By Linda Zielinski
70 degrees brings another helpful pollinator to your garden: the Western leafcutter bee. These adult bees began as eggs last summer in dead stems, holes in wood created by other insects, or in tunnels formed between pavement stones. When air temperature stays consistent at 70 degrees, metamorphosis takes about 42 days for the pupa to become an adult bee. If the temps are more like 84 degrees, it takes only 20 days! As with other native bees, male leafcutters emerge a few days before the females, and hang around near the nest waiting for the females to emerge. They mate, and the males die shortly after. Short life, but sweet! Well, purposeful, anyway.
Finding perfectly round or oval-shaped holes in leaves in your garden means that you've been successful in providing nesting materials for the leafcutter. The photo shows fireweed leaves in my own garden, with evidence of a female creating supplies for one of her brood chambers. She only lays 30 eggs total, in a period of 4 to 6 weeks.
The female takes about one day to create a chamber and find pollen and nectar for that day's egg. Each chamber is built with oval shapes on the sides, and a round shape on the bottom, and also for sealing the top after the egg has been laid.
I was lucky to spot a leaf cutter bee half-way into her job of cutting an oval shape out of the leaf of a fireweed. It took her about another minute to cut out the other half; she tucked it under her body to fly off into the sky. She'll use the ovals around the edge of her brood chamber.
I didn't have my camera, but was able to find this photo of a leafcutter bee (Megachile perdita) heading toward fireweed, captured by iNaturalist member Kris Ethington last August. Notice how the abdomen is slightly lifted, one of the features of the leafcutter.
If you find evidence of leafcutter bees dwelling in your yard, please add a comment, and maybe a photo, explaining the type of plant.
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