Triepeolus 
Long-horn Cuckoo Bees

In Minnesota, there are fifteen described species within the genus Triepeolus. Bees in this genus are cleptoparasitic (cuckoo bees). Their hosts include ground-nesting bees in the genera Melissodes, Eucera, Epimelissodes, and Dieunomia. A Triepeolus female enters an unoccupied host nest and lays an egg in a partially or fully provisioned brood cell. The first instar Triepeolus larva has sickle-like mandibles that it uses to kill the host egg or larva. After eliminating any competition for the provisions, the Triepeolus larva consumes the cached provisions as it develops within the brood cell. Triepeolus closely resemble bees in the genus Epeolus, and they can be difficult to tell apart. In general, Triepeolus are larger than Epeolus, but are generally medium-sized, ranging in length from 6 to 18 mm (0.25 to 0.7 inches). Epeolus have one host genus, Colletes; Triepeolus have hosts belonging to multiple genera.

Triepeolus have black integuments with white markings that are composed of scale-like flattened hairs. The legs are often but not aways red, and the rear edge of the thorax has two pointed axillae (projections). The females lack pollen-collecting structures.