It's amazing how many things live in and on rotting logs. Learn about insects and their roles in decomposition as you explore life in a rotten log. Before searching for your log, research the process of decomposition. Next, locate a rotten log and carefully begin inspecting it. Note any markings or holes found on the log's exterior.
Many beetles can create beautiful patterns as they bore into the wood.
Pull apart the log. You should encounter many insects and other arthropods such as spiders. Be sure to make drawings and to note characteristics of each organism you see. Use these notes to identify the animals later using a field guide. If you really want to know, you can do a simple population count.