Milkweed flowers have a unique anatomy.

5 fused anthers and stigmas form a central "corona" atop 5 reflexed petals.

Pollen are packed into sacs called "pollinia"; pairs of pollinia hang like saddlebags within stigma chambers.

Hidden within the corona are also anther slits to receive pollinia.
 
  A pollinating insect, such as this Eastern Carpenter Bee visiting a Garden Phlox, often gets its legs trapped in the anther pockets.

When she pulls her legs out, the pollinia are carried off, and may drop down the anther slit of another milkweed blossom, thus achieving pollination.
 
  The pollinia burden can be quite heavy; this bee rests awhile with her luggage.

Bald-faced Hornets may also be an unwilling pollinator.
 
  Sometimes a Honey Bee fails to free her legs and becomes permanently trapped, eventually dying of dehydration.

Other pollinators such as Lesser Maple Spanworm Moth can also become trapped.

The milkweed nectar is so fragrant that insects are willing to risk life and limb harvesting the liquid, each intoxicating step potentially their last.
 

Honey Bee trapped in slits

Other visitors to milkweeds include:
Milkweed Tussock Moth
 
Red Milkweed Beetles
 
Large Milkweed Bugs
 
Great Golden Digger Wasp
 
Hummingbird Clearwing
 

HomeCC BY 4.0 Peter Chen 2.0