I stumbled upon this scientific paper in which they say that that

different earthworm species are impacted differently by C-to-N ratio and feed mixture type.

For the Eisenia fetida (tiger worm) the result of their study was:

A C-to-N ratio of 25 resulted in the highest stability of the product, the best fertilizer-value of the product, and also a product with the lowest potential for environmental pollution

I stumbled upon this scientific paper in which they say that

different earthworm species are impacted differently by C-to-N ratio and feed mixture type.

For the Eisenia fetida (tiger worm) the result of their study was:

A C-to-N ratio of 25 resulted in the highest stability of the product, the best fertilizer-value of the product, and also a product with the lowest potential for environmental pollution