboscis curls.

3. Consistent with our hypotheses, proboscis curling c...