How to keep spider and little bugs out of the vent that are coming through the basement?

I live in a rental how that has a basement. There are spiders and centipedes, earwigs and other tiny bugs coming through the vents and I don't want them coming in through the vent at all. I want to know what could I do to get rid of them or what can I put in front of the vent so then don't get in. Please help me!! I hate bugs and especially spiders!!!!!