We have a lot of leaves avalible, do the bugs in the leaves damage the plant when put on the soil?
The simple answer is no. I think most gardeners over-think things like that and forget that plants are nature, and they've formed to work with insects and animals. I've personally never seen anything negative coming from using leaves as mulch.
The not-so-simple answer comes when talking about non-native species, both plants and insects. Having either plants or insects that aren't from here often causes imbalances that lead to more plant damage or higher populations of insects that don't have natural predators to keep their populations controlled.
It's best not to put all bugs in one category. There are good ones, bad ones, great ones, awful ones, and of course the ones that
seem bad but aren't - the ones that do visual damage but don't harm the plant at all. Far more often than not, insects and plants go hand in hand.