Insect eating bats and their teeth?

If these wonderful little guys just eat mosquitoes. which I have been told they do here in Michigan, why do they have such pronounced incisors? I mean all the teeth are very small but relative to the other teeth they were larger. Had another of these beauties in the house again last night. He hung from the ceiling for a couple hours and watched me while I wrote kind of wonderfully eerie. Anyway before I went to bed I used work gloves to gently grab him and send him on his way outside. Had a chance to study him a bit and noticed the incisors. Thanks