Usechus lacerta vs. Usechus nucleatus

The most noteable difference between these two species is the tubercles at the base of each elytra. On each species two elytral ridges come together to form a tubercle on each elytra. In U. lacerta these nodules are very reduced, not obvious and do not extend over the pronotum. U. nulceatus has more pronounced nodules that extend over the pronotum.