With additional investment from MCFC, we were able to purchase summer nesting units. When the first leafcutters begin to emerge, we take the Spring red mason nesting blocks out of the solitary bee boxes and store them over Winter. The cocoons will be removed, cleaned and kept safe until they can be put back out again next Spring, when the whole cycle can start over again. The Summer units have larger 8mm diameter nesting holes for leafcutters and very small 3-5mm diameter nesting holes for yellow-face bees and tiny parasitoid wasps.
We have two frequently common leafcutter Spp at CFA, Brown-Footed Leafcutter (Megachile Versicolor) and Willughby’s Leafcutter (Megachile Willughbiella). Almost immediately, one of these species has started nesting in the new units (time will reveal which one) but hopefully there is time for many more nests to be completed. Female leafcutters use their sharp mandibles to cut perfectly round holes from the leaves of preferred shrubs (Rose is popular, in my garden they use Pyracantha). They will then use these discs to form a cigar-like cell which the female provisions with pollen, lays an egg and seals with more cut leaves. The accuracy and precision of this procedure cannot be overstated, with each cell interlocking with the next. Leafcutter bees are targeted by sharp-tailed bees in the genus Coelioxys, which will try to breach the leafcutter nest to lay its own eggs there. The sharp-tailed bee grub will then go on to devour the leafcutter pollen supply and larvae.