  For complex connected, reductive, affine, algebraic groups $G$, we give a
Lie-theoretic characterization of the semistability of principal $G$-co-Higgs
bundles on the complex projective line $\mathbb{P}^1$ in terms of the simple
roots of a Borel subgroup of $G$. We describe a stratification of the moduli
space in terms of the Harder-Narasimhan type of the underlying bundle.
