Read the title!
Read the title!
They're from Thaumic Bees, and they produce Iron Nuggets and Honeycombs. They're pretty useful.
the bee mod is called Forestry, with (in Ultimate) addons Extra Bees and Thaumic Bees.
There are bees for every metal in the game, all the way to tungsten. If you wish to keep the world fairly untouched you might want to consider massive beefarms with all the metallic bees gathering you resources. In our FTB-server we've resulted gathering copper via copper bees since it's fairly rare and it's used a lot in the late-game machinery and automation. 20 Apiaries with fast copper bees produce about 10 stacks of copper a night, fully automated this produces a fair amount of honey on the side as well.
If you go to the new site, there is a LOT more info on bees.