Do you know what this is called? It always hangs on the wall. Reptiles don't know where they came from. It always appears endlessly several times.

According to the information you provided, this bug is called booklice. Booklouse is a common indoor insect. It likes to live in a humid environment, so it may often appear on your wall.

In order to deal with this bug, you can take the following measures:

1. control indoor humidity: booklice like humid environment, and their reproduction can be reduced by controlling indoor humidity. Dehumidifier or air conditioner can be used to reduce indoor humidity.

2. Clean the wall: booklice may crawl on the wall because there are food scraps or dirt they like on the wall. So you can clean the walls regularly to remove dirt and food residue.

3. Use pesticides: If there are a large number of booklice, consider using pesticides for treatment. Please pay attention to choose pesticides suitable for indoor use and use them according to the instructions.

4. Prevent pests from happening again: booklice may be carried indoors, and measures should be taken to prevent pests from happening again. For example, clean the indoor environment regularly to avoid excessive humidity.

I hope these measures can help you solve the problem. If the problem still exists, it is recommended that you consult a professional pest control expert.