Leaf Galls

Very furry little galls on the upper surface of a leaf. From a distance they look like caterpillars. Galls are formed from plant tissue in response to the presence of larvae injected into the leaf. They may be flies, wasps or Lepidoptera. Galls are arthropod species specific and not necessarily plant specific (the same plant, especially Oaks, can have many types of galls). These galls are covered in long silky hairs, whereas the leaf surface is only slightly fuzzy. The genetics behind this often drastic change in plant structure in response to parasitism must be very interesting.