My parents were kind enough to humor me and let me install a bee house in their yard two years ago. Today, their Flora, Indiana bee hotel has become very popular with the area's wild bees.
Dad's bee house started as a ramshackle affair I constructed out of a wooden box purchased at Goodwill with an expired license plate for a roof. (I love the idea of those little bees sleeping under a tin roof.)
I introduced blue orchard mason bees to the house in the spring and alfalfa leafcutters in the summer of 2015, but had no luck enticing the emerging females to stick around and nest.
In 2016 we introduced these spring and summer bees again, and once again, had no nesters in April or May. In July, Dad called to report lots of bees flying in and out of the house. I went for a visit expecting to see many happy little alfalfa leafcutters nesting but was surprised to see an unknown species of very large leafcutter bees had moved in. These leafcutters were approximately 3/4" long, which is much larger than the alfalfa leafcutter bees I had introduced. And they were rambunctious! They cut big, jagged leaf pieces and bumped into each other a lot more than the other leafcutters. Alfalfa leafcutters are small and almost dainty, but these bees are more like Mack trucks.
I submitted photos and a description to bugguide.net with a request for identification. and within two days the wild bees had been identified as megachile pugnata, also called the sunflower leafcutter bee.
I opened several of the nesting tubes of "Dad's bees" last winter and found they have a much different nest structure than alfalfa leafcutters. The photo below is a comparison of an alfalfa leafcutter bee nesting tube and this wild leafcutter bee.
The females do not make egg chambers with the leaf pieces they cut and collect, as do alfalfa leafcutters. These bees chew up the leaves and combine them with clods of dirt and some whole leaf pieces to construct walls and seal the end of the tubes. The egg chambers are also spaced further apart than alfalfa leafcutters.
Rita, a bee enthusiast in Brookston, Indiana, was also seeing these bees in her nesting box. Rita sent photos of the bees and reported, "I have some that are much larger than others, but they all seem to be using the same size tubes, and look the same once filled."
Sunflower leafcutters were also present in my nesting boxes here in West Lafayette this summer. I was able to take this video of one cutting a section from a redbud seedling.
The larvae spin a cocoon that is attached to the inside of the tubes and if we open the tubes, the cocoons tend to tear - so I don't open them. Instead, I keep these tubes together in a paper bag in the unheated garage all winter and just put them out in the nesting house at the same time I start putting out the alfalfa leafcutter cocoons. Once they have emerged, I make sure the tubes are empty then dispose of them.
This is the first documented wild bee to nest in one of our nesting houses and it's been found in Carroll, Tippecanoe, and White counties. Sunflower leafcutter bees are considered manageable pollinators for sunflower crops and a great deal of research has been published on that topic. You can download a full .pdf here to read more about them and learn how they make their nests.
Are you raising solitary bees? Have you had local wild bees move in? I would love to hear about your experiences.