Organism of the month Aug08

Leafcutter Bee Leafcutter bees (Click to see full size image) are non-agressive,  so relatively much safer to observe than most other bees. This is partly because they are not colonial – they have no throng of thousands of sister worker bees to rely on and share the work. So to die in combat would be a massive loss, nobody else is going to get the shopping, feed the kids and do the home improvements… erm, I mean, they would greatly reduce their chances of reproductive success if they were very aggressive.

So what is their nest like? An individual female will find a hole, such as in wood or between stonework, and uses the cavity to establish a set of brood chambers. She gathers pollen and lays an egg with it, so the grub that emerges has a food supply. She then seals it off with leaf fragments, and starts another brood cell, seals that, starts another cell, and so on. Soon the hole will be filled up, and so the female bee sets off to find more holes and carries on until all eggs are laid – if all goes well.

Later the grub that hatches from the egg eats the pollen, and it pupates until the next spring. New adults emerge from the earliest cells first, chewing through the leafy seal. Each has to nip the backside of the sibling in front (blocking the way out!) to awaken it, and eventually they all find their way to the entrance.

Leafcutter bees in the British Isles belong to the genus Megachile. They are quite distinctive in shape and colouration, and they have bright, fiery orange fur underneath their abdomen. That’s where they carry the pollen. They are very useful for the garden because they are quite safe to have living right next to your plants or greenhouses (even inside commercial greenhouses!) and are prolific pollinators. The more you have the better, and you can help them to improve their numbers by providing nesting sites.

To attract solitary bees such as these, and the mason bees (Osmia spp) perhaps be less tidy when clearing things like fallen plant stems, dead wood piles, etc. Naturally they need pollen and nectar sources, and some of the best are early-flowering wildflowers e.g. dandelion, white deadnettle, selfheal, goat willow; and herbs are great, such as lavender, rosemary, marjoram, thyme, and borage and things like artichoke. But to really boost their chances of breeding, make or buy a bughouse with holes drilled to about 8mm – 10mm diameter.

Does a bughouse really work?

Sheepdrove bughouse

Click to see a bee

I’ve got a bughouse from Sheepdrove Organic Farm, and it’s worked well in a sheltered east-facing location, where it gets early sun but does not get too hot all day. That was the advice from Dr Chris O’Toole, who has written a book on the Red Mason Bee (Osmia rufa) and a book on bumblebees. He developed cylinders of tubes to house these small bees. The idea is that you can provide dozens of nest chamber sites all in one place, and that saves the female bee lots of energy, because she would normally have to find numerous disperse locations.

Watch the video!

See what these lovely bees are like by watching the short video clips on the Natureheads channel at YouTube – here’s the best one embedded for you to watch now.

Watch the other clips on the Natureheads channel at YouTube for ideas on Leafcutter bee homes, witness some territorial behaviour, and more…

Finally – can anybody answer this question? I have been watching Leafcutter bees at my bughouse and noticed there are 2 different sizes of the same species. Are the small ones males and the larger ones females? I haven’t seen the smaller ones bringing leaf fragments back to their hole.

copyright © 2008 Jason P Ball


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