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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, pollen loss and movement on the proboscises of Manduca sexta (Sphingidae) hawkmoths was experimentally measured. It was predicted that (i) proboscis curling causes pollen loss; (ii) pollen that is not lost is displaced from its deposition site; and (iii) repeated curls result in more displacement. Pollen from Datura wrightii, an important nectar plant for M. sexta, was placed distal to the knee bend on M. sexta proboscises, and the number and location of grains was recorded after proboscis curls. 3. Consistent with the hypotheses, proboscis curling caused significant pollen loss. (i) A single curl resulted in the loss of almost 75% of the pollen from the placement site; after repeated curling, 98% of grains were lost from this site. (ii) A single curl was also sufficient to displace pollen across all surfaces of the proboscis, but (iii) further curling did not affect its distribution across surfaces. 4. Together, these results suggest that precise pollen placement on the proboscises of hawkmoths would be unlikely to increase pollen transfer success. Strategies by which flowering plants might mitigate the effects of pollen loss from visitors with flexible pollen-pickup structures are discussed. 

Abstract Sex‐associated differences in behavior can have large ecological consequences, especially in plant–pollinator communities where floral visitor behavior affects plant reproduction. Whether these differences are prevalent enough to impact community‐level processes, however, is unknown. Using 256 plant–pollinator communities, we built networks where the floral interactions of each sex were modeled separately, comparing observations to simulated networks where sex was randomized. We found that (1) in many species the sexes differed in their network roles and visited different partners, with females tending to visit more species and more peripheral species than males; (2) more generalist species differed more in network roles between the sexes; and (3) networks where nodes were separated by sex were more specialized than simulated networks, but were similarly resistant to perturbations. These findings suggest that despite variation among species, sex‐associated differences in behavior are large enough to impact the network roles of male and female pollinators and common enough to influence the interaction patterns of entire plant–pollinator communities.