Those are two of the 4 "Kingdom" only allies. You spawn those resources when researching the "ally" techs in the diplomacy line.

As empire, in the cooperation line you will see some techs that spawn darklings, devils, and two other things I cannot remember. Because you are Empire you cannot ever make use of the spider's nest.

You can only build the spider nest on the spider resource. Upon researching the tech, atleat 1 of the unit spawning "camps" will spawn. Then you click on it and build upon it just as you did to build a farm on fertile land.