Woolly alder aphids (photo by Bob Lepak, Bugwood.org)

19 October 2026

Until the first killing frost woolly alder aphids (Prociphilus tessellatus) actively coat alder branches like fluffy white socks. I found some in late September 2020 but didn’t know what they were. This month a group of birders found them at Yellow Creek State Park and Ed Donley shared the bug’s identity with the group at Buckeye Yard & Garden Online: Woolly Alder Aphid.

Named for their host tree, woolly alder aphids (Prociphilus tessellatus) are similar to beech blight aphids (Grylloprociphilus imbricator) — the ones that do the boogie-woogie. However, alder aphids don’t move when frightened. Instead they just stay in a tight cluster.

The woolly protection comes from structures on the bugs’ backs that are arranged in a block pattern. You can see the pattern on these nymphs who haven’t fully exuded / unfurled the wool.

Woolly alder aphid nymphs (photo by Bob Lepak, Bugwood.org)

These aphids suck phloem sap from alder trees and excrete a sweet “honeydew” that attracts harvesters such as carpenter ants and adult green lacewings.

Carpenter ants harvesting honeydew from woolly alder aphids (photo from Wikimedia)

Green lacewing adult (photo from Wikimedia)

Green lacewings have a dual purpose at the aphid cluster. The adults eat the honeydew and the females lay eggs (on “poles”) near the aphids. Lacewing nymphs are carnivorous so the eggs are placed among future food.

Lacewing eggs (photo from Wikimedia)

The honeydew also attracts mold which turns it gray/black.

Aphids are white. The black material is black sooty mold Scorias spongiosa (photo by David Stephens, Bugwood.org)

It would be fascinating to watch a woolly alder aphid cluster go through these phases, but it will have to wait until next summer when the next generation of aphids hatches.

Meanwhile watch beech-blight aphids do the boogie-woogie in the video embedded in this vintage article.