The Usurper, Bombus hyperboreus

Under the green of the tundra surface during an arctic summer, murder and slavery prevail. There are two species of bumblebees common on the High Arctic islands. The smaller of these species, Bombus polaris, leads a typical bumblebee lifestyle. Each spring, an already-mated queen emerges from the frozen ground, and builds an underground nest, or uses an abandoned mammal burrow. Into this nest she lays a batch of eggs, which hatch into sterile females, worker bees, that assist the queen in rearing a second batch of eggs, which develop into reproductives – queens and drones. While this basic chain of events is the same as in more southern species, there are differences. In the longer summers of temperate regions, founding queen bumblebees are able to lay several batches of eggs that develop into workers. As a result, southern colonies become much larger, and can subsequently assist in the rearing of more queens and drones. By comparison, B. polaris queens reign over tiny kingdoms!
The other arctic bumblebee, B. hyperboreus, is a bully, thief, and murderer. Lone, mated queens emerge from the frozen ground each spring, like their smaller counterparts, but instead of building a nest of their own, they seek out a growing colony of B. polaris. Entering the nest, the usurper attacks and kills the queen, and enslaves her daughters. Queens of B. hyperboreus produce no workers of their own; their offspring are solely queens and drones. The captured workers of B. polaris live their lives caring for the young of an entirely different species.