“The blue tit had found its food in a gall among the branches of the wild rose.
It was bitterly cold, not an insect flying, not an earthworm peeping out of the ground, yet the bird had known by instinct that something inside that gall would have let it survive one more day.”
(Mario Rigoni Stern – Stagioni, 2006)
The female Diplolepis rosae (Hymenoptera) lays its eggs in a leaf bud on the wild rose. This induces the plant to grow a ball of thin and ruffled filaments (robin’s pincushion), hiding the tiny larval cells at its base. The grubs overwinter inside the gall and emerge from their shelter the following Spring, unless in the meantime a cold and hungry bird has discovered them in their hideout.
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