How do you know there is a correlation between physical variables in the ecosystem and the stink bug population?

The way to know there is a correlation between physical variables in the ecosystem and the stink bug population is:

Explanation:

The physical variables like weather, humidity or solar brightness, can affect the populations of living beings, especially the bugs, because they're directly environmental indicators, I mean, when the environment suffers alterations, the bugs quantity can show if that alteration is positive or negative, In the case of the stink bug, suppose that their ideal temperature is 10°C (weather), if the temperature increases or decreases from this value, the population securely going to decreases because they're are not in their ideal temperature. then, each time the population of the stink bug is altered, you can identify that a physical variable was modified in that period time.