On warm, sunny days in November snow is unexpected, yet, often a flurry of white specks swirls in the gentle breeze. Closer inspection reveals the specks are not water crystals, but tiny flying insects with fluffy white abdomens. The flies congregate in airborne masses, slowly circling one another. The show is not for us, it is a sexual display designed to entice fellow aphids. The fuzzy fliers are woolly alder aphids, Paraprociphilus tessellates, and if you’re not careful to keep your mouth shut when walking outside, you may swallow a few. They swarm in huge numbers, doing their mating dances.
These aphids can also be seen in white masses of fluff on the trunks and branches of alder trees. The aphids live in large communities and excrete a waxy white substance that protects them from predators. I suspect it also helps waterproof and insulate them. During the time the immature aphids are feeding on tree sap, they move little and the wax from their bodies joins together to form a dense protective coating.
The woolly alder aphid reproduces asexually during the warm months. Only wingless females are hatched, clones of their mothers. As cool weather approaches, a generation of winged, sexed aphids, alates, occurs. The males and females drift in the air, finding a mate. They move to silver maple trees where the female deposits one egg on the underside of a leaf. In the spring the egg will hatch and the nymph will feed on the maple leaf until it can move to an alder tree and join with a community of aphids. By reproducing sexually, the aphid species is able to mutate DNA to adapt to changes in environment that clones would not survive. For such tiny specks of white fluff, these insects lead very complicated lives. Their dependence on two tree varieties makes them susceptible to habitat loss from disease or human tree clearing activity. Luckily, the alder is a persistent, hardy, and fast growing species of wetland shrub and the silver maple is beloved by humans for it’s decorative appeal. So, the little woolly alder aphid should have no worries.
Yes, life is a bowl of tree sap for the aphids. They drink the sap and produce a sweet, moist, waste secretion called honeydew. Protective ants milk the aphids for their honeydew and defend their food supply, keeping predators away. Since the aphids do little discernible harm to either tree species they parasitize, they are not eradicated by humans.
These lucky little balls of fuzz have got it made and we are destined to enjoy many more autumnal faux snow flurries from them.