Arthropoda

Arthropoda are a large and diverse group of animals. According to Wikipedia, with over a million described species, Arthropoda are by far the largest group of living animals species. At the moment, we distinguish four subphyla: Chelicerata (spiders and allies), Crustacea (crabs and shrimp), Hexapoda (insects), and Myriapoda (centipedes and millipedes).

There are about 100'000 spider species, more than 1'000'000 insects. Within insects (data from http://www.catalogueoflife.org/ accessed 11/4/2017):

- Coleoptera 392'415
- Diptera 160'591
- Lepidoptera 158'570
- Hymenoptera 155'517
- Hemiptera 104'165
etc.

Only the kingdom Plantae (382'000), the phyla Fungi (140'000) and Mollusca (80'000) exist in similar numbers. All Chordata have about half of Hemiptera (a taxonomic group that is not even acknowledged with a proper name by a biodiversity expertise game).