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Megachile inermis (Leaf cutter bee)

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Taxonomy

This species is in the family Megachilidae. The genus Megachile is known by the common name “leaf cutter bees” because many members cut out circular or oval pieces of leaves and use them to line their nests. There are some exceptions; some Megachile use tree resin and others use masticated vegetation and mud in addition to leaf pieces. Megachile inermis were a less common bee in Bee Atlas blocks, but we did see small numbers of them every year. Almost all nests were from the northern half of the state, in the Laurentian Mixed Forest and Prairie Parkland biomes, although there was one nest in the southern part of the state in Dodge County.

Description

Megachile are pretty much all characterized by having large chewing mandibles, and the females carry pollen in a scopa under their abdomens. This species, like many Megachile, is a mostly dark bee with light hair bands across the abdomen of both females and males. Males have unmodified forelegs; they look like extra fluffy females with extra long antenna and no scopa (the pollen-collecting hairs on the underside of the females' abdomens). Megachile inermis is a very large Megachile, similar in size to a honeybee worker. Apart from their large size, they do not have a lot of distinguishing characteristics, but one clue is that the females' scopa is distinctly light haired. Bees range from 11-20mm long, with females over 15mm.

Nest Structure

Megachile inermis use leaf pieces to make their nests. Their plugs may appear as cut whole leaf pieces, or those pieces may be covered with some chewed leaves, bits of wood, or mud and sand (see graph in pictures). Sometimes the cut leaves show through this outer layer. We have been fortunate to open a few of their nests and find very neatly packed cut leaf pieces and cells. (see pictures)

Hole Sizes

M. inermis build nests in the largest holes (3/8"-7/16") in Bee Atlas blocks. (see graph in pictures)

Voltinism

As far as we know, M. inermis are univoltine in Minnesota, meaning they have only 1 generation per year.

Activity Period

Megachile inermis is active in the mid to late summer. Between 2016 and 2018, nests were most often completed from the middle of July to the middle of August in Bee Atlas blocks. (see graph in pictures)

References

No information at this time.

Minnesota Record Map

These data are from the Minnesota Bee Atlas project.

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