Picture this – It is early morning, and you are walking along a meandering path amongst the verdant foliage of a steamy Central American rainforest. Up ahead you spot a pale yellow orchid growing on the side of a large tree. What luck! You quicken your pace in excitement. As you get nearer, you notice what looks like blue and green jewels surrounding the bloom. What could that be?

Typically known for their brilliant metallic hues, orchid bees account for up to 25% of bees in the Neotropics. There are around 200 known species of these remarkable creatures spanning from Mexico to Argentina, with one species found in the USA. What makes these insects so special is their unique ecological niche and reproductive biology: They rely on orchids for their reproduction, just as orchids rely on them for pollination.

Many insect pollinators that visit flowers do so to gather nectar. Though orchid bees do get nectar from other sources for food, when orchid bees visit orchids, they are not seeking nectar. Rather, the males collect the odorous compounds, or ‘smells’, of the orchid. The types of orchids preferred varies with the species of the bee, with some species being less picky than others. These compounds are then stored in special hairs in their enlarged hind legs and used to attract mates. By being particular about the source of the ingredients, each orchid bee brews a unique ‘perfume’ of orchid smells with which to attract females of their own species. As sexual selection would demand, the males with the best ‘perfume’ blend are thought to secure the most mates. During the process of gathering the compounds, a pollen sac is deposited somewhere on the body of the bee, so that upon visitation of subsequent flowers, voila – pollination occurs! What a beautiful, highly unusual example of mutualism. Of course, when two organisms are so closely entwined, trouble for one inevitably spells trouble for the other.

Orchid bee Eufriesea mussitans with pollen sacs stuck to his back.

There is a lot of evidence to suggest that orchid bees are fairly resilient to changes to their natural habitat, such as forest fragmentation. Orchids, however, are disappearing more and more from rainforests due to deforestation, poaching and the effects of climate change. This means that orchid bees are also threatened, especially those that are more specialized to a certain species or group of orchids. Orchids and orchid bees that are ephemeral, or only around for very short periods based on season, are perhaps at the highest risk. This is because fluctuations in rain patterns and temperature can disrupt the orchids, which in turn impacts the bees that rely on them. An example of this is how the appearance of species within the genus Eufriesea, a larger, generally less vibrant group of orchid bees, occurs at the same time as the ephemeral Stanhopea genus of orchids. These orchids appear for just a few weeks during the rainy season, with the individual flowers being in bloom for only 3-4 days. This correlates with the sudden and massive boom of Eufriesea populations. Major shifts in historic rain patterns are already being documented by locals in Costa Rica and other places in the Neotropics, and as climate change progresses these shifts will only become more pronounced and damaging to flora and fauna such as orchids and orchid bees.

Though they have gotten more attention than many other groups of insects in the tropics, there is still so much more to learn about them. There are many regions across their range where they have not yet been researched, and we know very little about their nesting habits. The females of several species have never even been described, as they are not attracted to baits meant to mimic the ‘smells’ of orchids, and tend to be even more allusive than the males. Without action against climate change, deforestation, and poaching, we may lose this charismatic pair before these questions can be answered.

References

Botsch, J. et. al. 2017. Impacts of forest fragmentation on orchid bee (Hymenoptera: Apidae: Euglossini) communities in the Choco biodiversity hotspot of northwest Ecuador. J Insect Conserv 21:663-643.