A tuft of dog hair in the tree? No, the tangle is walking, hair a-tremble.

A closer look: legs, head, and puckered skin dotted with hair-nozzles.

These photos are old — from a few weeks ago — not not so old that the 1980s might serve as an excuse. Instead, these waxy locks are mouth-gumming defenses, reminiscent of my favorite aphid (oh the choice was hard), the boogie-woogie beech blight aphid. This is no aphid, though, nor a caterpillar, but a sawfly larva, the leaf-chewing life stage of Eriocampa juglandis, the “Butternut Woollyworm.”

Sawflies are wasps, not flies (Symphyta, within the Hymenoptera, for those playing ento-bingo). The “saw” in their name comes from the serrated ovipositors that the females use to lay their eggs inside plants. Eriocampa females oviposit in the midrib vein of the leaf, using the blades on the tips of their abdomens to pierce the plant and nestle sawflies-to-be in a bed of food. After an egg-laying female is done, the midrib looks like an evenly-stitched hem, punctured by two dozen or more regularly-spaced holes.

The young sawflies chew holes in leaves, often working in teams lined at leaf margins. Only when they reach their older years, after several molts, do the larvae grow their fabulous hair-dos.