Megachilidae

Definition

A cosmopolitan family of mostly solitary bees (Hymenoptera: Apoidea) distinguished by carrying pollen on a dense ventral abdominal scopa rather than on the hind legs, and by an elongated labrum. The family includes mason bees, leafcutter bees, carder bees, and resin bees—names reflecting their diverse nest-building materials—as well as kleptoparasitic species that lack scopae and exploit pollen stores of other megachilids. Their energetic, swimming-like movement within flowers enhances pollen release and makes them significant pollinators in both natural and agricultural systems.

Etymology

From Megachile (type genus, Greek megas 'large' + cheilos 'lip') + -idae (family suffix)

Example

The alfalfa leafcutter bee (Megachile rotundata) is a managed megachilid pollinator in North American seed production; females cut circular leaf pieces to line nest cells in preexisting cavities, provisioning each cell with pollen carried on the abdominal scopa.

Related Terms

• Apoidea
• scopa
• kleptoparasitism
• solitary bee
• pollination
• Megachile
• Osmia
• Anthidium
• Hymenoptera
• nest cell

Usage Notes

The abdominal (rather than leg) pollen-carrying structure is the key diagnostic trait distinguishing Megachilidae from most other bee families. The common names 'mason bee' and 'leafcutter bee' are ecological descriptors, not formal taxonomic ranks; both include genera outside Megachilidae (e.g., some Osmia are mason bees but some authorities place related genera in other families). Kleptoparasitic megachilids (e.g., Coelioxys) are often called 'cuckoo bees' and can be recognized by their reduced or absent scopae and pointed abdomens adapted for inserting eggs into host nests.