No, there is no such feature on the Mac. If you drop a folder to a place where there is a folder with the same name you will be prompted if you want to overwrite the folder.

To merge two folders together you need to use the DittoGUI application: http://www.ilike.co.nz/SoftwareDev/dittoGUI.html

Hope this helps.

Paolo

https://www.preta3d.com
FB: https://www.facebook.com/RealityPlugIn
Tw: @preta3d
G+: https://plus.google.com/106625816153304163119
The Reality Gallery: https://reality-plug-in.deviantart.com