The Jolly Beetles are insects native only to Swellview, and it can be implied they are a rare species of beetle. The evil scientist Dr. Minyak captured 15 of those rare beetles and having learned of their tears and their impact on molecular density, decided to use them to end Captain Man's career.
The beetles were trapped on chairs inside glass jars in Minyak's hideout and were manipulated into watching a really sad movie, making them cry yellow tears. Nurse Cohort would eventually use their liquid of tears and spray it in Captain Man's face, making him vulnerable to pain.
The beetles would continue to be under Minyak's control, until Kid Danger and Captain Man intervened and saved them, sort of (one beetle met his demise when Captain Man stepped on him). Gooch would let the beetles watch a funny show, making them cry tears of joy, and restoring Captain Man to his indestructible self.