This dome shaped and green colored mass is Green Slug Caterpillar (Eloasa symphonistis), in the family Limacodidae. This slow moving caterpillar feeds on the leaves of Acacia and some plants in the family Rhamnaceae. They have a number of pale lines running along its body. The caterpillar you see here was feeding on Ziziphus mauritiana leaves.
Green Slug Caterpillars (Eloasa symphonistis)