Primæval Flies _Archiptera_ | Scorpions | Double-footed _Scorpioda_ | _Diplopoda_ Tailor Spiders | | | _Opiliones_ | | | | Book Scorpions | | | Mites | _Pseudoscorpioda_ | | | _Acarida_ | | | | | | | \-----v-----/ | | | | | | | | | Tarantella | | Weaving Spiders | _Phrynida_ | Simple-footed _Araneæ_ | | | _Chilopoda_ | | | | =Centipedes= | | | | +Myriapoda+ \-------------v--------/ | | | | | Scorpion Spiders | | _Solifugæ_ | | =Spiders.= | | +Arachnida+ | | | | | | =Flies= | | +Insecta Hexapoda+ | | | | | | | \--------------------v---------------------/ | Primary Air-breathing Arthropods _Protracheata_ | | Articulated Worms _Coelminthes_