One of my American plum trees (Prunus americana) is poorly sited–it doesn’t get enough sun. Consequently, it is attacked by aphids almost every year. (Plants that are happy in their location tend to be healthy and resistant to insects and disease. Poorly sited plants are much more likely to have problems.) Because ladybug larvae eat aphids, ladybugs immediately arrive to lay eggs on the plant. Most insects choose an egg-laying location where there is abundant food for their larval stage. The way I know that one of my plants has aphids is that I see ladybugs.
Right now most of the aphids are gone and the tree is full of ladybug larvae and pupae. Here are pictures of those two stages:
I don’t see any eggs or adults anymore. No doubt the adults fly away as soon as they hatch to find mates and other insect infestations to clean up for some lucky gardener.