|A Bee Carrying Milkweed Pollinia|
Notice the pollinarium that is attached to the middle leg of this bee. You can see the two packets of pollinia and the filament snagged on the bee's leg.
Bees are strong fliers so they mostly can free themselves, but some insects aren't so fortunate like the one pictured below.
Many insects love milkweed nectar. Despite a few insects becoming ensnared by the pollinarium, many visiting insects end up with extra baggage and plenty of the pollinia reach the milkweed's stigmas and the pollen accomplishes its purpose of fertilization.