The witch hazel around Fresh Pond in Cambridge is in full bloom now right in time for Halloween. I never noticed the witches’ hats before.
Here are excerpts from Nature Observer Journal. A perfect Halloween story.
When you find Witch Hazel examine the few remaining leaves… often see a small cone that resembles a miniature witch’s hat. This is a Witch Hazel Cone Gall; the temporary home of a Witch Hazel Cone Gall aphid, Hormaphis hamamelidis. H. hamamelidis has a life as bizarre as the mythical hags that transformed themselves into frightening creatures to torment medieval travelers. In late fall female aphids lay eggs on Witch Hazel branches. In spring only female aphids (stem mothers) emerge. These produce a secretion that causes a wart-like malformation to form on the leaf…. cone-shaped and hollow with an opening on the leaf’s under surface. The aphid mothers then deposit fertile eggs in the cone… produced parthenogenically. When the next generation of aphids are mature they emerge from the cone and fly to a birch tree where they live as flightless insects and reproduce sexually for several generations. The sixth generation hatches with wings and flies back to the Witch Hazel to reproduce. Another generation of stem mothers hatches on the Witch Hazel and the extraordinary cycle begins again.