Carpenter Bees Buzzing Pollen

I’ve been keeping watch on the Evening Primrose to find out what insect is responsible for pollination and have finally found a likely candidate.  There have been no late night moth visitors, but I’ve seen a lot of early morning Carpenter Bee activity.

Pollen grains on the body and legs of the bee suggest effective transport of pollen between flowers.  This is what you would expect from a bee.  The unusual aspect is the method in which the Carpenter Bee collects that pollen.

The bee lands on the flower, but it doesn’t stay there.  Immediately after setting down, the bee crawls on over the flower and begins moving down the stem.  The trip across the flower is the maneuver that deposits pollen.

At a point on the stem just below the flower, the bee gets itself carefully positioned.

Then it hugs tightly to the stem and vibrates, an action known as buzz pollination.  The pulsations from the vibrating bee cause the pollen grains to fall from the flower’s anthers.

In some types of flowers the pollen falls onto the bee.  I’m not sure the shape of the primrose bloom allows much of the pollen to fall free of the flower, so buzz pollination wouldn’t appear to be the best strategy for this species.  The fact that the method is working for both bee and flower suggests that I don’t know everything there is to know about pollination methods.  Animals do what they do because it works.  I shouldn’t be second guessing their actions.  

Evening Primrose

A Common Evening Primrose, Oenothera biennis, managed to establish itself beside the barn.  This is a native biennial that prefers growing in areas of bare, disturbed soil.  I always let one or two grow to maturity each year.  The seven foot tall plants produce an abundance of pretty flowers, but you have to be an early riser to see them at their best.

Evening Primrose is a night bloomer.  Flowers open in late evening and wither in the early morning sunlight.  Sphinx moths are common night time visitors to this flower.  I’ve spent several nights out watching and have yet to see any insect come near the flowers.  I haven’t stayed out all night, but there should be some nectar hunters out in the hour on either side of midnight.

In years past, I’ve seen plenty of sphinx moths at these flowers.  This year’s flowers seem to be incredibly lonely.  I wonder if the sphinx moths have gone the way of my missing butterflies.

Within a few hours after sunrise, the flowers have faded away.  The flower stalk keeps producing more flower buds.  There are always a few new buds ready to open every night, so the actual blooming period lasts for quite a while.  Old flowers are busy developing seeds.  Something must be fertilizing the flowers, because the seed pods just keep growing.

Ants have claimed this plant and have created a temporary nest at the base of the stem.

These small ants are on constant patrol and can be found everywhere on the plant.

Several Spittlebug nymphs are residing on the plant.  Most make their foamy nest near the stem on the upper side of the leaf.





Nymphs stay safely hidden within their bubble nests and feed on sap from the primrose. Each foamy mass contained at least two nymphs.  This is a dorsal view of two nymphs.  The right hand nymph is oriented head down and the left is head up.

The nymphs crawl free of their nest to perform the final molt into adulthood.  The adults are capable of flight and take off to pursue a free roaming life style.

The foam is apparently a tasty, but dangerous treat for many insects.  This ant and fly seem to have gotten stuck and perished in the sticky substance.  Even if the Evening Primrose didn’t have such nice flowers, the insect interactions alone would be worth having a few of the plants around.