MARTYN F. CHILLMAID / SCIENCE PHOTO LIBRARY MARTYN F. CHILLMAID / SCIENCE PHOTO LIBRARY
This common rose gall is formed when the tiny gall wasp Diplolepis rosae lays up to 60 eggs in the rose's leaf bud in summer. Exactly what the process is that forms this intricate nursery nest for the growing grubs is still unclear, but it is assumed that the wasp or its grubs produce a chemical that causes a growth reaction within the leaf bud similar to a benign tumor. The grubs, eating plant tissue in their protective chamber, feed until winter and then pupate, emerging as adult wasps in May. The gall starts off green with sticky filaments, develops its red colour in the autumn, and then turns brown and dry over winter.
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