What's the difference between "katika" and "ndani ya"?
They're largely synonymous, but ndani ya emphasises being in an internal space more than katika does.
This can also be "An insect pest in the mango". Any insect in a mango is considered a pest.
it would be either insect or pest, not both. And even then, 'pest' is a very general term meaning any unwanted creature (or person)
Is this a phrase like "a fly in the ointment"