Gall on Salix Caprea leaf

A large gall on a Salix Caprea (Goat Willow) leaf, probably caused by a Pontania species sawfly.

From Wikipedia (http://en.wikipedia.org/wiki/Gall):

Insect galls are the highly distinctive plant structure formed by some herbivorous insects as their own microhabitats. They are plant tissue which is controlled by the insect. Galls act as both the habitat, and food sources for the maker of the gall. The interior of a gall can contain edible nutritious starch and other tissues. Some galls act as "physiologic sinks", concentrating resources in the gall from the surrounding plant parts. Galls may also provide the insect with physical protection from predators.

Insect galls are usually induced by chemicals injected by the larvae or the adults of the insects into the plants, and possibly mechanical damage. After the galls are formed, the larvae develop inside until fully grown, when they leave. In order to form galls, the insects must seize the time when plant cell division occurs quickly: the growing season, usually spring in temperate climates, but which is extended in the tropics.

• Biota
• Life
• Vitae
• Eukaryota
• Animalia
• Animals
• Arthropoda
• Arthropods
• Insecta
• Insects
• Salix Caprea
• Plantae
• Plants
• Magnoliophyta
• Flowering Plants
• Angiosperms
• Great Sallow
• Goat Willow
• Magnoliopsida
• Dicotyledons
• Hymenoptera
• Bees
• Ants
• Wasps
• Salicaceae
• Salix
• Willows
• Sallows
• Osiers
• Pussy Willow
• Tenthredinidae
• Common Sawflies
• Pontania

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