The benefit of Black Bugs, however, is that they are free; they do not cost Coins or Pearls. One Black Bug is generated every 5 minutes, but a player can only have 10 of them at any one time. If a player does not have 10 Black Bugs already and they are selected as the current bait, a countdown timer will show in the corner of the bait icon showing when the next Black Bug will be received. During a previous version of the game, 25 Black Bugs could be accumulated instead of just 10.
A common strategy is to use Black Bugs to build up Luck, then switch to better bait to use with the luck bonus. This way, the luck bonus is not wasted on inferior bait.
"These little black bugs can be found everywhere. Unfortunately, these bugs can't be used to catch Rare or Legendary creatures."