Within the genus Megachile, frequently also referred to as leafcutter bees, M. campanulae is a member of the subgenus Chelostomoides, which do not construct nests from cut leaves, but rather from plant resins and other materials.

Typically the females build small nests in pre-existing holes in trees, fences, or plant stems.

The female bees survive for another few weeks, during which time they build new nests and gather provisions.

[11] Similar to honeybees, female bees perform nearly all essential tasks of brood rearing.

M. campanulae does not produce honey, but does perform other important beneficial tasks, pollinating crops and wild plants.

However, the mandibles of M. campanulae lack cutting edges;[5] it belongs to the subgenus Chelostomoides, which use mud or resins to build.

[8] In the wild, M. campanulae seal off their cells within the nest with natural resins found in plants and trees.

[17] Since some of the bees were free of parasites, these novel and possibly more robust methods of nest building may offer additional protection.

[18] Incorporation of plastic into the walls and sealants of the cell nests appeared to provide some protection against brood parasite invasion.

In fact, exposure of brood to polyurethane and polyethylene based plastics could be detrimental, as the Canadian team noted, since diffusion of moisture could be inhibited.

[18] Additionally, synthetic materials in the nest might hinder the bees ability to move and breath.

[15] Toxin exposures and other effects of urbanization are well documented contributors towards pollinator decline in general.

[19] The range of M. campanulae covers a broad expanse of the eastern North American continent.

The mandibles in these resin gathering bees are characteristically lacking cutting edges found in the closely related leafcutters.

One each side of the midline, there are distinct ridges (tubercles) located along the margin of the lower facial plate (clypeus).

There are minute and closely spaced punctures on the skeletal plate covering the costal vein of the wing (tegula).

[3] The second through fourth dorsal segments, or terga, are elongated and parallel to each other in orientation, separated by deep grooves.

There are pale hairs covering the posterior edge of the sixth segment densely enough to hide the surface.

[3] There are short, white pubescent hairs sporadically distributed along the lateral and posterior aspects of the mesosoma.

The lateral aspects of the propodeum are generally of a smoother texture, although there are crisp and shallow markings closely spaced.

[3] The subspecies Megachile campanulae wilmingtoni (Mitchell) is characterized by larger size 11–12 millimetres (0.43–0.47 in), dark pubescence present on the 6th tergum, and darker wings with a brownish tinge.

[23] Mold growth was shown to be problematic in the Toronto study, particularly when synthetic materials were incorporated in nest construction.

These relationships are complex, involving issues of habitat loss, pesticides and toxin exposures, climate change, and other effects on the environment.

The significance of contributions from native pollinators is gaining increased attention in the wake of declines in managed bee populations.

In 2013, Oregon Congressman Earl Blumenauer introduced H. R. 2692 the "Save America's Pollinators Act".

[26] In addition, an International Pollinator Initiative has been developed by the Food and Agriculture of the United Nations working group.

[27] A similar project, the North American Pollinator Protection Campaign might more directly address issues specific to M.

[28] On a smaller scale, human behaviors adversely affecting populations of bees, such as M. campanulae, can be mediated in other ways.

[29] Since native pollinators forage in an area within about 500 yards (460 m) of the nest, they can increase the productivity of a small garden.

Bees can be harmed by numerous classes of pesticides including: insecticides, fungicides, herbicides, acaricides, rodenticides (coumarins).