Concrete floor, cinder block wall -- how to fill gaps

I have googled this, but to no avail, and was hoping someone here would know the answer. My garage floor is a concrete slab, the walls are cinder block. There is a slight gap where the walls meets the concrete (perhaps 1/8 of an inch). I am not sure whether this was ever filled or whether I'm only just noticing the gap, but I would like to fill it in. Would I use a kind of silicone, mortar, or perhaps even grout to do this? I'm just not sure which material would last but still allow for expansion. Or should I leave the gap alone? I live in Florida. Moisture is not an issue, but bugs are. Any help would be appreciated. Thanks! KB