1.3.1. The described taxonomic richness of insects

Probably slightly over one million species of insects have been described, that is, have been recorded in a taxonomic publication as “new” (to science that is), accompanied by description and often with illustrations or some other means of recognizing the particular insect species (section 1.4). Since some insect species have been described as new more than once, due to failure to recognize variation or through ignorance of previous studies, the actual number of described species is uncertain.

The described species of insects are distributed unevenly amongst the higher taxonomic groupings called orders (section 1.4). Five “major” orders stand out for their high species richness, the beetles (Coleoptera), flies (Diptera), wasps, ants, and bees (Hymenoptera), butterflies and moths (Lepidoptera), and the true bugs (Hemiptera). J.B.S. Haldane’s jest — that “God” (evolution) shows an inordinate “fondness” for beetles — appears to be confirmed since they comprise almost 40% of described insects (more than 350,000 species). The Hymenoptera have nearly 250,000 described species, with the Diptera and Lepidoptera having between 125,000 and 150,000 species, and Hemiptera approaching 95,000. Of the remaining orders of living insects, none exceed the 20,000 described species of the Orthoptera (grasshoppers, locusts, crickets, and katydids). Most of the “minor” orders have from some hundreds to a few thousands of described species. Although an order may be described as “minor”, this does not mean that it is insignificant — the familiar earwig belongs to an order (Dermaptera) with less than 2000 described species and the ubiquitous cockroaches belong to an order (Blattodea) with only 4000 species. Nonetheless, there are only twice as many species described in Aves (birds) as in the “small” order Blattodea.

Chapter 1