Nesting biology: Nests of M. minutissima were found in three aggregations of preexisting holes in the ground on a shaded bank. Nests occupied an area of 30m2 and were concentrated at the upper portion of the bank. Most active nests were located toward the middle of the bank. The type of soil at the nesting site was sandy clay, dry, and loose.
Theexisting cavities used by M. minutissima in the soil consisted of tunnels that ranged from 1.7 to 27.5cm in depth and were orientated either perpendicular or at an angle to the face of the bank. Entrance hole diameter ranged from 4 to 7 mm. All tunnels were unbranched, except for six, which had short ramifcations and were signifcantly longer. Half
of the completed nests had a nest plug consisting of two types of leaf
pieces as distinguished by their shape and size - semirounded and oval. Remainding nests did not have a nest plug per se, but instead had a cell that was built close to the entrance and presumably served as
a nest plug.
The number of brood cells per nest ranged from 2 to 14 and it was signifcantly correlated with tunnel length. Cells were built serially
and with a tight fit to the tunnel wall, but occasionally were spaced and not continuous. Brood cells averaged 8.4 mm in length and were made of leaf pieces of three different shapes and sizes (large and small ovals, and semirounded). As observed in other species of Eutricharaea (c.f.,
Medler 1965, Kim 1992), M. minutissima used large oval pieces to make the cell cup and semirounded pieces to make the cell cap, although sometimes they also used small oval pieces for the latter. Leaf pieces
were stuck together and the number of each type varied among cells Bees cut leaf pieces from R. communis, one of the common plant
species of the area. It was located30m from the nest aggregation. (Alqarni et al, 2014)
Praz (2017) reports that Megachile minutissima nests primarily in existing cavities such as stems or beetle burrows and uses leaf discs to build its brood cells but these are sometimes omitted when the nest is located in cavities of small diameters, so that leaf discs are only used to build the cell partitions (Krombein 1969).