Biology

 

         Milkweed is the common name of the genus Asclepias. They're called milkweed because they secrete a milky-looking latex when damaged. Though these plants are toxic to humans, several insects use them as a food source; monarch butterflies especially, as their larvae are dependent on this plant as their only food!

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There are over 200 species of milkweed across North and South America, along with Africa. They have complex flowers with five backwards facing petals and a five-pointed corona in the middle, surrounding a gynostegium. The center of the corona hoods hold pollen sacs. Visiting pollinators can use these hoods like landing pads when coming to drink nectar. The pollen sacs then get stuck on the insect when they fly away, being carried to another flower in the process.

 

Ironically, though monarch butterflies are reliant on the plants for their caterpillars to eat, they aren't very good pollinators for them! Insects need to be large and strong enough to carry the pollen sac from flower to flower. Monarch butterflies simply aren't capable of doing that as easily as bees and wasps.