This is a problem that commonly presents itself in mixed species exhibits. I think you would need a better habitat for a land dwelling frog. At the very least, do a half and half style set up with the land portion having substrate and plants (fake or real doesn't matter) so that the frog will have a good place to hide and the crickets would have a place to stay even though they will probably commit suicide anyways (even in a cage with 95% land, they find their way into a water bowl).
