Cuckoo bees are called “cuckoo” because they don’t forage for pollen to feed their young. Instead, they steal it. Female cuckoo bees hang around the nests of other bees and wait for an unguarded moment to slip inside.
Once there, the invader lays her eggs on the pollen provision that was collected by the host bee. When the cuckoo egg hatches into a larva, the larva eats both the brood and pollen of the host bee and then pupates just like the rightful inhabitants of the nest. In some species, the female cuckoo kills the brood before laying her eggs. In either case, the cuckoo female has no responsibility for her young. She just takes off and finds another nest to violate.
Cuckoo bees, known as cleptoparasites, are very common in the bee world. According to O’Toole and Raw (1999) twenty percent of all bees in North America—and nineteen percent of all bees in the world—fall into this category.
The bee shown below, which I found in Finley National Wildlife Refuge—is in the genus Sphecodes in the family Halictidae. This genus includes 72 species found in North America. Of those, 20 species are found in the Pacific Northwest region of the U.S. and Canada. These small sweat bees range in size from about 0.2 to 0.6 inches long but can deliver a nasty sting. The females have red abdomens while the males are all black. Both sexes have wide heads.
Nearly all the Sphecodes and their hosts are solitary ground-nesting bees. To make nest invasion easier, the cuckoos have evolved to look a lot like the hosts they prey on. Although they collect no pollen, they are often seen on flowers where they drink nectar to fuel their nefarious activities.