Trachusa

Trachusa are small to medium-sized, stout megachilids. Due to their great variation across the Old World, there are few clear morphological characters that can be used to describe this genus unambiguously. Typically, the back of their heads is rather large, and they have robust legs, with the hind and middle tibia almost equally broad. Coloration and pilosity vary greatly depending on the species. Some species are completely black while others have yellow markings. Females have ventral scopae and rather large mandibles, usually with three to four short teeth. The abdomen of the males has a very characteristic shape. It curls slightly inwards at the tip, and, in certain species groups, it also has black combs underneath. They are ground nesting bees that dig their own burrows in the soil. Brood cells and their partitions are commonly made of resin and cut leaf pieces.