The larval stage of several insects cause damage to home lawns. The larvae feed on roots and underground stems of grass. A thick, healthy lawn may not be resistant to insects, but will be better able to recover from injury and will be able to tolerate some damage without it being noticeable.
If you suspect insect injury, look closely in the thatch layer and top 1-2 inches of soil for larvae. Make sure you have correctly identified the insect and understand its lifecycle to determine the best course of action for control.