How to remove selected elements from a QGIS legend?

I'm working with a QGIS project with a number of layers. When assembling a printout all visible layers are automatically added to the legend:

I would like to exercise some control over the legend elements are remove some of the entries:

However, as the entries correspond to the upper levels in the hierarchy, deleting them will remove the keys:

1 - 20000
20000 - 40000

I'm working in Qgis 2.8. I'm not interested in modifying my layer structure but only in changing the legend elements.

Instead of deleting legend items, you could hide them. From the Legend items options window, right-click the name of the layer and select the Hidden option:

This would hide the names of layers, leaving the values:

Hope this helps!