If there is any connection at all, I think it would be a pretty weak one. Grasshoppers don't eat mosquitoes and mosquitoes don't (I think) feed off grasshoppers. However, these critters are quite sensitive to the weather: lots of rain favors mosquitoes and dry hot weather favors grasshoppers. A lot of little critters also have a cycle. Tent catapillars around where I live are on an eleven year cycle. In the valleys of the cycle, you won't see a single one all year. In the peaks, there is enough to defoliate large trees.