Z. P. Metcalf, Univ. of North Carolina, writes in Science #2701, p. 329: No one seems to have a very clear conception of the enormous number of species of animals living in the world today. An actual count of genera and species of Homoptera in the card catalogue of this order of insects in my laboratory shows that there are approximately 3100 genera and 30,000 species recorded. Perhaps from these counts of the number of species of Homoptera we may be able to get a real estimate of the number of species of animals that have been described. From various counts and estimates, I believe that the Homoptera represent from 1/100 to 1/150 of the Animal Kingdom. This would give us an estimated total of 2,500,000 species of animals already described, of which 1,500,000 are insects.