Here’s a thing you might not know about the “mutualistic” interaction between plants and their pollinators. The truth is, both partners are seeking to gain a benefit from the interaction, and they often take advantage of each other. For pollinators, taking advantage can mean nectar robbing or stealing pollen without pollinating.
For plants, taking advantage means attracting pollinators without providing a reward. This is called floral deception, and orchids are masters of it. Ideally, they can attract a specialized pollinator without investing in expensive rewards like pollen and nectar. But if they want a pollinator to carry their pollen without being able to eat it, they need a pretty clever trick.
And this is what they have come up with! It’s called a pollinium, and it’s a mass of pollen grains all in one sticky package. When bees visit orchids* for whatever reward they’re expecting to get (be it scent, nectar, or even a mating opportunity), they step on a trigger within the corolla, and a lever swings around and delivers the pollinium to a species specific location on the bee’s body. The pollinium sticks there because of a viscidium, a special sticky place like a glue dot that adheres somewhat permanently.
So here are some photos of Euglossa bees carrying pollinia:
*Some other plants do this too…a familiar example is the Milkweeds (Asclepias)