What's that smell?

January 22, 2016

After returning from Costa Rica, it’s hard to decide what to write about—there’s so much! I saw

amazing plants and animals, released baby sea turtles, made great friends, conducted research, and ate a LOT of rice and beans.

 

This first Costa Rica-themed post will focus on a particular pollinator I fell in love with: the orchid bee. There are a few different genera (types) of orchid bees that are found throughout the Americas (with the most orchid bee diversity in Costa Rica and Panama). Orchid bees are even found in Florida (they were recently introduced)!

 

The orchid bees I saw while in Costa Rica are part of the genera Euglossa. Euglossa are known for their colorful, metallic (maybe even glossy?) exoskeletons. They can be blue, green, red, gold, or a mixture of colors. (I saw the blue one but he wouldn’t sit still long enough for me to take a picture.)

 

Like honey bees, female orchid bees collect nectar and pollen for food. Unlike honey bees, male orchid bees have specialized structures on their hind legs that the bees use to collect scents. (Remember, male honey bees are pretty lazy.)

 

The more scents an orchid bee male collects, the better. Older orchid bees have more scents (as determined via chemistry) collected in their hind legs than their younger counterparts (presumably because the older bees have had more time). No one is 100% sure as to why the males do this but it is hypothesized that males collect scents to attract mates. Instead of bringing their dates a bouquet of flowers, these guys bring their dates a bouquet of scents.

 

This scent-seeking behavior is actually where orchid bees get their name. Orchids (the plants) have specifically adapted to attract these pollinators—some orchids have foregone offering a nectar reward, which is what most other pollinators are looking for—and only offer up a scent to their pollinator. These plants also exhibit tempting (to both humans and bees) scents like cinnamon, and vanilla. Sometimes, orchids even give off the smell of rotting meat, which I guess the orchid bees like?

 

To get these photos, I attracted orchid bees to a tree by placing a few drops of three different chemicals on the tree: eugenol, cineol, and benzyl acetate. All three are essential oils that are commonly found in plants. Observationally (this was not an experiment), eugenol attracted the most Euglossa orchid bees.

 

So what came first? The scent-collecting orchid bee or the smelly orchid? In 2011, scientists at UC Berkeley found that it was probably the bees. Although named for the plant, orchid bees collect scents from other sources too: tree resin, fungi, and leaves to name a few. And what’s more, the bees likely evolved about 12 million years before the orchids. Talk about playing a game of catch up.

Stay tuned for more Costa Rica-themed posts!

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