In insects, the activity of phenoloxidase increases near the site of injury where it not only helps in wound healing but also prevents infection. The present study discusses the regulation of phenoloxidase by age dependent mechanical injury in the silkworm. The experiment was conducted on 4th and 5th instar silkworms with single and multiple wounding. A drastic increase in the enzyme activity was observed in 4th instar caterpillars upon a single wounding. Conversely, less enzyme activity was observed in 5th instar caterpillars upon single wounding but this increased with multiple wounding. This reveals the age dependent control over phenoloxidase activity in silkworm that may be essential in the later instars to prevent any autoimmune effect caused by the enzyme. Controlling enzyme activity may be a significant evolutionary strategy adapted by the caterpillar to regulate the energy investment during 5th instar. The results of the present study confirm the probability of the presence of a novel mechanism which regulates the activity of phenoloxidase in caterpillars at different instars.