Extension > Garden > Diagnose a problem > What insect is this? > General/curiosity insects > Insects with obvious wings: ¾ - 1 inch long >Blue mud dauber

Blue mud dauber

Chalybion californicum

Jeff Hahn, University of Minnesota Extension

Joseph Berger, Bugwood.org

Description: 3/4 - 1 inch long. Black with just a little iridescence.

Where/When: Constructs its nests in cavities in plant stems and in buildings. Carries water to a source of soil near its nest to moisten it so it can use the mud to build its nest; found June through August.

Significance: Not aggressive, stings are rare. Does not harm buildings where they build their nests.

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