A Meal and a Warm Place to Spend the Night

Plants in the genus Philodendron are native exclusively to the warm tropics, and usually in moist or rainforest environments. Their blooms are often large but not particularly conspicuous as blooms go. In my own plant collection, I've seen a number of species bloom but have never seen a pollinator (other than myself) visit them. A little research, however, revealed to me that they do have pollinators, even if the critters are not native to the United States. The surprise was that the pollinators are various species of beetles, not bees or wasps.

The plants have several interesting means for attracting these insects, too. I've observed a minimum of three possible attractants; the aroma emitted by the inflorescences, the significant heat given off by the bloom when it is receptive, and the presence of sterile parts of the inflorescence that are edible and nutritious to the pollinators. For the beetles, this is equivalent to being offered a free meal and a warm place to spend the night! Why spend the night, however? Because these blooms become receptive to pollination in the early evening, and they also release their pollen at about the same time. Beetles in the genus Cyclocephala have been observed engaged in activity within some Philodendron blooms, with this activity resulting in pollination. So let's look in on the action and see what's going on.

All Night Long!

This is not just a flyby, as is often the case with bee pollination. Rather, the beetles remain a number of nights, and continue from one inflorescence to another. Like most parties, the festivities begin in the early evening. Beetles arrive at that time when the inflorescences are heating up and emitting their characteristic aroma. They enter and, perhaps due to the heat, aroma, and presence of both sexes, begin mating and feeding on the sterile male flowers.

By sunrise, the beetles settle down, resting in the lower chamber of the bloom. An examination of the interior of the bloom at this time reveals the presence of beetle offal scattered about. The next night, the beetle fun resumes, but this time their host signals to them that it is time to pack up and leave. One can imagine at this point that the host has decided that the beetles have worn out their welcome and left such a mess that the party is over. This is done by the gradual closing of the bloom, essentially squeezing the beetles out of their temporary abode. Any beetles too slow at leaving can get crushed by the force of the thick closing spathe around them. As they exit that night, they have to walk through sticky resin and stringy pollen chains, loading them up for their next stop at a female-receptive bloom. In this way the beetles party from bloom to bloom, pollinating them as they go along. Logically, the very first blooms to open will not get pollinated, as the beetles arriving there first have not visited any other blooms prior to their arrival. Instead, these first inflorescences provide the pollen load for the second wave of blooms to open.

So next time you attend a party featuring "The Beatles", you might remember the Philodendron parties with "The Beetles"!

Image credit: LariAnn Garner