Thank you friends for your trying to help. But none of the suggestions worked. In fact I had already tried those before writing to the mailing list. Finally one of my friends (not in mailing list) suggested me to install 'shotwell' ( https://archlinux.org/packages/community/x86_64/shotwell/), and it solved the problem. After installing 'shotwell', when I made the camera 'on' after connecting to my PC's USB the camera got mounted and the icon came up on the Desktop. I reported it here as an information service. Thank you all. Shotwell is a pictures browser, unrelated to handling cameras by the file manager or desktop environment. It seems to be a coincidence caused by installation of one of the dependencies of the shotwell package. Therefore the issue is not solved.
Of all its dependencies the only ones I see, that do relate to photos access and wouldn’t be installed already on Arch Linux as the base dependencies, is libgphoto2 and whatever it needs. Which would be installed as a dependency of gvfs-gphoto2 suggested above. 1) If you open access to the camera, what is the path to its mountpoint? The one displayed by the file manager. 2) Is this actually Arch Linux? Not “Arch derivative”?