So Many White-lined Sphinx Moths!

August 23rd, 2023

Recently, there has been a huge number of large, beautiful moths observed in the gardens throughout our valley and in the surrounding mountains. I have seen this moth in previous years in my own garden at dusk when the Evening Primroses open up. This was a summer after-dinner activity, going out and watching the primroses opening, first slowly and then with a pop, they would spring open. After this, one or sometimes two beautiful, white-lined sphinx moths would arrive to entertain us more. A month ago, one of my friends sent me a video of one of the giant moths on her Echinacea cone flowers drinking the nectar during the day, then the next day I had two more people telling me they had seen this beautiful moth on a variety of flowers. I went out and checked in my own garden and there they were, at least eight sphinx moths flying around drinking nectar from a variety of flowers from Alstroemeria to Zinnia, in the middle of the day!

Since then, I have been hoping to see this impressive moth on Mitigation Lands so I could write about them in this blog but never came across them. That was until yesterday, when I captured one on camera visiting some flowers I had never seen before. This flower looked like a garden escape and was fragrant like a cross between a carnation and a rose. After checking with a local botanist and the iNaturalist app it appeared to be a plant called common soapwort in the genus Saponaria, probably Saponaria officinalis. Indeed a perennial garden escape, it is in the carnation family and originally from Europe and Asia to western Siberia. It is fitting that this plant in the valley has attracted the white-lined sphinx moths because as I researched this moth, I found out that this plant is a common host plant for it!

Here is some more information on the white-lined sphinx moth. The caterpillars of the sphinx moth are in the family Sphingidae and are commonly referred to as hornworms, like the Tomato hornworm and the Tobacco hornworm. These caterpillars have a horn-like flexible spine at the end of their body. This is probably used for defense against being eaten by birds or other wildlife. The caterpillar migrates from the host plant and digs in loose soil where it pupates about two inches from the surface and waits for spring to emerge as a moth. Their heavy body requires them to flap their wings very fast causing them to look like small hummingbirds as they hover over flowers. The hindwings are black with a reddish-pink marking in the middle. I was told there was a story circulating about a woman who saw one in England and reported a baby hummingbird had been sighted, which caused quite an uproar since there are no hummingbirds found anywhere but on the North American continent!  So why are there so many of these “Hummingbird” moths this year in Mendocino County? There are some theories being floated around but no one knows for sure. These “eruptions” have commonly happened in desert areas such as Southern California where the caterpillars have been so numerous that they have caused roads to be slick with their carcasses having been run over. If you have not seen one yet just start looking around the gardens near you that have brightly colored flowers blooming. It is likely you will spot one of the lovely, white-lined sphinx moths hovering and sipping nectar.