Orchid Bees: fragrance gatherers

A green Euglossine bee, Euglossa spp.

A green “orchid bee”, Euglossa spp.

Neotropical orchid bees (or euglossine bees) are characterized by their very long tongues and by a unique behaviour of males. Male orchid bees collect scents from all sorts of fragrant objects, including flowers, tree wounds, decaying wood, and faeces, and store them in specialized hind leg pockets. So, rather than gathering pollen and nectar from flowers, like most bees do, orchid bees gather chemical fragrances – presumably to make ‘perfumes’ to attract a mate. The perfumes are hypothesized to serve as indicators of male quality (viability, survival) and are judged by female bees prior to mating. I guess perfume-making is pretty romantic, for a bee…

Encircled in red is the specialized hind leg pocket (Hind Tibial Organ), or  an Euglossine bee.

Encircled in red is the specialized hind leg pocket (Hind Tibial Organ), of an Euglossine bee.

Now, let’s go through the fragrance collection process! Males use an intricate “conveyor belt” mechanism for fragrance collection and concentration. What is meant by this, is that fragrances are initially collected by “brushes” on the forelimbs, and then sequentially transported limb-to-limb, all the way to the specialized hind leg pockets (see  below). Here is a video depicting fragrance collection, the orchid bees take to the wing when transferring fragrances:
http://www.youtube.com/watch?v=JeL9cI4N_1A

The “conveyor belt mechanism” by which Euglossine bees collect and concentrate fragrances in their hind tibial organs.

This fragrance collecting behaviour is crucial to the survival of many orchid species, as some orchids do not produce nectar (as nectar is a typical reward for pollinators, non-nectar producing orchids reward orchid bees with fragrant compounds instead). At least 197 species of orchids are exclusively pollinated by male Euglossine bees! So not only is this behaviour incredibly cool, but it’s also extremely important!

Catasetum atratum, one of many beautiful species of orchid that is exclusively pollinated by male Euglossine bees.

Catasetum atratum, one of many beautiful species of orchid that is exclusively pollinated by male Euglossine bees.

Important notes:
1) Orchid bees do not exclusively pollinate orchids; they pollinate other flower families, too.
2) Not all orchid bees are a metallic green; some species are a metallic blue or gold, other species aren’t metallic at all.
3) Not all “orchid bees” make perfumes, some are kleptoparasitic of other orchid bees!
4) Fun fact: one species of orchid bee was recently named Euglossa bazinga – after Dr. Sheldon Cooper of the Big Bang Theory!

Two Euglossine bees on a passionflower.

Two Euglossine bees on a passionflower (Passiflora spp.).

Further reading:
http://homepage.ruhr-uni-bochum.de/thomas.eltz/tibmorE.html

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