big fleas have little fleas upon their back to bite 'em

The phrase "big fleas have little fleas upon their back to bite 'em" is an expression that highlights the concept of hierarchical relationships or the idea that there is always someone or something smaller or lesser that can cause harm or exert influence on those higher up in the hierarchy. It implies a cascading effect, where even those who seem powerful or dominant can be vulnerable and affected by others who are subordinate. In essence, the phrase suggests that no matter how big or important a person or entity may be, there is always something or someone that can challenge or undermine them.