Recently, GoodEarthGardens Lady (“Hi, Gerry!”) wrote about solitary bees, and I thought I'd buzz along (see what I did there?) and add my two penn'orth about leaf cutter bees, a subject dear to my heart ever since I discovered them in my plant pots, a couple of years back.
Even if you've never seen a leaf cutter bee, you have probably seen their work: the females neatly cut an oval from the leaf, leaving it looking as though someone has gone mad with a large hole-punch.
For some reason they are particularly taken with Rose foliage - one of my Clients was most miffed to find her L.D.Braithwaite had been perforated! - although they also cut discs from Wisteria and a couple of other plants.
Having carefully removed the section of leaf, they then take the ovals back to their nesting site - which in my garden, means some of my plants-in-pots-ready-for-sale, grrr grrrr - and dig a tunnel down into the soil, several inches deep.
The ovals of leaf are dragged down the tunnel to the bottom, glued together into a cigar-shaped cocoon, and the leaf-cutter bee then lays an egg in the cocoon, adds some pollen by way of breakfast for the new bee, seals it up and reverses out. She does this several times, until the tunnel is full, then she goes away and leaves them.
Come next spring, they hatch out into new bees! But the really clever part is that the top-most cocoon hatches first, followed by the deeper ones in sequence, so they each clear the way for the next one.
The photos - sorry about the quality! - show one of my plants, depotted, with a series of five cocoons in it (helpfully ringed in red), and a dissected cocoon showing the layers of leaf ovals, and the white grub at the centre, which might seem like a cruel thing to do, but when I did it, I had no idea that I would find a living creature at the centre, so don't worry, I have already suffered pangs of guilt over that one...
Although the damage to the leaves looks quite dramatic, it doesn't harm the plant much, and they soon re-grow new leaves, so if you find these neat, nearly-round holes in your roses, don't worry about them, but instead be glad that you have a hard-working solitary bee somewhere nearby!