are Silver Beetles, commonly referred to as SB. Silver beetles are a basic in-game currency which can be used to buy items from NPC shops, upgrade your Territory, participate in player trades, and many other things.
As of 26 April 2013, if a player has at least 5000 SB on hand, you will be unable to earn SB through exploring or NPC battles however you can gain more SB through player trades and selling to the Monkey Business.
Please note that it is against the rules to use the Trading Center as a bank.
SB can be gained in many ways: