Placing classic mothballs in a container near items that need to be protected from small creatures is one method, but keep in mind that those chemicals are quite toxic; if there is any possibility of access by children or pets, don't use them. Mothballs also work much better in an enclosed space, which your open-bottom cover does not provide. Such covers also are unlikely to prevent entry by rodents, which can cause far more damage than insects.
What you need is a simple made full enclosure, something a handy man can make with some triplex/plywood boards and some other not so expensive materials. Of course you need to ask if the owner of the apartment will allow you to put something like that at the motorcycle parking location....
I have the motorcycle I always dreamed of, a Kawasaki ZR14R. Problem is, the motorcycle has to stay outside as my apartment has no enclosed parking for motorcycles. I have a cover that does a fairly good job, but what other steps can I take to discourage spiders, moths and other creepy crawlers from taking up residence under the motorcycle cover?