A species of insect is newly introduced into the United States from the Philippines. This insect becomes established, laying its eggs on the leaves of oak trees. How can a biologist determine if the relationship between the insect and the oak tree is commensalism, mutualism, or parasitism?

If the insect benefits and the tree neither benefits nor is harmed, the relationship is commensalism.

In commensalism, one organism, the commensal, benefits, and the other organism, the host, is apparently unaffected. Since the insect is gaining benefit and tree is neither harmed nor affected, this relationship can be investigated to be commensalism.