Are living insects in my laptop dangereous?

I would take the laptop apart as far as possible (remove the keyboard, etc.). It's likely you spilled something sweet into it and the ants are prospecting for food. You might want to remove all the keyboard caps (if your system supports this) and thoroughly blow out every speck of dust (and food crumb) and be sure everything is thoroughly dry. If the keyboard is sticky, you might have to totally disconnect it, clean it with distilled or deionized water and dry it completely before putting it back.

Yes, pests including Ants, BedBugs, etc do cause problems for any electronics, include laptops. They can die in the laptop causing problems, as well as possibly nibbling on components...

First, did you spill anything on or near the laptop? Try wiping down the outside of the laptop with an antibacterial wipes. Get some ant traps, and place them around the laptop.

Remove the battery, and power cord. Leave your laptop off, and then wait. See what happens, but unless your willing to disassemble your laptop, or have someone else do it, your going to have to resort to external traps of some kind.

I would almost suggest placing the laptop in a large 1 gallon ziplock, but I'm afraid the ants will be killed inside the laptop...