Chelostoma florisomne, the large scissor-bee, is a species of hymenopteran in the family Megachilidae.

The Latin species name florisomne refers to the habit of some males to sleep inside the buttercup flowers.

The area of distribution covers most of Europe (Austria, Belgium, British Islands, Czech Republic, Denmark, Finland, France, Germany, Hungary, Italy, Lithuania, Luxembourg, European Russia, Poland, Slovakia, Slovenia, Spain and Switzerland) and North Africa.

[2] These bees occur in forests, meadow, slopes and orchards, where buttercups (Ranunculus species) are present.

The females usually build their nests in old beetle burrows found in dead wood, but they also may use hollow plant stalks.