In recent years, significant advances have been made in understanding the systematics and evolution of arachnids. This virtual issue, launched to coincide with the 19th International Congress of Arachnology in Taiwan in June 2013, comprises 12 important studies on arachnids from Invertebrate Systematics. They include the description of a new Afrotropical family of Laniatores harvestmen (Pyramidopidae); a phylogenetic analysis of mite harvestman (Stylocellidae); phylogenetic studies on various groups of spiders from the Dictynoidea, Leptonetidae, Linyphiidae, Lycosoidea, Mimetidae, Nephilidae, Pisauridae, Psechridae and Theridiidae; and an exploration of the taxonomy and phylogeny of subterranean schizomids. These papers encompass studies undertaken in Africa, Australia, Europe, south-east Asia and North America, and several combine morphological and molecular approaches. Together, the publications in this virtual issue reveal key aspects of the systematics, biology and biogeography of these invertebrate animals.