Taurus Scarab Beetles (IMAGE) Northwestern University Caption A new mathematical model developed by Northwestern University researchers explains why two distinct subspecies evolve in ornamented animals: one with flashy, "costly" ornaments for attracting mates and one with subdued, "low-cost" ornaments. Here, two male taurus scarab beetles, a type of dung beetle, illustrate the subdued subgroup (left) and the showy subgroup (right). Credit Douglas Emlen, University of Montana Usage Restrictions Include credit. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.