Macs do not recognize Android devices by default. You will have to use an application that will allow your Mac to recognize the android device that you want to connect to it. Below is the recommended application if you want to connect your android to your Mac.
Android File Transfer
How to use it:
1. Download the app.
2. Open androidfiletransfer.dmg.
3. Drag Android File Transfer to Applications.
4. Use the USB cable that came with your Android device and connect it to your Mac.
5. Double click Android File Transfer.
6. Browse the files and folders on your Android device and copy files up to 4GB.