What effect does the threat of cuckoo invasion have on social bumblebee queens?

It acts as a selective pressure favoring better fighters or quicker brood defense establishment.

The presence of cuckoo bumblebees introduces a significant ecological factor into the environment of social bees, acting as a form of selective pressure on the *Bombus* population. Queens that are less capable of defending their dominance or establishing their brood quickly and effectively against a parasitic invasion are less likely to reproduce successfully. This dynamic inherently favors traits in social queens that enhance survival against parasitism, such as superior fighting ability or faster resource monopolization and defense mechanisms within the nest structure. This ongoing pressure contributes to the complexity of the community structure supporting both parasitic and social life cycles.