Based on the size I think this may be a species of Colobopsis (Arboreal Ant) but it may also be a type of Meat Ant (Iridomyrmex mayri). Did you notice any other similar looking ants nearby? Ants have major and minor workers with different appearances or any other behaviour traits. The Antwiki is a great resource https://www.antwiki.org/wiki/Colobopsis.
I think the blobs on the leaf are actually leaf galls.
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