AbstractThe monophyletic genusSolonaima, endemic to northern Queensland, is reviewed and six new species are described:S.sullivanisp.n.,S.pholetorsp.n.,S.stoneisp.n.,S.halossp.n.,S.irvinisp.n. andS. baylissasp.n. The previously known epigean species,S.solonaimaKirkaldy andS.pallesens(Distant) are illustrated and redescribed. The six new species represent four separate independent cave invasions and nearly double the number of known cavernicolous cixiids in the world. This is the first report of a closely related group of cave‐dwelling Homoptera showing varying degrees of cave adaptation. One facultative cave species,S.sullivani, shows virtually no modification from surface relatives. Two species,S.pholetorandS.stonei, show some eye, colour, and wing‐reduction, but they are still flighted and are considered facultative cave species.S.halosandS. irviniare nearly blind and have reduced, non‐functional wings and are considered obligate cave species.S. baylissa, the most remarkable obligate cave species, is highly modified: eyeless, nearly wingless and colourless. The evolutionary trends displayed in cave adaptation are illustrated and discussed. These include reduction in body colour, eyes and wings, alteration of head and thorax shape, and possibly simplification of the male genitalia. The geology of the caves is complex and ranges from greater than 5‐million‐year‐old caves in Silurian‐aged metamorphosed limestone to 190,000‐year‐old lava tubes. The facultative species are generally found in the most open caves, the two intermediate obligate species are found in deeper caves, and the most highly modified species is restricted to damp cave passages with high CO2levels. There is no correlation between the ages of the caves and the degree o
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