After insects, Which living being is second largest in population?

Question

After insects, Which living being is second largest in population?

Answer 1

Plankton's the soul and sole food for the sea creatures

Answer 2

To do a comparison you need to specify what level you are talking about.  Likely the largest living beings in population are the protozoa.  This Phylum includes most of the microorganism.  The second largest would be the Phylum Arthropoda which includes the spiders and the insects.  But I suspect you were thinking which group has the largest number of species, that is usually considered the Insects.  Which is a class of Arthropoda.  I can only guess at the second largest number of species and that would also be a class of Arthropoda, the spiders.