How are .........?

Question

Using examples discuss the reasons why some insects are regarded as beneficial to agriculture and detrimental to agriculture

Answer 1

Aphids are regarded as detrimental to agriculture because they eat alfalfa and clover leaves.  Ladybugs are considered beneficial to agriculture because they eat aphids.

Answer 2

Insects that eat vegetation are general considered detrimental to agricultural production because they eat the crops.  Insects that eat other insects are generally considered beneficial because they control the other insects.

Sometimes an insect that damages the crops is required for production of that crop.  There is a moth that causes pollination of Yucca flowers, lays eggs in the blossom, and the larvae eats some of the seeds produced.  the Yucca cannot reproduce without the moth, and the moth cannot reproduce without a yucca flower.