Key to orders 1A All three pairs of abdominal appendages two-segmented, with a terminal vesicle and five setae ...... Eosentomata 1B Abdominal appendages I two-segmented with a terminal vesicle and three to four setae; those on abdominal segment II and III two-segmented, with a terminal vesicle and three to four setae, or uni-segmented, without vesicle and with one to three setae ......................................................................................................................... 2 2A Median setae present on meso- and metanotum................................................................................ Acerentomata 2B Median setae absent on meso- and metanotum .................................................................................... Sinentomata

Published as part of Galli, Loris, Capurro, Matteo, Colasanto, Elisa, Molyneux, Tony, Murray, Andy, Torti, Carlo & Zinni, Matteo, 2019, A synopsis of the ecology of Protura (Arthropoda: Hexapoda), pp. 155-164 in Revue suisse de Zoologie 126 (2) on page 156, DOI: 10.5281/zenodo.3463443