October through mid-November is the typical flowering time for Witch Hazel. The last of the blossoms of this fall-blooming shrub can still be seen in parts of the Northeast. Its long, bright-yellow petals and the presence of a sweet-smelling nectar tell you that Witch Hazel flowers are pollinated by insects. However, there are very few insects present this late in the year and its pollinators have been elusive to the human eye. With the exception of syrphid, or hover, flies, I have never seen any insects visiting these flowers.
It turns out that I was observing them at the wrong time of day. Naturalist Bernd Heinrich discovered that a group of owlet moths called winter moths are active on cold nights and regularly visit Witch Hazel. These moths have the ability to heat themselves by using energy to shiver, raising their body temperatures by as much as 50 degrees in order to fly in search of food. Solved is the mystery of what pollinating insects are still active this late in the year!
Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.
Adult hover flies, often referred to as syrphid (family Syrphidae) or flower flies, feed on pollen and nectar, and are often seen hovering at or crawling on flowers. Many have black and yellow bands on their abdomen, and are frequently mistaken for bees. There are certain species of hover flies that mimic stinging wasps, including yellow jackets and bald-faced hornets (see photo). Predators such as birds, ambush bugs, and spiders might think twice about eating an insect that can sting, and hover flies take advantage of this. The process through which this occurs is called Batesian mimicry, and refers to when a harmless species evolves to imitate a harmful species that has the some of the same predators.