Friday, February 5, 2010

Bumblebees and Turtleheads

Some flowers are easy to pollinate, wide open, with free access to pollen and nectar; an insect with no skills and no elaborate equipment can collect food without difficulty. Other flowers make things interesting; their pollinators have to figure out how to enter them and how to reach the hidden rewards. It is great fun observing the labors of some bumblebees visiting one of these "difficult" flowers.

Last summer my friend's garden was brimming with turtleheads and the turtleheads were brimming with visitors, not a great variety (I only saw bumblebees) but a large number. This flower deserves its name, it looks like the head of a turtle, with powerful jaws and a large cavity inside, where the nectar is hidden and where the important parts of the flower lay, the male parts which carry pollen and the female parts, which receive the pollen and produce the seeds.

Young flowers, like the one above are not quite ready for visitors and clench their jaws tightly. This bumblebee tried in vain to enter the blossom and never got more than its head inside so it gave up the effort and tried a different one.

The next flower must have been just right, the entrance was slightly open, and this time it entered without difficulty and spent several seconds out of sight collecting whatever reward it could find, perhaps just pollen or nectar, more likely both.

The fun started when it tried to leave the same way it came. It kept backing up but, no matter how hard it tried, it just couldn't get out tail first; so it went deeper inside to make a U turn; out it came, head first and briskly flew away.

It promptly learned the way in and the way out and when it entered other flowers it turned around without hesitation and emerged head first. Interestingly, in some cases it entered the right side of the mouth and left through the left. Not all flowers were so hard to exit; some, maybe older ones had loosened their jaws a little further, the mouth stood agape and bees came and went with no difficulty and no need to turn around. You can see it all in a video.

It makes you wonder why bumblebees persist on visiting difficult flowers and why flowers make things difficult for their pollinators. From the point of view of the flower, it must be advantageous to select its clientele, allowing only those with the right equipment (e. g. a long tongue, powerful muscles, the correct size) and with enough intelligence and memory to figure out what to do. In this way they ensure that their pollen gets carried to other flowers of the same species and doesn't get wasted on different flowers.

To satisfy the demands of such a clientele the flower has to offer the right incentives. So, such flowers are likely to yield large amounts of nectar, richer pollen or both. Thus, the reasons for a bumblebee to visit such flowers become obvious; it is worth the extra effort if the recompense is far superior to the one offered by plain, easily accessible flowers.

Bumble Bees, the Pandas of the Insect World

List of articles

© Beatriz Moisset. 2011

No comments:

Post a Comment