A more thorough explanation:

Per insidias et industriam (pronounced pər in-sid-ee-əs et in-dəs-tree-əm) is a Latin phrase that means "by stratagem and on purpose; intentionally."

• He planned the surprise party per insidias et industriam, making sure to keep it a secret from the birthday girl.
• The company deliberately misled investors per insidias et industriam in order to boost their stock prices.

These examples illustrate how the phrase per insidias et industriam is used to describe actions that are done intentionally and with a specific purpose in mind. In both cases, the actions were carefully planned and executed in order to achieve a desired outcome.