For accessing nectar, floral visitors prop themselves on one of the five flower hoods, sliding their tongues down the side of the hood where the nectar is held. They must be careful not to slip their leg down into the flower between the anthers.
|Pollina stuck to the legs of a great|
black wasp, Sphex pensylvanicus
In a study by Fishbein and Venable (1996), small- and medium-sized bees, and medium-sized butterflies had the lowest removal rates of pollinia. Their study found that it was the larger bees, like bumble bees that were most effective at transferring pollinia from one plant to the other.
|Leafcutter bee, Megachile sp. alighting|
on top of the flower hoods to nectar.
Leafcutter bees are common visitors of milkweed feeding on nectar. They rarely snag pollinium sacs so are considered ineffective pollinators.
This particular cuckoo bee is a cleptoparasite of leafcutter bees, Megachile spp. Females have a tapered abdomen ending in a sharp point that is used to break through leafcutter brood cells.
Fishbein, M., & Venable, D. L. (1996). Diversity and temporal change in the effective pollinators of Asclepias tuberosa. Ecology, 1061-1073.
Ivey, C. T., Martinez, P., & Wyatt, R. (2003). Variation in pollinator effectiveness in swamp milkweed, Asclepias incarnata (Apocynaceae). American Journal of Botany, 90(2), 214-225.
Kephart, S. R. (1983). The partitioning of pollinators among three species of Asclepias. Ecology, 120-133.