what kind of bug is on my holly bushes
It is causing the leaves to turn brown and die. The leaves on my holly bushes are covered with spider webs and black "eggs" that have turned the leaves brown and seems to have killed some of the stems.
There are hundreds of kinds of bugs that might be on your plants. However, it's possible that some disease is attacking your holly, and the bugs are just hanging around. This article will help you find more information about common diseases and insects: https://www.gardeningknowhow.com/ornamental/shrubs/holly/diseases-of-holly-bushes-pests-and-diseases-damaging-holly-bushes.htm
You can send us pictures of the leaves, and the bugs if you can find them.
Or you can take some leaf and branch samples to the County Extension Service for analysis. This link will help you locate the nearest one: https://www.gardeningknowhow.com/extension-search