Leaf Cutter Bees are similar in size to the ordinary honey bee - but usually more hairy. They are solitary living bees and do not swarm or gather in groups. They are darker coloured than ordinary bees, but with bright yellow banding of the abdomen.
The damage they do to leaves is normally semi-circular chunks cut out of the leaf edges. They carry the cut out bit to make their nests - not simply eating the foliage.
They are harmless unless handled - rarely stinging unless severely provoked.
They nest in rotted wood debris, or the thick pithy wood of old roses - tunneling into the centre and often leaving a fine sawdust trail behind. This is rarely damaging to the rosebush.
The pieces they cut out of leaves - often roses - are normally semi-circular and about 10-15mm in diameter. This is then used to 'pad' their nest - dividing it into individual cells for the hatching young.
There are a range of natural parasites for this particular pest, so it is rare to have an infestation of any consequence. Insecticides are rarely required.