Tracing the evolution of one major type of beetle, the weevils, shows how the number of weevil species exploded when some of them stopped eating primitive plants like cycads and conifers. Dr. Brian D. Farrell, a curator at the Museum of Comparative Zoology at Harvard University, has shown that those groups of beetles that long ago evolved to eat flowering plants spun off thousands of species, many more than those beetles that continued to eat more primitive and less diverse plants.