Flick will pay you 3,750 bells for a wasp (compared to Timmy and Tommy’s price of 2,500 bells), while a tarantula will get you a whopping 12,000 bells. For reference, Timmy and Tommy only pay you 8,000 bells per — which is still significant, but an inventory full will land you a few hundred thousand bells.
Besides the Bug Off event, it’s unclear how often Flick comes to your island, but it looks to be with the same regularity that Saharah comes with her rugs and wallpapers.
Source : https://www.distractify.com/p/when-does-flick-come-animal-crossing