Gintama S02 E16 Rhinoceros Beetles Teach Boys that Life is Precious

"We're Odd Jobs Gin!"

Kagura's beetle was killed during a beetle fighting match. She tries to drag Gintoki and Shinpachi to go beetle hunting with her. That only succeeds when they know there is a high demand for the beetles - meaning they can make money of it. The trio encounters the Shinsengumi who also happens to be capturing beetles for reason unknown.